engine stalling

fundytides

fundytides

Well-known member
Returning from a carshow yesterday with my 31. When I stopped on 2 occassions, after driving about 1/2 hour, the engine would die and be hard to start again. Held the gas pedal to the floor and the car started and idled and drove normally. What typically causes this symptom? I have a stock Zenith carb that has been cleaned and adjusted but does have a piece broken out of the venturi where it extends into the upper body. Would this have anything to do with this problem?
 
IF holding the throttle open allows it to restart, that sounds like the engine was flooded with too rich a mixture. I once had a problem that when the engine was warm and I restarted it, it would run ok for a short while, then stumble and stall from lack of fuel. If I tapped the carb bowl it would refill and I'd be ok. Turns out the carb float would stick in a closed position because there was an imperfection in the carb bowl casting where there was a raised bump near the float. As the carb heated up the raised area expanded to the point where it hit the float. I dremeled it smooth and haven't had a problem since. I wonder if maybe your float is sticking in an open position causing it to flood? Check that the float moves freely on its pivot pin, and that there is clearance all around the float.
 
fundytides said:
Returning from a carshow yesterday with my 31. When I stopped on 2 occassions, after driving about 1/2 hour, the engine would die and be hard to start again. Held the gas pedal to the floor and the car started and idled and drove normally. What typically causes this symptom? I have a stock Zenith carb that has been cleaned and adjusted but does have a piece broken out of the venturi where it extends into the upper body. Would this have anything to do with this problem?
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As above, and from your description, it sounds like flooding. Could be float valve sticking open as above post mentioned. Could also be the jets coming loose from vibration or whatever, when hot, allowing gas to rush into the bowl when stopping.
 
Stalling at idling: Things to check are weak spark, or incorrect mix- too weak (runs hot fuel evaporates in carb ) or as Will N Suggest above too rich! Time to check the ignition, mixture (-try fiddling with the GAV , stopping slowly, check fuel level in carb then look at jets if still no joy ) and also check for air leaks at manifold. A small chip or crack on the venturi will not affect the idling - in fact stock As can run surprisingly well without any venturi at all , unless full power demanded ( Been there done that !)
 
Just a hint. Anytime you think your car has stalled from flooding, turn off the fuel, start the car and then turn the fuel back on. This method will prevent additional flooding while trying to start the engine
 
All the above are good comments. Try screwing the idle mixture screw out (counter clockwise) 1/4 turn. The will lean out the idle.

Does the carburetor drip when parked with the fuel on? If so then it is likely that the float valve is not seating correctly. If not then it is not the float valve.
 
You mention that your car has stalled when you came to a stop. This is a nuisance but can be quite common with a Model A. This is what I think is happening:
1. When you slow down and stop at a stop sign, the gas in the bowl moves forward, raising the float, temporarily shutting off the flow of gas.
2. The compensator jet in the back of the bowl is uncovered with gas allowing air to go into the secondary well and on to the cap jet. The gas mixture goes lean.
3. The engine stumbles and sometimes stalls. Hopefully the float valve doesn't get stuck in the seat or the engine does stall.
4. At this point the only flow path for the gas is from the secondary well and into the idle jet. The throttle plate is nearly closed. Since the secondary well is nearly empty from previous running it is a race to have the secondary well refill and feed the idle jet before the engine stalls.

This is a deficiency of the Zenith carb with the float hinge located at the rear of the float.
Ed
 
Thanks for all of the suggestions and info. I'll check the float level and experiment with different mixture settings.
 
Ed in Maine said:
You mention that your car has stalled when you came to a stop. This is a nuisance but can be quite common with a Model A. This is what I think is happening:
1. When you slow down and stop at a stop sign, the gas in the bowl moves forward, raising the float, temporarily shutting off the flow of gas.
2. The compensator jet in the back of the bowl is uncovered with gas allowing air to go into the secondary well and on to the cap jet. The gas mixture goes lean.
3. The engine stumbles and sometimes stalls. Hopefully the float valve doesn't get stuck in the seat or the engine does stall.
4. At this point the only flow path for the gas is from the secondary well and into the idle jet. The throttle plate is nearly closed. Since the secondary well is nearly empty from previous running it is a race to have the secondary well refill and feed the idle jet before the engine stalls.

This is a deficiency of the Zenith carb with the float hinge located at the rear of the float.
Ed
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I disagree. In fact, I can slam n the brakes of any of my Model A's and not stall. Engine idle speeds are less than 400 RPM.
 
fundytides said:
I drove several Model A's back in the 50's-60's and I don't remember this as a problem
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I drive Model As almost everyday, and it doesn't happen. The part I'm talking about is Ed's opinion- "...quite common with a Model A". If it does, then I fix it.
 
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