Marvel Carburetor Disection

[Jeff in BC]

Continuing with the idle system and the upper portion of the carb.



Photo 8 – Interior view of the upper portion of the carb.

At the center of the photo is the passage (10) where the idle well enters.



Photo 9 – View into passage (10) for idle well.

I removed the idle adjusting needle to shine a light in, as this passage is too deep to get a photo any other way. The threads for the needle can be seen at the bottom.



Photo 10 – View from top of carb with throttle valve (6) closed.

The bright dot (7) at the center is the tip of the idle adjusting needle; this is the primary idle orifice.

Now I removed the throttle valve.



Photo 11 – Throttle valve parts.

Note the wear at the ends of the throttle shaft (~ 0.010”). This may be a problem for rebuild (air leakage). Also there aren’t any seals.

Now back to the idle system.



Photo 12 – View from top of carb with the throttle removed.

The primary idle orifice (7) can be seen and just below is another orifice. This is the secondary idle orifice (8).



Photo 13 – Another view into passage for idle well.

The above shows a wire placed in the secondary idle orifice; below it are the threads for the idle adjusting needle.



Photo 14 – Idle adjusting needle.



Photo 15 – An attempt to show the fuel passages into the upper portion of the carb.

6 – Throttle Valve in closed position
8 – Secondary Idle Passage
7/12 – Primary Idle Passage/Idle Adjusting Needle Seat
10 – Idle Well/Passage
13 – Idle Adjusting Needle

There is one more passage to show, this is an air passage.



Photo 16 – Interior view of the upper portion of the carb showing the air passage (copper wire) into idle well passage with the gasket in place.

Note the small cutout in the gasket, this is important for correct airflow.



Photo 17 – Side view of the upper portion of the carb showing air passage.



Photo 18 – Diagram from Service Manual.

For an explanation of the Idle System refer to the TSX Service Manual page 3. A link to this manual is at the beginning of Post 1.

Now for a little fun.

How does this all fit in with the magic number, 1536043, on the side of the carb? Lets have a look at the patent. A link to this patent is at the beginning of Post 1.

On Figure 1 The primary idle orifice (54) and the secondary idle orifice (53) are shown and an explanation of their function starts on page 3 line 80 (correction page 3 line 43). Continuing on to page 5, starting at line 28, are claims made by the inventor, claims 1 thru 4 refer to this type of idle system.

The explanation given in the TSX Service Manual, on page 3, are a little easier to follow than the explanation in the patent. It should be noted that both of these explanations refer to an “Air Adjusting Needle Valve”. The carb we are looking at uses a “Fuel Adjusting Needle Valve”. There is an explanation of the differences in the TSX Service Manual on Page 8, lower left paragragh.

The next section to be covered will be the Power Fuel Feed System.

That’s all for now.
Jeff

[Jeff in BC]

Hi All

Here's the Marvel Carb schematic showing the idle system.



Jeff

[Jeff in BC]

Hi All

Well I’m back again with the fourth post.

The Power Fuel Feed System

For this system I will start by identifying some parts of the lower portion of the carb.



Photo 1 – Looking at lower portion of carb with gasket in place.

A - Lead Plug
B – Gasket Covering Passage
C – Note: Gasket does not cover the corner of the fuel bowl very well at this point. This gasket was taken from my other carb that has a slightly different shaped bowl. This was discussed in the following thread http://www.fordbarn.com/forum/showthread.php?t=138395 post 11.



Photo 2 – Lower portion of carb with gasket removed. Red line represents fuel level in bowl.

14 – Nozzle
B – Passage normally covered with gasket

Now we will start following the fuel flow starting at the bowl drain plug.



Photo 3 – View into Drain Plug showing Power Jet (Main Jet).

Now I will remove the nozzle.



Photo 4 – Nozzle with Power Fuel Feed components identified. Red line represents fuel level in bowl. Green wire represents fuel flow.

14 – Nozzle
15 – Nozzle Air Bleeds
20 – Power Jet

This is the only fuel passage for the Power Fuel Feed System but there is an air passage to look at.



Photo 5 – Air passage into Accelerating Well.

The green and copper wires were inserted into the air passage through the location where the lead plug, “A” in Photo 1, was removed.



Photo 6 – Looking into the passage that is normally covered with the gasket.

The copper wire can be seen just above the green wire.

To clean this air passage there is no reason to remove the lead plug. The person that initially tried to remove this plug went straight down with a drill instead of the direction of the plug. This made it very difficult to even see the plug.



Photo 7 – damage at location of Lead Plug.

A – Correct Passage
B – Damage from incorrect removal of plug



Photo 8 - Diagram from Service Manual



Photo 9 – Schematic of Power Fuel Feed System

For an explanation of the Power Fuel Feed System refer to the TSX Service Manual page 4.

As far as references in the patent, the explanation for the Power Fuel Feed starts on page 3 line 98, this is quite long. Page 5 claim 5 onwards refers to the Power Fuel Feed System.

Just for fun lets compare different types of Power Fuel Feed Systems, in their simplest forms, from idle rapidly opening the throttle valve. The following is just my opinion.

A – “Simple” carb: These have a power jet that is adjustable.

1) Throttle opens
2) Air flow increases into venturi
3) Surface tension of gas is broken
4) Gas is drawn out of nozzle

The time it takes to break the surface tension of the gas causes a lean condition and possibly engine hesitation.

B – “Modern” carb: These have a fixed or adjustable power jet and an accelerator pump mechanically connected to the throttle valve.

1) Throttle opens
2) The accelerator pump forces extra fuel into the venture as the air flow increases into the venturi
3) Surface tension of gas is broken
4) Gas is drawn out of nozzle

The action of the accelerator pump compensates for the lean condition experienced in the “simple” carb and reduces hesitation.

C – Electronic fuel injection (in it’s simplest form): consists of; Mass Airflow Sensor (MAS), fuel injector, oxygen sensor and computer.

1) Throttle opens
2) Airflow increases and is measured by the MAS
3) Computer calculates how long to open fuel injector
4) Injector open for calculated time

The sequence could stop here and the engine would operate but:

5) Oxygen sensor measures exhaust for a rich/lean condition
6) Computer recalculates how long to open fuel injector

The only hesitation in the system is the length of time for sensor reading, computing time and operation of injector. All of these are very small.

D – Marvel carb: These have a fixed or adjustable power jet, pitot tube, idle well and accelerating well.

1) Throttle opens
2) Airflow increases into venturi and pitot tube
3) Air pressure in pitot tube increases and applies pressure at the top of the fuel in the accelerating and idle wells forcing the fuel level higher and possibly out of the nozzle.
4) Surface tension of gas is broken
5) Gas is drawn out of nozzle

The action of the pitot tube performs a function similar to the accelerator pump in the “modern” carb. The pressure applied by the pitot tube to the fuel in the wells is controlled by the airflow entering the carb or the mass flow (as in the electronic fuel injection).

On page 1 line 38 of the patent is the objective of the carb (please read this paragraph) and an accelerator pump has been designed with no moving parts.

I thought there would be one more system to look at, called Back Suction Economizer System, but this is not implemented in this carb as the float chamber is vented to atmosphere. I can’t find any more passages to probe so that’s it for the dissection. I will do one more post to look a little closer at the gas adjusting valve and it’s seal.

All for now
Jeff

[duke36]

Great post, thanks for the clarity; just took apart my MARVEL a few days ago and cleaned , etc. due to an unknown leak .All components Ok except mixture screw which was worn, but with some dressing of the tip works fine. The GAV cutaway shows a leather seal below the spring. I purchased the gasket and seals from David @Renners. His GAV seal is rubber, which was missing, and stopped the leak. However the GAV is hard to turn but may loosen up in time. Setting the float parallel to the mating edge was done with a thicker fiber washer that wasn't compressed from age, and it did the job.

[1930artdeco]

Jeff thanks for the info. I just bought an old see one and will restore it this winter with you help. One question though, my choke plate arm is loose and bent. Is there a way to fix it up w/o having to unweld and reweld it? Or is there replacement for it? So far mine looks to be just old and unmolested-woohoo!!! I am sure I will have more questions later.

Mike

[1930artdeco]

Sponsored Links (Register now to hide all advertisements)

Also, the throttle shaft in mine moves a tad, what is the best way to seal it back up? I have heard silver solder and then turn down will work.

Thanks again,

Mike

[TinCup]

Is the idle jet removable?

[juke joint johnny]

Excellent Thread very informative

I have one of these carbs on a Fordor I recently bought, When I pull the choke out gas pours out of it , Scary!! took it off quick !!!
should be able to sort it now I've seen this thread

Performance wise!!

How do people find the Marvel compares to the Tillotsen or the original Zenith?

[1930artdeco]

I believe the idle jet 'stick' is pressed in, I could be wrong though. I find it better performance wise than the Zenith but I think it is worse on MPG. But I can cruise at 50 MPH easily now.

Mike

[Henry's Lady's Man]

Here's what I can add... hope it helps.

file:///Users/mac/Documents/AUTOMOBILES/SPECIFIC%20VEHICLES/MODEL%20A%20FORD/MODEL%20A%20-%20MAINTENANCE%20&%20REPAIR/MAINTENANCE%20-%20ITEMIZED/C%20-%20D/CARBURETORS/Carburetor%20Types/MARVEL-SCHEBLER/Marvel%20Carburetor%20Disection%20-%20The%20Ford%20Barn.webarchive

[Henry's Lady's Man]

A manual for the MS

Marvel Schebler Manual-DLTX-TSX

[Henry's Lady's Man]

FORM NO ME 184
for
MARVEL-SCHEBLER
TRACTOR and INDUSTRIAL CARBURETERS
MODELS DLTX & TSX
MARVEL-SCHEBLER PRODUCTS DIV. BORG-WARNER CORPORATION DECATUR, ILL., U S.A.

Marvel-Schebler Products Division, Borg -Warner Corporation, Decatur, Illinois, U. S. A.
Marvel-Schebler Carbureters are used on thousands of tractor and industrial engines and have been designed to provide many years of trouble-free service, however, as in the case of all mechanical devices, they do in time require ;,roper service and repairs. An understanding of their construction and how they operate as well as an understanding of their function with respect to the engine will not only avoid many false leads on the part of the service man in diag- nosing so-called carbureter complaints but will create customer satisfaction and a profitable business for the progressive service shop.
To understand a carbureter it is necessary to realize that there is only one thing that a carbur- eter is designed to do and that is to mix fuel and air in the proper proportion so that the mixture will burn efficiently in an engine. It is the func- tion of the engine to convert this mixture into power.
There are three major factors in an engine which control the change of fuel and air into p o w e r : 1-Compression. 2-Ignition. 3-Car- buretion.
Carburetion has been listed last because it is absolutely necessary for the engine to have good compression and good ignition before it can have
good carburetion.
When the average person thinks of "carbure- tion" they immediately think of the carbureter as a unit. Carburetion is the combined function of the carbureter, manifold, valves, piston and rings, combustion chamber, and cam shaft.
It can be readily seen that "carburetion" is a far deeper subject than consideration of the car- bureter alone, and expecting the carhureter to cure faulty ignition, compression, valves, etc. will only result in wasted time and effort on the part of the service man and added expense to the customer.
It must be remembered that the function of the carbureter does not extend beyond deliver- ~ n pthe proper mixture of fuel and air to the manifold and the other factors which effect
power and economy cannot be changed or cor- rected by the carbureter. Inability to understand all the factors that effect engine operation is the reason many service mechanics change from fac- tory standards and attempt to improve on the engine set-up by their own methods or "stand- ards". All that any service mechanic should ever try to do is to make the particular engine he is working on as good as the manufacturer in- tended it to be, but he can make it a lot worse. Far too many engines are running below their standard of performance in service today.
For the carbureter to accomplish its function it must be able to vary the mixture strength de- pendent upon the engine demands. It must supply a mixture strength that urill allow the en- gine to give maximum horsepower, whenever the throttle is fully opened, while at part throttle conditions it must lean out the mixture so that maximum economy can be obtained. In addition it must have flexibility throughout the entire range of operating speeds, from idle and part throttle to full power wide open throttle posi- tion. The carbureter must also have an acceler- ating "well" with enough fuel capacity to start handling sudden maximum loads. In other words the carbureter not only varies the volume of fuel andairthatenterstheenginebutalsovariesthe amount of fuel that goes in with a given amount of air, h order to produce the proper mixture proportion for any condition under which the engine is operating a t any time.
In order to understand the function and opera- tion of the Marvel-Schebler Tractor and Indus- trial Carbureters it is well to consider the systems that make up each carbureter. These systems are: The Float System, The Idle System, The Power Fuel Feed System, The Back Suction Economizer System, and The Choke System.
A thorough knowledge of each system will help the service mechanic to quickly locate and correct legitimate carbureter complaints as well as to inspect, repair, and put back to standard any carbureter that requires an overhaul.
Principle of Operation
Marvel-Schebler Products Division, Borg-W arner Corporation, Decatur, Illinois, U. S. A. Float System
FUEL BOWL-!
The float system controls the level and supply of gasoline in the fuel bowl throughout the oper- ating range of the engine.
When the fuel bowl (1) is empty the float and lever (2) and float valve (3) drop and fuel under pressure from the fuel pump (or gravity feed) is forced through the float valve seat (4) around the float valve (3) and into the fuel bowl (1).As the fuel in the bowl approaches the correct operating level it raises the float and lever (2) with enough force to raise the float valve and cut off the flow of fuel into the bowl.
As fuel feeds through the carbureter jets into the engine the fuel level (5) drops, allowing additional fuel to enter the fuel bowl.
Under actual operating conditions the fuel level (5) and float and lever (2) automatically position themselves so that the inward flow of gasoline to the carbureter is equal to the out- ward flow of gasoline to the engine.
As can readilv be seen the float system under
the most favorable of operating conditions is subjected to a certain amount of wear. Under
severe conditions or conditions that result in ex- cessive vibrations being transmitted to the carbu- reter, float valve and float valve seat wear is accelerated.
FLOAT VALVE
FLOAT VALVE-3
It should be an estab- lished policy t h a t when- ever the carbureter is dis- assembled for whatever cause the service man make following checks:
1. Examine float valve for any signs of wear. If it is not absolutely true or is grooved and hasn't a perfect taper, a new float valve and also a new float valve seat must be used. These float valves and seats
are supplied in match- ed sets and are tested a t the factory for leaks. Always use a new float valve seat gasket to make sure of a perfect seal.
2. Examine float for any signs of failure. To test metal float submerge float in pan of hot water and if air bubbles are observed replace with new float.
Examine cork float for bare places or cracks in coating. If either are found, or if float shows evidence of having been soggy, replace with new one. (Do not attempt to recover float with shellac or varnish.)
3. Set float height to the proper specification for the particular model carbureter being serviced. Make certain that the entire assembly works free and that there is no binding.
4. Wash fuel strainer assembly in gasoline and clean screen with air under pressure. If the screen, or the threads on the strainer are not in good condition, install a new assembly. When re-installing fuel strainer assembly always use a new strainer gasket if a gasket is used to obtain a seal.
It has been proven, with few exceptions, that with a float system in good order, carbureter flooding only occurs when dirt or foreign matter becomes lodged between the floatvalve (3) and float valve seat (4).
Marvel-khebler Products Division, Borg-Warner Corporation, Decatur, Illinois, U.S.A. The Idle System
SECONDARY IDLE ORIFICE-8
IDLE ADJUSTING NEEDLE SEAT-I2
PRIMARY IDLE ORIFICE-7
IDLE NEEDLE-13
FUEL BOWL CHAMBER-9
The idle system controls the Aow of fuel a t idle speed and at slow speeds until the throttle is opened wide enough to allow the power fuel feed system to function.
When the throttle valve (6) is in the idle posi- tion the edge of the valve is between the primary idle orifice (7) and the idle orifice
(8). With the valve in this position the air pres- sure (manifold vacuum) at the primary idle orifice (7) is lower than the air pressure in the fuel bowl chamber (9) and fuel is forced from the fuel bowl (1)into the idle fuel passage (10). As the fuel travels through the idle fuel passage (10) it passes through the metering orifice of theidlejet (11)tothepointwhereitiscombined with air entering through the idle adjusting needle seat (12). The mixing of air with gasoline helps to atomize the fuel and this Process is repeated at the secondary idle orifice (8) as the fuel travels through the idle fuel passage (10). As this rich mixture of fuel and air ernergesfrom the primary idle orifice (7) it is reduced to car- uect proportions by the air which passes around
the throttle valve (6) since this valve must be slightly open to permit the engine to idle. The resultant mix- ture is correct for operat- ing engine a t idle speed, provided the idle adjust- ing needle (13) is prop-
erly adjusted.
As the throttle valve (6)
is slowly opened from the slow idle position it gradu- ally subjects the second- ary idle orifice (8) to in- take manifold vacuum, and the secondary idle orifice (8) no longer bleeds air to the idle fuel passage (10) but feeds a n addi- tional quantity of fuel into
the engine. This is proper since the throttle valve is now open wider and will admit a greater amount of air to blend with this additional fuel to maintain the correct proportions of fuel and air for the engine.
As the throttle valve (6) is opened still wider, the idle fuel delivery begins to fade out, how- cver,thethrottlevalve atthispoint isfarenough open for the power fuel feed system to begin functioning.
The idle system as described above is the most positive and satisfactory of idle systems, as it is working under very high suction and the mixture flows through the small passages and orifices at very high velocities. It is necessary to bear in mind, however, that there are times these small holes may plugged \vith particles of dirt or foreign matterand will clean. ing. At such times the passages, jets, and small drilled holes should only be cleaned with a cleaning fluid such as gasoline and air under pressure. Never use drills or wires as a change in size of these small openings will change the entire calibration of the carbureter.
Page 3
Marvel-Schebler Products Division, Borg-Warner Corporation, Decatur, Illinois, U.S. A.
POWER JET-20
POWER ADJUSTING NEEDLE-18
With the throttle valve (6) in slow or just off slow idle position, fuel rises up through the nozzle (14) and out the nozzle air bleeds (15) to fill the accelerating well (16) to approxi- mately the height of the fuel level in the fuel bowl (1).
As the engine speed is increased from the slow idle position the air flowthrough the venturi (17) is gradually increased, and, as the idle
system begins to diminish,the velocity through the venturi (17) is high enough to create a pres- sure at the tip of the nozzle (14) slightly less than the pressure in the fuel howl chamber (9) and the accelerating well (16). Fuel, therefore, feeds from the fuel bowl (1) through the open- ing between the power (load) adjusting needle
(18) and the power adjusting needle seat (19), through the power jet (20) and out the nozzle (14) to be discharged into the air stream at the
venturi (17). At the same time, the fuel that is stored in the accelerating well (16) is also forced through the nozzle air bleeds (15) into the nozzle (14). But, because the size of the power jet (20) and the position of the power ad- justing needle (18) restrict the amount of fuel which can enter the nozzle (14), the fuel in the accelerat- ing well (16) will soon be exhausted and air will then enter through the nozzle air bleeds (15) to mix with the fuel passing through the nozzle (14). The amount of air that can enter into the nozzle (14) is limitcd by the size of the nozzle air vent (21).
The result of air bleed- ing into the nozzle (14) is, to help atomize or break ua the fuel into finer par- ticles,to regulate the quan- tity and the rate of dis-
charge of the fuel fed from the accelerating well (IF), during acceleration, and to inovide the correct mixture proportions for full throttle operation.
As the throttle valve is opened toward the wide open position the velocity through the ren- turi (17) continues to increase, lowering the air Pressure at the nozzle (14) and resulting in additional fuel being supplied to the engine as the speed is increased.
When the throttle valve (6) is opened sud- denly from slow or just off slow idle position, the fuel stored in the accelerating well (16) is forced out through the nozzle air bleeds (15) very rapidly and serves to provide the extra richness required by the engine to meet the sudden load. When the throttle valve (6) is closed fuel again fillsthe accelerating well (16), ready for the next acceleration.
Parre 4
Power Fuel Feed System
THROTTLE VALVE-6
NOZZLE AIR VENT-21
FUEL BOWL CHAMBER-9
Marvel-Schebler Products Division, Borg -Warner Corporation, Decatur, Illinois, U.S.A. Back Suction Economizer System
The amount of fuel supplied to an engine is
controlled by the size of the power jet, the
sition of the power adjusting needle, and the
difference in air pressure between the fuel bowl
chamber and the veuturi. However, in many
engines the mixture must be leaned out
tionally during part throttle operation to obtain maximum economy. T~ provide this leaner
mixture Marvel-Schebler Tractor and Industrial Carhureters make use of the "Back Suction Economizer System, With this method of meter- ing fuel, the air pressure in the fuel bowl chamber is regulated and controlled according
to load conditions by a combination of bowl vent and economizer passages communicating
with the bore the carbureter. Through regulations of the air pressure in the
fuel bow' chamber the the carbureter can be controlled to provide the prop- er mixture proportions for the engine.
All the air that enters the fuel bowl chamber (I)) must first pass through the air cleaner and the howl vent (22). The size of the bowl vent (22) controls or limits the amount of air that can enter the fuel bowl chamber (9). The
ECONOMIZER ORIFICE-24
ECONOMIZER JET-23
FUEL BOWL CHAMBER-9
amount of air that is drawn out of the fuel bowl chamber (9) is controlled by the size of the economizer jet (231, the economizer orifice (24) and the position of the throttle valve (6) as its position determines the manifold vacuum or suction on the econo- mizer orifice (24). As the throttle valve (6) is opened from the fast idle position the economizer orifice (24) is gradually ex- posed to manifold suction, and air flows from the fuel bowl chamber (I)),through the economizer jet (23) and out the econo- mizer orifice (24). This air must be re- placed by air entering through the bowl vent (22) but as the size of the bowl vent (22) restricts the amount of air that can enter, the resultant pressure in the fuel bowl chamber (9) will be lowered, reduc- ing the difference in air pressure between the nozzle (14) and the fuel bowl chamber (9). The flow of fuel will therefore be re- tarded so that the exact economy mixture ratio will be delivered to the engine at this particular throttle opening. Opening the throttle valve (6)further exposes the entire economizer orifice (24) to manifold suction, resulting in additional air being removed
from the fuel bowl chamber (g), again leaning out the mixture ratio to the correct proportions
for this new throttle position. After the econo- mizer orifice (24) is fully exposed to manifold suction the amount of air that is drawn out of the fuel bowl chamber (9) is controlled by the manifold vacuum or suction a t any given throttle valve (6) position and as this suction decreases as the throttle approaches wide open position, less air is drawn out of the fuel bowl chamber and additional fuel flows to the engine to provide the extra richness required for operation at
heavy loads where maximum horsepower is necessary.
The "'Back Suction Economizer System" as- sures the proper metering of fuel to the engine throughout the service life of the carbureter as there are no moving parts to wear out or adjust- ments to get out of order. ~t is essential, how. ever, that the system remain free of dirt and foreign matter because any foreign substance in the system will restrict the flow of air thereby creating improper pressures in the fuel bowl chamber and resulting improper fuel delivery to the engine.
Page 5
Marvel-Schebler Products Division, Borg-Warner Corporation, Decatur, Illinois, U.S.A. Choke System
The choke system is used during cold starting and the warm-up period. Under these cold con- ditions it is necessary to supply an additional rich mixture of fuel and air, as only the "light ends" or more volatile portions of the fuel will vaporize with the manifold and air ternpera- tures at these cold conditions. Consequently it is necessary that a large quantity of fuel be available so that there will be enough "light ends," to combine with the air to form a com- bustible mixture for starting the engine.
The function of the choke valve (25) is to restrict the amount of air that can enter the car- bureter and to increase the suction on the nozzle
(14) so that additional fuel will be drawn into the manifold. As soon as the engine fires and runs the rich mixture must be rapidly reduced to prevent stalling. This change in mixture is ac- complished by the operator positioning the choke valve to provide the proper mixture. However, a few degrees movement of the choke valve (25) will make a big change in the mixture strength
and to help reduce the sensitivity of the choke
valve (25) position use is made of a spring loaded relief valve (26) in many applications. This valve opens automatically with engine speed and load and eliminates a great deal of manipulation of the choke on the part of the operator.
When the engine has obtained normal oper- ating temperature the choke valve (25) must be fully opened to assure maximum power and economy. In addition, extended use of the choke results in more gasoline being supplied to the engine than can be burned. A large percentage of the unburned gasoline is lost through the ex- haust system. The remainder of the raw gasoline is forced between the pistons and cylinder walls, washing away the protective oil film and increas- ing engine wear, and enters the crankcase where it dilutes the engine oil.
Any adjustments that are necessary on the earbureter should never be attempted until the engine has obtained its normal operating tem- perature and the choke valve (25) has been placed in the wide open position.
Page 6
Marvel-Scbebler Products Division, Borg-Warner Corporation, Decatur, Illinois,-U.S.A. Model TSX Carbureter
IDLE ADJUSTING NEEDLE !AIR'
POWER JET BOWL DRAIN
Fis. I-Idle
ADJUSTING NEEDLE
and Power Foe1 Feed Systems
The Marvel-Schebler Model TSX Carbureter is manufactured in three S A E. nominal sizes: 74, inch, 1 inch, and 11%inch. In addition to these vari- ations in size, there are also variations necessitated by the specific require- ment of the engines on which the car- bureters are used. Many engines, for instance, require special throttle and choke operating levers, and for pur- pose of calibration, they may have dif- ferent size jets, nozzles, venturii, etc. For this reason when ordering parts, refer to the individual carbureter serv- ice parts list for the engine on which the carbureter is installed.
The Model TSX Carburetcr consists of only two major castings:
1. The throttle body casting which forms the cover for the fuel bowl. 2. The fuel bowl casting which con-
tains the air inlet.
Cast iron material is used for rug- gedness. It will be noticed (Figure 1) that all passages, whenever possible, are drilled from the top face of the fuel bowl casting to prevent any fuel leaks to the outside of the carbureter, because uf shrunken gaskets or defec-
in^ tests to vrovide the exact fuel requirements for maximum economy at part throttle opera-
tion. Always use the economizer jet specified in the individual carbureter service parts list to assure proper engine operation. On some carhu-
IDLE ADJUSTING NEEDLE 'FUEL'
tive hole plugs, and also to prevent vapor lock or "percolation" of the fuel when the carbureter is operated under ex- tremely hot conditions, resulting in hard start- iqg or erratic engine op- eration.
The Model TSX carbu- reter is completely seal- ed against dust or dirt. All air entering the fuel bowl of the carbureter must first pass through the air cleaner. The throttle shaft bearings
and choke shaft bear- ings are sealed to elimi- nate dust and dirt enter- ing at these points.
The back suction econ- omizer system (Figure 2 ) is provided with a removable economizer jet. The size of this jet has been carefullv es- tablished by engheer-
ECONOMIZER
Fix. 2-Back
Suetien Economizer System
VOMIZER JET
Page 7
Marvel-Schebler Products Division, Borg-Warner Corpuration, Decatur, Illinois, U. S. A. Model TSX Carbureter
CHOKE VALVE
GASOLINE DRAIN STRAINER
Fig. 3-Float
and Choke Systems
air adjusting idle needle. The upper inset in Figure 1shows an idle adjust- ing needle which alters the amount of fuel and air mixture which enters the carbureter bore from the idle passage. This is commonly known as a fuel ad- justing idle needle. It is important to ren1ernbt.r in setting the idle mixture the air adjusting idle needle must be turned in, or clockwise, to enrich the idle mixture, and the fuel adjusting idle needle must be turned out, or counter-clockwise to enrich the idle mixture.
A dual float mechanism (Figure 3) is used in a fuel bowl that almost com- pletely surrounds the nozzle. This de- sign and construction is such that the tractor, or engine, can be operated at any angle up to 45 degrees without seriously affecting the fuel and air ratio and without flooding because the mean level a t the nozzle tin is nracti- tally constant at any angle of bpera- tion.
Some carbureters are equipped with a spring- loaded governor control lever to permit manual closing of the throttle to an idle position for engines equipped with certain type governors. An example of this type lever is shown in Figure 4, however, there are other variations of this type dependent upon the particular application.
While there are many variations produced by combining the different types and sizes into a specific application, all Model TSX carbureters incorporate the same engineering principles and are alike from a functional standpoint.
reter models the proper fuel requirements are established without the use of an economizer jet and the fixed economizer orifice machined in the carbureter throttle body regulates the fuel sup- plied to the engine. In addition, there are engine and carbureter combinations that do not require the back suction economizer system. In these carbureters the economizer orifice has not been machined in the throttle body casting.
To provide additional economy, in addition to the back suction economizer system, some carbu- reters are provided with two adjusting needles, the low speed or idle adjusting needle, and the power or load adjusting needle. However, the power adjusting needle is not always required and for applications of this nature the fixed jet type carbureter is used in which the power jet controls the amount of fuel that is supplied to the engine.
There are two variations in carbureters hav- ing the power adjusting needle,commonly called the adjustable jet type carbureter. In Figure 1 is shown these two arrangements. The adjust- ment of either type is accomplished in the same manner.
A large percentage of the Model TSX Carbu- reters are l~rovidedwith an idle adjusting needle which alters the fuel and air proportions of the mixture which enters ;llz carbureter bore from the idle passage (Figure 1).This is known as an
Fig. 4-Spring-Loaded
Governor Lever
Marvel-Schebler Products Division, Borg-W arner Corporation, Decatur, Illinois, U. S. A.
Service Instructions for Model TSX Carbureters
Type A-Fixed Jet
Type B-Adjustable Jet
Type C-Adjustable Jet
The following procedure for service of all Model TSX Carbureters is for a complete overhaul. After removing carbureter from engine wash thoroughly with cleaning fluid such as gasoline to permit examination of external parts for damage. For type carbureter being serviced see illustrations above. Instructions apply to all types unless specified otherwise.
Remove Power Adjusting Needle A..tmbly.
Type B.
2-
Remove Bowl Cover Screws and Loek Washer.
Separate Castings.
3-
Remove Float Valve, Bowl Casket, and Venturi.
If Valve is grooved or damaged, replace Valve and Float Valw Seat.
4-
Remove Float Valve Seat and Caeket.
Remove Economizer Jet.
TOTE.Sot reuulwrl in ;,I1 carbureters. Check service parts list or repair kit of carbureter being serviced.
6-
Remose Idle Jet
NOTE.Not required in all carbureters. Cheek service parts list or repair kit of carbureter being serviced.
7-
Removins Idle Adjusting Needle and Spring
Replace with new Needle if grooved or damaged
Remove Throttle Valve Screws. Valve, and Throttle Shaft and Lever Assembly
Replace with new shaft 1 and lever assembly if ex- cessive looseness between shaft and throttle body.
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Marvel-Schebler Products Division, Borg-W arner Corporation, Decatur, Illinois, U. S. A. 14-
Remove Throttle Shaft Packing Retainer
and Packing
Force out Retainer with small screwdriver or punch
10-
Remove Main Nozzle and Gasket.
Type A Type B
11-
Remove Power Jet.
12-
Remove Power Adjusting Needle As.cmhly.
Type C
Carbureters not having. adjustable needle remove power jet.
Remove Main Nozzle and Gasket.
Type C
Remove Retainer Plug and Gasoline Drain Strainer.
Strainer can only be re- placed an earbureters hav- ing a curled hair or felt type strainer. Only re- place when impassible to clean with gasoline and compressed air. Porous metal type strainer can- not be replaced. Clean only.
15-
Remove Choke Valve Screws. Valve, Choke Shaft & Lever Assembly, Choke Return Spring, and Choke Bracket.
16-
Remove Choke Shaft Packing Retrine.
and Packing.
Force out retainer with small serewdriver
or punch.
"ASSEMBLE
17-
In.t.11 Throttle Shaft Packing and Retainer.
Assemble new retainer and packing on throtpe shaft. Insert shaft in carbureter and tap lightly until retainer is flush with casting face.
16
Install Throttle Valse and. Screw*.
Install valve with angle identification mark facing. flange face of carbureter. Tap valve lightly to ten- ter in throttle bore. Tight- en screws securely.
"Before assembling carbureter, clean castings, channels, and parts with carbureter cleaning fluid and air under pressure. Make certain all small holes and channels are open and free from carbon and dirt. Do not use wire or small drills to clean out small holes as a slight change in size of these holes will affect the carbureter operation. T o assure a successful overhaul always replace all worn or damaged parts and any parts that are questionable. Always use all new gaskets.
i
. A:...,
On carhureters counter-
bored ?&" to &" deep in-
stall retainer wlth CUD
facing towards eastmi. Taplightlyunt~fllushwith I=. casting face.
Marvel-Schebler Products Division, Borg-Warner Corporation, Decatur, Illinois, U. S. A.
19- 25-
Install Economizer Jet.
Install Idle Jet.
21-
1n.tall Idle Adjusting Needle and Spring.
Set an.n.roximatelv one turn from seat for preliminam setting.
22-
Install Float Valve Seat and Gasket.
Use new Float Valve and Seat Assembly.
13-
Assemble Bowl Cover Gasket and Ventvri
in Casting.
Install float valve.
Install Float and Lever Assembly and
Float Lever Pin.
Set floats %" from gasket face to nearest edge of float, keeping edge of float parallel with gasket. Ad- just by using bending tool #M-8.
1n.tall Choke Shaft Packinn Retainer and f
-
1
Packing. I
Install retainer as shown in illustrations below. Note: On some carbureter models the packing is re- tained by choke bracket in place of packing retainer.
, .,*'
On carbuleters counter- I
bored &" to %" deen ~ n stall retainer withLcur, facing away from castink. Tap lightly until flush with casting face.
26-
Install Choke Bracket, Choke Return Spring. Choke Shaft and Lever A*sembly, Valve. and Screws.
Center valve in casting before tiehtening screws.
Install Power Jet. Type A
Type B
Install Main Nozzle and Gasket.
Type A
Type B
Use new gasket.
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Marvel-Schebler Products Division, Borg-Warner Corporation, Decatur, Illinois, U. S. A.
PRELIMINARY ADJUSTMENTS
Set throttle stop screw so that throttle valve is open sliahtly. Make certain that fuel supply to earhureter is
open. Close choke valve. Start engine and partially release choke. After the engine has been run sufficiently to bring up to operating temperature throughout, see that choke is returned to wide open position.
LOW SPEED OR IDLE ADJUSTMENT
Set throttle or governor control lever in slow idle position and adjust throttle stop screw for the correct engine idle speed. (On a new, stiff engine this speed must be slightly higher than required for a thoroughly run-in engine.) Turn idle adjusting needle* until en*ne begins to falter or roll from richness, then turn needle in the opposite direction until the engine runs smoothly.
SOTE: It is better that this adjustment he slightly too rich than too lean.
'IDLE ADJUSTING NEEDLE-AIR
ADJUSTING
P a g e I2
29-
Install Main Nozzle and Gasket.
Type C
Use new gasket.
Assemble Castings.
Invert throttle body and lower fuel howl over floats taking $recaution that ventnri guides bodies into position.
30- 33-
Install Power Adjusting Needle Assembly.
Type C
Use new gasket.
Set approximately one turn from seat for preliminary setting.
31-
Install Gasoline Drain Strainer & Retainer Plug.
Stake retainer plug in place with center punch to insure secure locking.
Install Bowl Cover Screw. and Lock Washers.
Tighten screws madually until all are tight.
Install Power Adjusting Needle Assembly.
Type A
Set approximately one turn from seat for preliminary setting.
Adjustment Instructions
NOTE: Carbureters TSX-107. TSX-330, TSX-339, TSX-355, TSX-385 and TSX-398 are the fuel od. jurring l y ~ eidle needle. AN orher Model TSX Corburererr use the oir odjurting type idle eerdle.
To richen the idle mixture turn the idle adjusting needle to the right or clockwise.
';IDLE ADJUSTING NEEDLE-FUEL
ADJUSTING
To richen the idle mixture turn the idle adjusting needle to the left or counter-clockwise.
POWER OR LOAD ADJUSTMENT (TYPE B, TYPE C)
With the engine running a t governed speed under load, turn power adjusting needle to the right, or clockwise, a little st a time until the power drops appreciably. Then turn the needle to the left, or counter-clockwise, until the engine picks up power and runs smoothly. This will give an economical part throttle mixture, and, due to the eeonomizel. action, the proper power mixture for full throttle operation. Due to variations in temperature or fuels it may be necessary to richen up this mixture by backing out the power adjusting needle, a small amount at a time until good acceleration is obtained.
Mawel-Schebler Products Division, Borg-Warner Corporation, Decatur, Illinois, U.S. A. Model DLTX Carbureter
THROTTLE BODY
FUEL STRAINER ASSfMBLY
SEDIMENT CUP DRAIN PLUG
FLOAT VALVE SEAT
FLOAT VALVE
FUEL BOWL
NOZZLE RETAINING SPRING
The MarvelSchebler Model DLTX Carbureter is a horizontal type carbureter used on John Deere tractors. To meet the specific engine re- quirements of the individual tractor on which the carbureter is installed requires different size jets, nozzles, venturi, throttle and choke oper- ating levers, etc. For this reason, when ordering
parts, always refer to the individual carbureter serlice parts list for the engine on which the carbureter is installed.
The Model DLTX Carbureter consists of two castings :
1. The throttle body casting which contains the air inlet.
2. The fuel bowl casting.
The throttle body casting contains, in addition to the throttle assembly, a venturi machined in the casting and the choke assembly. Cast iron material is used f o r ruggedness. All passages, nhenever possible, are drilled within the cast-
ing to prevent any fuel leaks to the outside of the carbureter because of shrunken gaskets or defective hole plugs.
The Model DLTX Carbureter is completely sealed against dust or dirt. All air entering the fuel bowl of the carbureter must first pass through the air cleaner. The throttle shaft bear- ings and the choke shaft bearings are sealed to eliminate dust and dirt entering at these points. New throttle shaft bushings can be installed when the bearings have become worn.
The float mechanism is contained in a cast iron fuel bowl (Figure 1) on all DLTX models with the exception of Model DLTX-26 and Model DLTX-46. In these two carbrueters the float assembly is retained by the throttle body casting surrounded by a stamped metal fuel bo\isl.
All models have a fuel strainer to prevent dirt and foreign substance from entering the fuel
THROTTLE LEVER STOP SPRING LOAD ADJUSTING NEE
CHOKE VALVE
Fis. I-Choke, Float and Power Fuel Feed Systems
Page 13
Marvel-Schebler Products Division, Borg-Warner Corporation, Decatur, Illinois, U.S. A. Model DLTX Carbureter
BOWL YE
BOWL DRA
BOW1 RE1AlNlNG NUT
PLUG
ECONOMIZER PASSACC
bowl. To service the fuel strainer in the cast iron fuel bowl, first remove the sediment cup drain plug (Figure 1) to permit any dirt to drain off. Then remove the fuel strainer assembly and clean with gasoline and air under pressure. Flush sediment cup by turning on fuel supply valve using a small brush to wash out any re- maining dirt in cup. Be careful not to damage or remove composition gasket on fuel strainer assembly. Always replace any damaged gasket.
A calibrated economizer plug (Figure 2) is used in the back suction economizer system to regulate the air pressure in the fuel bowl cham- ber for proper fuel delivery to the engine. The size of the plug is carefully established by engi- neering tests and the specified size for a given carbureter model must always be used to assure the proper operation of the carhureter on the engine. In some models, a calibrated fixed orifice is machined in the throttle body casting in place of the economizer plug.
To provide additional economy, in addition to the back suction economizer system, the carbu- reter provides for two adjusting needles, the low speed or idle adjusting needle and the load ad- justing needle. These needles must not be inter- changed. The idle adjusting needle head is brass plated and the load needle cadmium plated
(gray color) to distinguish.
A throttle lever stop spring (Figure 1 ) is pro- vided to prevent uneven running or "hunting"
(governor opening and closing) when the load
is released and the governor closes clear shut. Turn the throttle stop screw against the throttle lever stop spring until the "hunting" is corrected
and idling is satisfactory. Normally there is ? i ~ " clearance between the throttle stop screw and
the throttle lever stop spring a t fast idle.
While there are many variations produced by combining the types and sizes into a specific ap- plication, all Model DLTX Carbureters incorpo- rate the same engineering principles and are alike from a functional standpoint.
IDLE ADJUSTING NEEDLE
Fig. 2-Idle
and Back SIretion Economizer Systems
Marvel-Schebler Products Division, Borg-W arner Corporation, Decatur, Illinois, U.S. A. Service Instructions for Model DLTX Carbureters
Type A-Cast Fuel Bowl
The following procedure for service of DLTX carbureter models is for a complete overhaul. After removing carbureter from engine wash thoroughly with cleaning fluid, such as gasoline, to permit examination of external parts for damage. For type carbureter being serviced see illustrations above. Instructions apply to both types unless specified otherwise.
Remove Bowl Retaininq Nut, Gasket, and Nozzle Retaining Spring.
Separate Castings.
Remove Fuel Strainer A*sembly and Gasket.
Replace assembly if screen or threads are not in good
Remove Float and Lever I Assembly & Float Valve.
Type A-
Replace float valve and seat if valve is grooved or worn or seat damaged.
Remove Float V alve, Float Valve Seat & Gasket
Type B-
Replace Float Valve and Seat if valve is grooved or worn or seat damaged.
7-
Remove Load Adjusting Needle.
Replace needle if groaved or damaged.
Remove Idle Adjusting Needle.
Replace needle if grooved or damaged.
Remove
Float
V alve
Seat
Remove seat with Schebler Tool No. 725A.
4-
Remove Float Lever Bear- ing Screw. and Float Lever Pin.
Type A-
Replace screws and pin if parts are worn.
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Page 15
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Page 16
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Marvel-Schebler Products Division, Borg-W arner Corporation, Decatur, Illinois, U.S. A.
Service Instructions for Model DLTX Carbureters 13-
Remove Throttle Valve Screws. Valve, & Throttle Shaft & Lever Assembly.
N0TE:On some models it is necessary to first re- move throttle lever from shaft before throttle valve can be removed. Replace throttle shaft if worn.
16
Remove Choke Valve Screws and Valve.
Do not remove choke shaft
11-
Remove Nozzle.
Insert fiat end of Schebler Tool No.2599 under choke shaft and force nozzle down as far as possible.
11A-
Insert bent end <,f tool over choke shaft and fore? nozzle out.
Remove Choke Shaft and Lever Assembly.
Replace shaft and lever assemhly if shaft is worn.
1ZA-
Remove Choke Shaft and Lever Assembly.
Replace shaft and lever assembly if shaft is worn.
Remove all Channel Plugs.
Throttle Shaft Bushins Repair
Procedure f o r replacing yorn throttle shaft bush- Ings.
Remove Upper Throttle Shaft Bushing.
Insert Schebler Tool No. 2603 & drive bushing out. NOTE: On Models DLTX- 26 and DLTX-46 remove bushinp with tool No. M-130.
Remove Lower Shaft Bushing.
Insert Sehebler Tool No. 2603 through upper throttle shaft bushinzboss and drive bushing out. On Models DL TX-26 a n d DLTX-46 use Tool No. M-131.
Install Lower Shaft Bush- ing---Open End Bushing.
Place new lower bushing on Tool No. M 132 and drive bushing in casting "11 to shoulder on tool.
16A-
Install Throttle Shaft Hole Plug.
Drive plug flush with face of lower throttle shaft bushing boss.
16B-
Install Lower Shafb Bush- ing-Blind End Bushing.
Drive bushinp udtil flush with face of casting boss.
Marvel-Schebler Products Division. Borg-Warner Corporation. Decatur, Illinois, U.S.A. Service Instructions for Model DLTX Carbureters
21A-
* Before assembling carbureter, clean castings, channels, and parts with carbureter cleaning fluid and air under pressure. Make certain all small holes and channels are open and free from carbon and dirt. Do not use wire or small drills to clean out small holes as a slight change in size of these holes will affect the carbureter operation. Gum deposits not removed by carbureter cleaning fluid, clean with a lacquer thinner. To assure a successful overhaul always replace all worn or damaged parts and any parts that are questionable. Always use new gaskets.
Install Choke Assemblv Part., Choke, V alve, and Screws.
Before assembling. dust cap attach the choke flex spring as shown in illus- tration below.
21B-
Attach Choke Flex Spring
With choke valve in open position attach spring to plns on choke lever and shaft as shown.
22-
Install Idle Adjueting Needle.
Set approximately 11h turns from seat for pre- liminary setting.
NOTE: Idle needle brass plated to distinpuish.
23-
Install Load Adjusting Needle.
Set approximately 1 turn from seat for preliminary setting..
NOTE: Load needle ead- mium plated (gray color) to distinguish.
1n.tall Nozzle.
Tap bottom of the nozzle lightly to seat in casting.
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Marvel-ScheblerProductsDivision.Born-WarnerCm~orationD.ecatur.Illinois,U.S.A. ----
Service Instructions for Model DLTX Carbureters 1 Install Float and Lever
- +.
Set float %" on models DLTX-67 to DLTX-73 in- clusive.
I Measure from tov of fuel I bowl to top of float. Use 1Schehler Tool No. 35 to
bend float lever.
ADJUSTMENT INSTRUCTIONS
] Assembly & Float Valve. , .,, TYPE A-
..
: -.' .?
,,,.!:; 'j ~V
Before installing floatsuh-
merge in pan of hot wat- er. Re~laceif air bubbles are observed escaping from float.
Install Float Lever Pin and Float Lever Baaring Screw..
Type A-
Install Float Valve Seat and Casket.
Type A-
Use new gasket. Examine action of float. Be sure there is no sticking be- tween fingers on float lev- er and head of float valve.
Set Float Level.
Set float 5''on models DL TX-3 t o DL TX-63 in-
h.
PRELIMINARY ADJUSTMENTS
Set speed control lever so that throttle valve is open slightly. Make certain that fuel supply to carbureter is open. Close choke valve. Start engine and partially re- lease choke. After engine has been run sufficiently to bring up to operating temperature throughout, see that choke is returned to wide open position.
IDLE ADJUSTMENT
Advance speed control lever to wide open throttle position which will be fast idle or governor controlled idle. Adju?t idle adjusting needle until engine runs evenly.
NOTE: To enrich the idle mixture turn idle adjusting needle to the left o r counter-clockwine.
LOAD ADJUSTMENT
To secure maximum fuel economy with tractor pullinp load turn the load adjustin~needleto the right, or clock- wise, until the power drops appreciably. Then turn the needle to the left, or eounter-clockwise, until the entine picks up power and runs smoothly. Due to variations in temperature or fuels it may he necessary to richen up this mixture by backing out the power adjusting needle, a small amount at a time, until good acceleration is obtained.
If, when load is released, aovernor closes throttle clear shut, causing uneven running or "hunting." (governor on en in^ and closina) turn the throttle stor, screw against the th;ottle level4:<on spring until the "hunting" is cor- rected and idling is batisfactory. Normally there is A'' clearanee between the throttle stop screw and the throttle lever stop spring at fast idle.
".
Mawel-Schebler Products Division, Borg -Warner Corporation, Decatur, Illinois, U. S. A. Service Complaints
IDLE-UNEVEN
The idle construction used in Marvel-Schebler Tractor and Industrial Carbureters is the most positive and satisfactory of idle systems, because it is working under very high suction and the mixtrlre flows through the small passages a t very high \.elocities. It is necessary to bear in mind, however, that there are times when these small holes may become plugged with particles of dirt or lint, but very seldom. If idle trouble is experi- enced, first check the manifold to cylinder head
gasket and the carbureter to manifold gasket for air leaks. At slow idle an engine requires only approximately 20 to 25 lbs. of air per hour, and a slight leak will result in a very erratic or rough idling engine.
Other causes for a ruugh idling engine are: uneven compression, caused by sticky or leaking valves; leaking valve seats; tappets with im-
IN OPERATION
proper clearances; leakage past pistons and rings; cylinder head gasket leaking; weak spark, or spark plug points not spaced correctly; ignition cable covering cracked and thus ground- ing spark, and cable not assembled properly in the distributor cap which causes corrosion and weak spark.
The spark timing of the engine is most im- portant, and should also be checked very care- fully and set exactly on the mark as called for in factory standard specifications. In fact, all of the above items must be checked very care- fully to factory standards, and not just given a casual inspection with the common expression "Everything looks O.K." You can KNOW defi-
nitely that the tractor ia up to the standards set by the manufacturer.
Complaints are received from the field that the engine will not pull or develop its maximum horsepower, or that it develops good power, but uses far too much fuel. Too often a service man will at once change the carbureter to correct these complaints, but by so doing he may not be successful in overcoming the difficulty
It must be clearly understood by all service- men that when a new engine is designed and developed the management first decides what horsepower they want this engine to produce at a definite rated speed. The engineering depart- ment develops the new engine to pull the re- quired horsepower. In the design there are cer- tain fixed dimensions that never change. For instance, the bore and stroke, the displacement, compression ratio, diameter of valves, lift of valves, diameter of intake passage. The carbu- reter engineer works out the diameter of throttle
bore, venturi size, and provides for means of adjusting and regulating the power fuel mixture ratio, as well as the idle. Now, in service, con- sider, that the compression, ignition, and timing have been checked and found to he 100rr: in this engine. If the air intake temperature and the water temperature is held constant, then the only variable we have that affects maximum horsepower is the fuel mixture ratio.
If compression, ignition, and timing, which are variable, are first properly checked by a service man and set to factory specifications, very little difficulty will be experienced in ad- justing the carbureter to give the maximum horsepower and economy.
A great deal has been said regarding the im- portance of engine tune-up and the reasons for service men being exact in their service work on engines. The reasons why a carbureter nlay not
POWER AND ECONOMY-LOW
Page 19
Marvel-Schebler Products Division, Borg-W arner Corporation, Deeatur, Illinois, U. S. A.
function properly when everything else has been checked and set to factory standards will now be covered.
With the present type carbureter construction used on Marvel-Schebler tractor and industrial carbureters, not very much can go wrong with the possible exception that it may foul with dirt. There are only two places that are subject to wear-the throttle shaft and bushings and the float valve and seat. The wear on the throttle shaft and bushings, and resultant air leak there- from results in a lean idle, and to compensate for the air leak more fuel must be turned on for idle. Wear on the float valve and seat results in a high fuel level in the fuel bowl and flooding trouble. Both faults can be easily observed by the service man, and corrected by replacing worn paxts with new ones. The proper function-
ing of the carbureter is obtained by a series of holes drilled to exact size and location, which do not wear or change location in service. It must be realize that if the carbureter worked correctly at first, when passed by the inspectors at the tractor factory, it will always function the same, provided these passages are all free from dirt.
On a carbureter complaint from the field, the only thing a service man can do to the carhu- reter is to disassemble it. BE SURE that the passages are open and free from dirt, that there is no wear on the throttle shaft and bushings, that float valve and seat are O.K., that the float height is correct, and that a good air-tight seal exists around the bowl gasket. If such carbureter service does not correct the complaints, a com- l?lete check of the engine must again be made.
Mawel-Schebler Products Division. Born-Warner Cornoration. Decatur. Illinois. U.S. A.
Marvel-Schebler Carbureter FLOAT SETTINGS
To check the float setting, the casting must be held in an inverted position so that the float lever is in contact with the float valve and the float valve seated.
Factory
Carbureter Model Setting Where to Measure
DLTX-26 and 46................... 53"................ From the bottom of the nozzle boss to the
DLTX-67, 71, 72, 73
fromnearestsurfaceofthefloat.
the bowl gasket to the nearest surface of the float.
All other DLTX (except duals)
(Cork or MetalFloat) ...... 'h"...............From the bowl gasket to the nearest surface
of the flaat.
Duplex DLTX....................... %"............From bowl gasket seat in casting to bottom of
"H"~.................... .. float.
.............B!" toib"......Fromthegaskettothetopofthefloat.
"MA"
(All except MA-4-5) ........s~s''................. From the top of the float to the gasket.
MA-4-5.~....~....~..................... k2''~~.~...... from thetopofthefloattothegasket "N".................................. 18t"........fromthebowlcoverfacetothebottomof
the float.
"NNF".L ............................ 'k"........... o m top of float to flange gasket.
"TCX? ................................ I A ".~........ from upper bowl gasket to bottom of float
"TRX" .................... .........1 % ."..........From the gasket to the bottom of thc float.
"TSX" %", I", 11%'.'............ %".............From the gasket to the nearest surface of the float.
"TSV" ............................... %"................ From the gasket to the nearest surface of the flaat.
"TTX" .................................. Y ......d o the face of the flange to the bottom of the flaat.
"VD".................................. I % ' ' ~ .L.......From the gasket to the end of float farthest from hinge pin.
"VH"4b" .............................. 1/r"......- . ....o m the nozzle boss to the end of the float furthest from hinge pin.
37,' fromthegasketflangefacetothebottomof the float.
NOTE: Changing the float setting from our standard in an effort to improve the operation of the carbureter or in an effort to prevent flooding, will only result in faulty carbureter operation.
..+
SPECIAL SERVICE NOTE How to Give Your Engines Longer Life!
A loose throttle shaft and worn packings will allow coarse, highly abrasive dirt to be pulled into the engine. It has been proved by actual test, that under extreme dust conditions, duch as encountered by off- the-road-equipment, it is possible to wear the cylinder walls down one thousandths of an inch in 50 hours of operation as a result of leakage around a worn throttle shaft.
Make sure on all engine overhaul and tune up jobs that the carbureter is removed, cleaned and all worn parts replaced.
Remember! it's not the air which is drawn into the engine around worn shafts which wears out rings, valves and cylinder walls, it's the dust and dirt in the air.
Dirt Is Engine Enemy No. 1

[26Tguy]

OUTSTANDING Jeff!!!

Thank you very much for taking the time to share your wisdom!

[Mike V. Florida]

Here is the form 183 manual.

http://www.oldcarmanualproject.com/m...S-DLTX-TSX.pdf

[GMCPASO]

Originally Posted by 1930artdeco

I believe the idle jet 'stick' is pressed in, I could be wrong though. I find it better performance wise than the Zenith but I think it is worse on MPG. But I can cruise at 50 MPH easily now.

Mike

I have found this idle jet is threaded into the lower body with a 10-32 thread. It is a thick walled tube so you can get a firm hold on it and it will come out. Don't know how they set the height of them but I would measure them before removing and reset again with some thread locker.

[wmws]

Jeff. In you article about the Marcel carb in picture 12 you reference "The primary idle orifice (7) can be seen and just below is another orifice. This is the secondary idle orifice (8)."
My carb also has those two orifice but it also has another hole to the right of your primary orifice 7 and also above the throttle plate. It is a much bigger hole. My question is what is this hole.
Sorry I don't seem to be able to show a picture.

[Billy 1931 Model A]

Thanks for this wonderful dissection. My A has this carb. Question: is your starting routine any different with this carb? More choke? Less choke? How much GAV? How much throttle at start?

[Herb Concord Ca]

Both my Model A's have Marvel carbs, both require the GAV open 3/4 turn to start after about 15-20 seconds I can start to close them to about 1/4 turn open. Can't close then completely until motor is warm up (I do run thermostats in both A's). To climb hills I open the GAV and notice the increase in power.

[Aretino]

Read this complete thread dating back to 2014. What a great resource for those using the Marvel.

[Billy 1931 Model A]

Does the GAV act the same way in the Marvel Schebler as in the Zenith?
How much do you open it at start, and how much in normal running?

Herb Concord, I think you answered this question - thanks.