Car won't idle--any thoughts?

[Guest P12]

Hello everyone. I was wondering if I could get some input from you all? I am having carburetor problems with my '41 Plymouth P12. The engine seems to run fine under a load (though there is an occasional hesitation if I accelerate suddenly), but stalls whenever I disengage the clutch to come to a stop, and just wont idle for any length of time when I start it up. I have been using the throttle control to give her some extra gas to keep her going, but even that doesn't always work. The car does start up ok. The carburetor has been cleaned and new needle valve put in it. Any thoughts?

Bruce

[Guest P12]

More info on this--just went out and started her up. As usual this involves using throttle and choke. I found that when the engine warms up, I can close down the throttle and push in the choke almost all way, but if I push it in the last little bit (1/4 inch or so) she dies. I also found that when she is idling with the choke out a bit like that, I can goose the gas peddle and engine will accelerate smoothly, but when I let off the gas, she stalls. It would be nice if there was a place to post videos on this forum so I could SHOW you all what I mean.

Bruce

[Larry Schramm]

Just a thought but fuel filter, restricted fuel line, or possibly a weak/leaking internally fuel pump? Do you know what the fuel pressure is at the carb?

[gregchrysler]

some cars had an anti stall device on the carb my 49 Chrysler does

[Beltfed]

Check for a vacuum leak. At idle the leak is enough to stall the engine. When 'on the gas' the leak is minimize by the volume of air through the carb.

[GLong]

The fact that the car will idle with partial choke means that the idle mixture is too lean. Clean the carb again, focusing on the idle circuits.

As mentioned above, check for vacuum leaks.

Greg L

Edited October 6, 2013 by GLong (see edit history)

[Ron42Dodge]

One thing to check that I just went through is the wire connection on the back of the ignition key switch. I had one of the nuts get slightly loose and the car would run great and then suddenly die. It started to die about a minute or two after I would start the car. I believe the key in your Plymouth activates the ignition. I could get spark when sitting still and checking things but the engine vibrations would apparently vibrate the wire connection. I found the nut slightly loose. A 3/4 turn and everything ran so much better.

Ron

[Guest cben09]

The smallest passage for gas is the idle jet,,and the first to clog,,

There is usually an idle screw to be adjusted,,mixture,,not speed,,

That one usually is an AIR bleed,,so screwing it in richens the mixture

[provided there is gas comming from the jet]

Sometimes,,,,,,take out idle screw,,,give a toot with the tyre pump

and see if it will dislodge a piece of dirt,,,the hole in that jet is only

perhaps ,020-,030"dia,,If you had it on the bench,,Pull a wire out of a

wire brush,,,to poke through,,Just sayyin,,,

Hope this helps,,Cheers Ben

[Beltfed]

"Madison"....Huh?? It's hard to clean vacuum.

[Guest Flivver250]

Check for a vacuum leak. At idle the leak is enough to stall the engine. When 'on the gas' the leak is minimize by the volume of air through the carb.

I concur with Beltfed. I would look for vacume leak. If you can't find one, adjust your carb (I assume you have adjusted the mixture anyway) to the highest level of vacume. Whenever I am stumped I go back to zero and check timing, spark, and fuel. As wrenching is therapy for me, I enjoy starting fresh. How well to you trust the carb? It may need a rebuild which should not be a challenge (famous last words).