I give up
 

Our 1930 A will not idle down without quitting. I have plugged the vacuum wiper connection at the manifold & it made no difference. I removed the intake manifold & filed the connection for the carb flatter & installed new carb gaskets at the bowl & mounting flange. I have removed all jets & made sure they were clear. The float level looks correct. With the upper half upside down I measure 1 1/4" to the gasket surface from the solder line & it measures even on sides & front of float. The timing is good. The engine is a touring engine with high compression head & has about 5ooo miles on it. The throttle shaft is free in the housing with no slop. It's been dying at stops lately. It wasn't doing this before. I have always had it idling a bit fast but now it's worse. I just don't know what else to try. The carb was rebuilt by a reputable Model A parts supplier about 4 years ago. It doesn't drip gas when sitting. I do shut the gas off. when done driving it.

Re: I give up
 

Easy answer #1. If he's still around, contact the carburetor rebuilder (or the vendor you bought the rebuild from). Hopefully, they can make suggestions.

If you just bought a new Ford, I'm assuming for the first servicing, you would not call the Chevy dealer.

Not trying to be a wise ass and I mean no disrespect, but a good rule of thumb ............ if the item functioned properly until now and you were pleased with the work done, why not go back to the guy that did the work?

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You said that you removed the intake. But did you remove the exh. and have them both planed? Is either of them cracked? What about gland rings to keep the exh. manifold from sagging?

Just my 2 cents,

Mike

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The manifolds were machined together a number of years ago. No gland rings though. Never had luck getting them to seat well. I'm not convinced the carb is the issue. I can put another carb on & the car runs the same way.

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Have you checked Idle Air adjustment screw(mis-adjusted or too short) or dirt/rust. Next time it dies stop and remove gas line to ensure it is getting fuel and not plugged with rust??

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I don't see any trouble with the air idle adjustment. The threads seem snug. As for the length, I don't know if it's too short or long.

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Just saw another carb installed doing the same thing.! Cast iron fuel filter or glass bowl? Also installing fuel line into carb too far will restrict fuel flow!

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Woodie: You kind of answerd most of the problem in your post #6. 2 different carbs runs same way. Unlikely its the carburetor, could be a valve issue but leaks in and around manifold deserve a good second or third look

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This ought to be a clue that the problem is likely not carburetor. This sounds to me like a vacuum leak, not a fuel starvation (that would tend to be apparent under load, not at idle). Are you sure you're not leaking around the intake manifold? If I was in your shoes that would be the next thing I'd try - pull the intake/exhaust manifold assembly, check for flatness, and install new copper gaskets (I like the two-piece '31 style). Also check for exhaust manifold sag, this can pull the rear of the manifold down and expose both intake and exhaust ports. Your difficulty with gland rings might point to a sagging manifold...

Also, carb to manifold gasket should be the thick copper style. I've had limited success with the pressed ones.

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Run the engine as low as you can where it runs smooth, take a can of starter fluid and give a quick spray where the intake meets the engine. If the RPMs change you've found your culprit.

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The engine was rebuilt as a touring engine 3 years ag. I wouldn't think there are valve issues yet after 5000 miles. I did replace the manifold gaskets a couple of days ago with the copper round gaskets. The exhaust manifold was new maybe 8 years ago & I had the exhaust & intake manifolds trued up at that time. I did not check for a good match of the manifolds this time. Vacuum leaks are associated with the intake only or am I wrong one this?

Re: I give up
 

Do as mentioned in post #10.
Spray starter fluid all around the manifolds when it is running and listen for a change in engine speed.

When installing manifolds I loosen the two bolts that hold the intake manifold to the exhaust manifold and tighten them after the manifolds are tightened to the block. This allows them to float a bit and seat better.
Be sure to tighten the four manifold bolts a time or three after the engine runs through a few heat cycles.

If the carburetor you switched to came off a good running car then the carburetor is not your problem.

Do you have a plastic inline fuel filter installed. They can cause problems.

Does your fuel line run downhill all the way to the carburetor? I've found having a fuel line loop down and then run uphill to the carburetor can cause problems.

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The fuel line is an original style. No rubber hose & no up hill bends. I have a glass sediment bowl & keep it clean. I tried a propane torch unlit around the manifolds & heard no change in speed.

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Just for idea? Gas cap properly vented!

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Gas cap is vented.

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Where does the term 1-1/4" come from? I've never seen that before, anywhere. All I've ever seen is 1" or 15/16". Verify that the fuel level (not the float height) in the float bowl is correct. Measure and set the fuel level 5/8" below the fuel bowl gasket surface using an external sight gauge.

Stalling on stop has a lengthy list of things that can be the cause. Has the idle speed adjustment screw backed out, allowing the throttle plate to close completely?

Re: I give up
 

Propane torch might show a leak with the fan belt off so there is no airflow from the fan.
Starting fluid is much more telling. Never had a problem with it flaming up while testing with it.

Re: I give up
 

I would try adjusting the float valve by using various shim thicknesses. Sometimes a small shim thickness change will improve low speed performance especially when abrutly stopping.
I would also check the distributor rotor runout. It might be in need of new bushings. If runout is significant it can change the point gap which could be most noticeable at low rpm.

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I'll have to check the distributor run out. I was sure I rebuilt it when I had the engine rebuilt.

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I just checked the distributor. There isn't any wobble of the shaft but there is about .018 up & down movement of the shaft. Could this be some of the idle problems?

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Just thought of this one. This happened to me once, I had the glass sediment bowl screwed on to tightly. I don't know how I did it but once I loosened the screw nut about a turn or so fuel started flowing again.

Mike

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I did replace the air idle mixture screw because of slight scouring on the tip. It turned out that the replacement was about 1/8" shorter than the original screw. Didn't solve the problem though. I would like to get a little more fuel in the bowl but I don't see how. When the top half of the carb is held upside down, the solder line on the float looks to be very evenly parallel to the mating surface. If I remove a washer from under the float valve then I have an uneven condition. When I drop the bottom half of the carb & put a ruler inside to measure the gas, it is about 1" below the mating surface of the carb. I know that's too low.
I just tried starting fluid & it killed the engine. I thought it was idling fast enough. I did not hear the engine rev up faster.

Re: I give up
 

I put some new spark plugs in & it runs a bit smoother now but the idle is still too fast. If I slow it down the engine dies.

Re: I give up
 

I know you said everything is fine with the carburetor but to me your symptoms keep pointing to a clogged idle jet or idle circuit.

I see no where in this discussion what kind of carburetor you have. Idle mixture adjustment on a Marvel is opposite that of a Zenith or Tillitson.

Re: I give up
 

The carb is a Zenith. I can see through the idle jet & blow through it. The passages in the idle circuit will let me run a wire through them.

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I just tried starting fluid & it killed the engine. I thought it was idling fast enough. I did not hear the engine rev up faster.[/QUOTE]

If spraying starting fluid made a change to how the engine runs, in your case it killed the engine you have a leak at the manifold that needs to be fixed.

I'm not sure why you are continuing to fuss with the carburetor if you have already switched to a different carburetor and still had the same problems.
Perhaps I'm missing something.

Re: I give up
 

If spraying starting fluid made a change to how the engine runs, in your case it killed the engine you have a leak at the manifold that needs to be fixed.

I'm not sure why you are continuing to fuss with the carburetor if you have already switched to a different carburetor and still had the same problems.
Perhaps I'm missing something.[/QUOTE]
Agree.

Re: I give up
 

o you know anyone else with an A without this issue? If you do, ask if you can swap over the carb for a trial. If the problem goes away, it was the carby, if it stays, then look elsewhere.

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Any success in getting it running well again?

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I have had cars act like this with ignition components like coil or condenser that were failing but not yet dead.

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Woodie, .18 on the distributor is way too much. You should have .03-.05 up and down movement.

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I think you’re off a decimal point - up and down play should be 0.003”, not 0.03”. But I do agree, 0.018” is excessive. Not sure how you do that unless you omit the spacer at the bottom?

Whether it would affect the idle - I’d look more for the bushings being worn or missing, and therefore affecting point gap. With that much vertical play it appears someone has been there, and no telling what’s what. There should be negligible side-to-side wiggle of the shaft.

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I put a different carb on today & was able to stop the car without it quitting. This tells me it is the carb. Upon taking the carb apart again I noticed the end of the idle jet was slightly mashed on the end. I measured it's length to an old original jet & found it to be about .020 longer than the original. When the carb was assembled without the gasket & the idle jet in place, the carb halves would not meet. I was hoping I had the problem solved. The car runs slightly better but now the air mixture screw must be almost seated to get the best or fastest idle. I guess there is still an air leak. The throttle shaft is snug. The threads for the air mixture screw seem tight. The mounting bolts are snug & so is the bolt that holds the carb together.

Re: I give up
 

I went through this same situation a few years back. Carburetor swaps didn't change anything.
I changed the intake and that solved the problem. I bead blasted it and found a Crack at the vacuum port.
Also look at this.....If you have a air maze on, remove it. Check Carburetor for cracks and try 2 Carburetor to manifold gaskets.

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Recheck plug gap..if too wide engine won't idle down smoothly.

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No air maze. Plug gaps are set at.030 as per others suggestions with a high compression head. This last carb swap ran well so I would think that rules out the manifold.

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Have you fixed the leak at the manifold that you found when you sprayed starting fluid around it?

If not you will be always be having problems with how your car runs.

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I don't think there is a manifold problem since the last carb had it running well. I want to figure the original carb problem out now.

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In a previous post you mentioned that the fuel level in the bowl was 1” from the top when you checked it. Did you adjust the float level to address the low level yet? Maybe the problem isn’t too much air from a vacuum leak but not enough fuel from a fuel level or idle jet problem. Does richening the GAV a bit have any effect on the stalling at stops. I notice that mine has much less tendency to drop the rpms at a stop if the GAV is opened 3/8 turn vs 1/4.

Re: I give up
 

Take the carburettor off and look down the throat. There is a small hole on the float chamber side of it right where the throttle plate rests at idle. With the throttle closed, that hole should be half covered by the plate. If it is not, back off the idle stop and the screws holding the plate to the shaft. Holding the throttle arm in the closed position It should not be against the idle stop), tap the plate with the handle of the screwdriver to make sure it is centred properly. Reset the idle stop and the hole should be half covered. I have sometimes filed the plate a little to get that and other times, put a little solder on it, then file to get the desired result.
That is an often overlooked item and often not mentioned in threads like this.