Issues with my 1939 Plymouth

[Paul Roa]

good afternoon to all

first thank you all for your guidance its really helpful. i have a 1939 with a 218 motor. thats the way i bought it. my original problem was the car would not fire up but after assistance from you all and my mechanic friend it fired up. it needed timing, points and condenser, coil, spark plugs and cables, new 0 gauge battery cables, new battery and it fires up. BUT my problem is once i let it warm up i can pull it back and if i turn it off it wont fire back up. i live on a hill and if i let it roll and jump into first it fires up. but that shouldn't be the solution. any ideas? my boy thinks it might be vapor lock, we had this similar issue many years back on my 38 chvey truck. thanks in advanced

[PT81PlymouthPickup]

Does it crank over strong when you're trying to start it the second time?

[Plymouthy Adams]

as you stated, larger sized battery cables. do a voltage drop test also....check the current draw on the starter for possible armature drag due to worn rear busing....a bit f a problem in these three areas combined will drive a nail in most all coffins....will rob the system of current for the ignition evident by the ready start with out the starters use....what is the compression readings and the state of tune, these will also add to any of the prementioned items...good valid reading and you will no longer be guessing at what it may or may not be...while you still may have issues due to low compression and what not, you can rule out the electrical

[knuckleharley]

What is the reading on your water temperature guage when you try to restart it?

 If it's not boiling,it's not hot enough to vapor lock.

 

I am guessing the problem is not vapor lock,though. PROPABLY ignition or carbuerator related. Maybe timing.

 

Check your gas lines to make sure none are running too close to the exhaust manifold,tailpipe,or even the engine.

 

Could be your timing is too high. Does it seem like the engine wants to "kick back" when it starts,or maybe sputters until it starts? Get it running again,let it warm up to normal operating temp,and then loosen the distributor clamp and advance and retard the ignition until you find the "sweet spot" where it idles smooth. Retighten the clamp and start it again.

 

This is common with old cars that have timing chains that have stretched and timing gears that are worn. What I suggested above is often just a temporary fix. IF this "Fix" "cures" your problem,plan on buying a new timing chain and gear set and crankshaft front seal because it ain't going to get better.

 

 

Edited March 10, 2021 by knuckleharley

[Merle Coggins]

When you try to restart it hot, hold the throttle partially open while cranking. Often times the gas in the float bowl will expand from heat soak and flood the engine slightly. Opening the throttle allows more wire in to offset the extra gas in the manifold and it’ll fire right up. 

[tom'sB2B]

You could also lower slightly the carburator float level. That helped me with my hot starting issues.

Good luck

Let us know what works.

[keithb7]

An easy check when it's hot and won't start: Remove the engine air filter. Look down the carb venturi. Cycle the throttle linkage a couple times. Look for raw fuel squirting into the carb throat. The accelerator pump squirts it in there, when it's working right, and when there is fuel in the carb bowl. If there is no fuel in the carb bowl, is it evaporating? Could be.  Why is there no liquid fuel being pumped back into the carb bowl? Vapor lock could be an issue. Remove the fuel line where it enters into the carb. Hold it into a bucket or bottle. Have a friend crank the engine over to activate the mechanical fuel pump. Is there liquid fuel pumping out of the fuel line? If not, you seem to have a fuel delivery problem. Let the car totally cool down and try this test again. Maybe let it sit overnight. In the morning, now is there liquid fuel pumping out of the fuel line, while cranking the engine over? If yes, you likely have vapor lock issues. Try non-ethanol fuel. Is your heat riser valve in the exhaust manifold stuck open? Overheating the carb? Check it out. 

 

If you do have good fuel delivery, & good compression (when hot) , good chance its something in the ignition system.

 

I like to use my own screw-ups as examples to help others. One time I set my engine tappets incorrectly. I was learning. Boy did the engine run quiet and smooth! I was proud. Then everything heated up. Valve stems elongated. Valve lash decreased. Hmm, the noise out the exhaust sounds off.  "Something is awry" I thought. By now I had poor cylinder compression and my hot engine would not start. The exhaust valves were not seating properly. When I let everything cool down, the  valve stems shrunk again. No problem. The engine fired right up. I re-set the valves properly. Licked my wounds, checked my pride, and we were all better off.

Edited March 11, 2021 by keithb7

[greg g]

Is the base of the carb where it mates to the intake wet or gas stained?  Do you have a phenolic spacer between the carb and the manifold?  Hot start problems are pretty common as under hood temps go up, when you shut down from a drive fuel in the float bowl will expand and over flow the bowl fluid bass puddles on top of the throttle butterfly and accumulates in the intake.  So you have a flooded engine.  The last thing it needs is several more pumps from the accelerator pump. Slowly open the throttle to wide open before cranking the starter.  As noted above a slightly lower (a couple 32nds) mmay be enough to address the situation.  If not you might want to put in the spacer and maybe make up a sheet metal heat shield to extend between the float bowl and the intake manifold.  The spacer blocks can be had for 10 bucks or so from the Landon's stovebolt website you will need an extra carb base gasket so get one of those also.  Probably need longer studs to.

Edited March 11, 2021 by greg g

[Sam Buchanan]

The heat shield I fabbed:

 

 

Does it work? Don’t know.....

[keithb7]

1 hour ago, greg g said:

The last thing it needs is several more pumps from the accelerator pump. 

My suggestion was a way to quickly determine if there is fuel present in the carb bowl. Not to try and start the engine after stroking the accelerator pump.
 

My experience is, with the air filter removed, looking down in the carb while cycling the throttle will give positive ID if fuel is present, or not. 

[Dan Hiebert]

Educational opportunity on my part here, did the 39's have the Sisson choke?  If not, read no further.  If so, I had the same issue with our 48 D24.  The Sisson choke was not working right, it would work well when the car was cold, but once it reached operating temperature, it wouldn't.  It would still fully choke the carb when starting the car hot, making the car flood out almost instantly.  I had to have someone hold the choke open to start the car when it was hot.  Couldn't find a replacement Sisson at the time and got tired of that procedure, so I just replaced it with a manual choke.   That was about 30 years ago, now.  I never delved into the "why" it didn't work, but that has since been discussed here in the Forum. 

[greg g]

Keith, my comment wasn't directed at your suggestion to visually check for fuel, but rather at the tendency of people to pump the accelerator when trying to start what is usually a fuel fouled intake manifold.