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