1940 Dodge won't idle

[crazycars]

Hi gents,

          Have a problem and hoping someone out there has advice to offer.   After the motor self-destructed on my 40 Dodge, I replaced it with a 1937 Chrysler motor which, according to the guy I bought it from, ran good. Everything bolted up fine (had to do some fitting for the radiator as this motor was a little longer).  Starts up but won't stay running unless I keep continually pumping the gas.  The carb on it was a known good one but I replaced it anyway and results stayed the same.  Points and timing (almost new) are all at spec.  I'm gravity feeding it gas for now so the fuel pump isn't the source of the trouble. Only one source of vacuum and that's capped.  I tightened up the intake bolts but no difference. (can't keep it running long enough to spray the gaskets with carb cleaner to listen for speed increase).  Closing the choke and adjusting the idle seem to make little if any difference. Sometimes, while pumping it , I get a "lean pop", too. 

               I've worked on a lot of these cars over the years but have never run into this issue. 

If any of you have some ideas, I'd sure appreciate hearing them!  Thanks.

[F&J]

Old saying that 90% of carb issues are electrical 

 

Not there to see what you are doing/how much you are closing the choke... so try to keep it going at idle or slightly higher by sporadic spraying of carb cleaner.  If it seems to help, you have a fuel issue.

 

if it does not really help, it is likely electrical, timing or vacuum related.

 

The problem is that if it really is vacuum leaking, the carb cleaner might make it a tad better, to fool you to think it is carb plugged idle circuit.

 

 

when you idle, if all was good on any car, that is the idle circuit only, when you use the choke, you are adding fuel... coming through the main jets instead.  That is two different circuits.  Both can be faulty at the same time, but rare.

 

.

[PFitz]

Three things you said indicate the float level is too low.

1. Gravity feeding fuel to a carb that was likely float set for pressure feed will lower the float level.

2. Won't idle - only runs off the accelerator pump - happens when the float level is too low to pull enough fuel to the idle system.

3. Lean "pop", happens with a low float level.

 

Try hooking up the fuel pump, or raise the float level.

 

Paul

 

 

Edited May 8, 2017 by PFitz (see edit history)