1951 Plymouth stall issue when stopping

[hep2jive]

Hi group! I have a stock Plymouth with 3 speed trans. Rebuild motor has been running great- use as my daily driver.  Recently I changed the distributor cap and rotor.  Points are new, changed out coil wire. At the same time I THINK (can't remember)  I tuned up the carb. Then when I turned the car on it ran great and smooth but stalled after a few seconds. Now it randomly will shut off when slowing or at a stop sign...not all the time though. Drove 250 miles straight and it never did it. The 250 miles back home it turned off 3 times. Once at a stop sign and twice when I pulled over and had the car on idling. I've put the idle speed up higher see if that helps. What could this be? When the car stalls when slowing or stopped it will turn right back on like nothing happened. Car idles smoothly drive great... other than once in a while stalling while slowing like creeping speed or completely stopped at a light.

[kencombs]

First things that come to mind are:  One: great looking car.  Hard tops are so rare..   then, idle speed set to specs and carb float level.  Higher idle speed helps, higher float doesn't.   And maybe a card needle and seat that doesn't shut off well.

[Dodgeb4ya]

Love the first early Plymouth Belvedere hardtops...pretty rare to see them.

[hep2jive]

@kencombs Thank you for the compliment! I'm thinking it must be a carburetor gas/fuel issue more than electrical. All this started happening when it became warmer outside.  I was thinking about putting a cooler thermostat in the car too, a 160. Perhaps that would help.

[hep2jive]

All of a sudden it started doing this stalling problem as soon as I changed the distributor cap.....but it seems like a gas issue... 

Edited May 13, 2023 by hep2jive

[JerseyHarold]

Could be dirt in the gas tank that obstructs the fuel pickup in the tank occasionally.  Did this issue occur right after you put gas in the car?

[hep2jive]

@JerseyHarold hey no this happened right after I put in a new distributor cap,  oddly. I don't get it! Hahaha 

Edited May 13, 2023 by hep2jive

[Sniper]

Fueling issue?  Maybe, but  doubt it.  Sounds electrical to me and a 160 thermostat wouldn't do anything useful.

 

 

[hep2jive]

@Sniper yeah it seems either pretty both. I find it strange it started doing this the day I put the new cap on. Yet it's all set up correctly as far as I know. Only only happens when I'm slowing for a stop at like 10 mph or less.

[TodFitch]

The rule of thumb is that the vast majority of carburetor problems are electrical (that is not carburetor related at all).

 

The maximum vacuum your distributor will receive will be on deceleration. Since this seems to happen on deceleration or idling (another situation with high vacuum) and it started when you worked on the distributor, I would look closely at the wiring and conductors within the distributor especially verifying that nothing is shorting out when full vacuum is applied to the advance.

[hep2jive]

Thanks for the input! @TodFitch

 

The distributor I used is # AL-106 and has a "2" inside the cap....the original cap I had on before this stopping problem was AL-138....with a "4" on the inside of the cap. Maybe it's the wrong cap? Yet it fit...

Edited May 13, 2023 by hep2jive

[rallyace]

I agree with Tod.   Check to make sure that the wires to the points and condenser are not shorting out when the vacuum advance moves. It is not an unusual happenstance. Check the braided wire as it is uninsulated and flexes with the advance. Sometimes a loose wrap with electrical tape will solve the problem.

[kencombs]

4 hours ago, TodFitch said:

The rule of thumb is that the vast majority of carburetor problems are electrical (that is not carburetor related at all).

 

The maximum vacuum your distributor will receive will be on deceleration. Since this seems to happen on deceleration or idling (another situation with high vacuum) and it started when you worked on the distributor, I would look closely at the wiring and conductors within the distributor especially verifying that nothing is shorting out when full vacuum is applied to the advance.

If my memory is correct (not a given these days), all the sixes used ported vacuum, taken above the throttle plate so decel vacuum would not be applied to the advance unit.  

but maybe happens when the advance goes back to full retard.   But, I still go back to my rule, look at the last things changed, carb work and distributor cap, even though I can't imagine an intermittent cap that causes a dead stop.  More common to cause misfires.

[Dave72dt]

Verify you have the correct cap according to the distributor number as well as any other distributor parts you may have installed.

[Tom Skinner]

hep2jive,

I agree with Dave72dt, Get the right cap on there. another thing is my Coil was going bad last summer and my engine died at slowing down several times,

coming home from rides. Ignition Coils I was told at my Local NAPA usually only last 6 - 7 years at best. I still think you need a Cap with No. #4 in it.

Good Luck running down the problem.

Tom

PS. Very nice car you have there!

[joecoozie]

Why did you change the cap in the first place?

IF the car was not doing this with the original cap then put the original one back on and see if that eliminates the problem.

If not then you can go from there.

[Dodgeb4ya]

BINGO!^^^^^^^^^^

[Bryan G]

I can dial the idle way down on my car, but then I have trouble with stalling when it gets warm. I blame it on some vapor lock going on; fixing my broken heat riser could help there I've found some success by tweaking idle mixture, idle speed, and timing, and then doing it all again a few times until you reach the best all-around situation.

[hep2jive]

4 hours ago, Tom Skinner said:

hep2jive,

I agree with Dave72dt, Get the right cap on there. another thing is my Coil was going bad last summer and my engine died at slowing down several times,

coming home from rides. Ignition Coils I was told at my Local NAPA usually only last 6 - 7 years at best. I still think you need a Cap with No. #4 in it.

Good Luck running down the problem.

Tom

PS. Very nice car you have there!

 Hmm interesting! Yeah tonight the car backfired while slowing down and died out! Perhaps it is the coil! I'll change the coil out tomorrow....I put the original cap back on ran fine for about 10 miles. Then I tuned the carb and lowered the idle speed that was pretty high went 10 mile back home and car backfired while slowing and died. Ugh! 

[hep2jive]

I put the original distributor cap on last night. Car drove fine until when slowing from 50 MPH  she backfired and then stalled.

[Dodgeb4ya]

Bare wire in the distributor grounding out as vacuum advance moves the base plate?

[kencombs]

2 hours ago, Dodgeb4ya said:

Bare wire in the distributor grounding out as vacuum advance moves the base plate?

Yeah, the backfire info wasn't in the OP, when I answered the first time.   If 'backfire' is a big bang out of the tailpipe, it could be an intermittent loss of ignition causing raw gas to light off in the muffle/pipe.  And that little wire in the distributor is often the culprit.  If a pop back out of carb, different story.

 

Kids used to do the ignition off, coast, back on to create that BANG back in the day.  

[hep2jive]

@kencombs hmm interesting.  Yeah I'll re-check the wire in the carb.  I thought maybe a bad coil might be doing it too. If I turn my idle speed up pretty high it doesn't seem to do it.

 

We're talking about the wire that connects the two plates to the left of the ignition points correct?

[Sniper]

1 hour ago, kencombs said:

If 'backfire' is a big bang out of the tailpipe,

 

That's a misfire, tend to make the mufflers swell up.

 

1 hour ago, kencombs said:

If a pop back out of carb

 

That is a back fire, as in it went back out the way it came.

[FarmerJon]

Check the wire in the distributor for shorting, check the distributor point plate is insulated from the distributor body, check the vacuum advance canister and line for vacuum leaks, and may as well check the points plate for free movement. 

 

From there, I would check the hose for your Vacuum wipers ( usually on manifold, under carb) make sure that it didn't deteriorate or get knocked loose when you did your tune up.

Check the carb and manifold for vacuum leaks. Spraying carb cleaner into the airstream will slow or kill the idle, so if you spray it around the carb gaskets, intake flanges, any where you suspect a leak, it will do the same if it IS leaking

Check spark plugs by misting with water while running in a dark environment. 

Check the coil with a voltmeter, I would do it after a drive so it will be operating temperature. 

Good luck