Hard to Crank After Stalling Out

[chance9888]

Hi all, new guy here. I just received control of a 1949 PW that had the engine completely rebuilt. Runs well, for the stage it is in. Anyway, if the truck is stalled out or turned off while the engine is hot, the thing is nearly impossible to to get going again. Ironically, if the engine is not hot, and hasn't been run for a day or so, it starts up first try. The only way i have been able to get it started again when it is hot is to pour a little bit of gas down the air-intake. I have no idea where to start, but here are a few things i have considered:

-Distributor Cap (I played around with this a little bit. Seems to not stall as easily after being fixed)

^^Engine Timing

-Carburetor?

I honestly have no idea. If anyone has a similar problem, please reply.

Thanks - John

[74w300uteline]

stab in the dark

Vapor lock? I don't exactly know what "vapor lock" is but the symptoms sound similar.

[chance9888]

Well, i described the problem to my uncle, who gave me the truck. He said it is plausible. Then, i looked on some threads and a lot of people said that they had installed electric fuel pumps in order to fix this problem. Ironically, he had an electric fuel pump at the warehouse where the Power Wagons are. As of now, i am convinced the problem is vapor lock. Between the engine's heat and Louisiana weather, that, very well, could be the problem. Also, can anyone tell me: If the timing is not set correctly on an engine, does it produce more heat than if it were set?

[Charles Talbert]

Well, i described the problem to my uncle, who gave me the truck. He said it is plausible. Then, i looked on some threads and a lot of people said that they had installed electric fuel pumps in order to fix this problem. Ironically, he had an electric fuel pump at the warehouse where the Power Wagons are. As of now, i am convinced the problem is vapor lock. Between the engine's heat and Louisiana weather, that, very well, could be the problem. Also, can anyone tell me: If the timing is not set correctly on an engine, does it produce more heat than if it were set?

Depends on exactly where it may be set. At any rate it should be set at 4* BEFORE TDC for optimum performance.

To prevent vapor locking, insulate the fuel lines with fiberglass sleeving, especially in the areas where heat will be high, (around the exhaust manifold, etc). Is your fuel pump heat shield in place?

If these fixes have no effect on the issue, then you will need to look in another direction. At this point I would run a compression test as the next step of elimination, low compression will cause hard starting after short time shut down like you have described, no need in spending $$ on trial and error repairs if internal issues are the probable cause.

[chance9888]

Wow, thanks Charles. I'll definitely look into that. I know, for sure, there is no fiberglass sleeving, but i'm unsure of the heat shield.

[74w300uteline]

what exactly is vapor lock?

educate me, how and why.

[Charles Talbert]

Wow, thanks Charles. I'll definitely look into that. I know, for sure, there is no fiberglass sleeving, but i'm unsure of the heat shield.

Fiberglass sleeve is available with heat resistance up to 1400*, maybe higher, not sure. It's easy, just slip over the tube and it will do the trick for high temp. If you can't find it locally, we can send you some, just let us know.

[Charles Talbert]

educate me, how and why.

Not a lot of time to respond right now, but basically it's this. Slow moving gas inside the line gets hot from engine heat, plus summer ambient temps. Gas will boil in the lines and small carb bowls turning liquid gas into vapor. Your engine will not run on vapor, thus it stalls and must cool adequately before it will restart. It is typical for this to happen when the vehicle is slow moving, such as in a parade, stop and go city driving, immediately after shut down on a hot day is famous for it, as heat levels surge way up as soon as the fresh air flow from vehicle motion and fan pull suddenly stops. As long as you are moving along at highway speed and getting fresh air flow, it isn't nearly as likely to occur.

[Clint Dixon]

The unofficial definition of vapor lock

educate me, how and why.

Vapor lock is caused by fuel in the the line (usually between the fuel pump and carburetor) becoming so hot that it boils. When the fuel boils, it turns from a liquid state into a gaseous state (vapor). The fuel pump can move liquid fuel, but it can not move vapors and as a result, the engine starves.

If you have a carburetor with a fuel filter that has a glass sidiment bowl, you may be able to actually see the fuel boiling in the bowl when vapor lock occurs. After the engine and the underhood temperatures all cool down, the vapors return to liquid and the engine can usually then be started.

Adding an electric fuel pump is not a fix to the problem. You need to keep engine heat away from the fuel line. The factory heat shield that is located between the fuel pump and the exhaust manifold is a must have. Also, as Charles mentioned, insulating the fuel line can help. It is also a good idea to get a longer tubing and install it between the fuel pump and carburetor. Route the longer tubing as far away from the manifold as possible. Mine is about located about 1/2" from the fender.

[Clint Dixon]

Charles, yoou beat me to the punch.

Not a lot of time to respond right now, but basically it's this. Slow moving gas inside the line gets hot from engine heat, plus summer ambient temps. Gas will boil in the lines and small carb bowls turning liquid gas into vapor. Your engine will not run on vapor, thus it stalls and must cool adequately before it will restart. It is typical for this to happen when the vehicle is slow moving, such as in a parade, stop and go city driving, immediately after shut down on a hot day is famous for it, as heat levels surge way up as soon as the fresh air flow from vehicle motion and fan pull suddenly stops. As long as you are moving along at highway speed and getting fresh air flow, it isn't nearly as likely to occur.

You must type faster than I do. ;^)

[chance9888]

@ Charles

So you guys can send me some? How much will that cost?

[74w300uteline]

Thanks Clint&Charles

learn something every day

[Charles Talbert]

You must type faster than I do. ;^)

I doubt it, timing just must have been on my side. You would have to look long and hard for someone who gets along slower than I do when it comes to typing.

[Charles Talbert]

So you guys can send me some? How much will that cost?

I'll have to check and see what we paid for what we have.

[olgraybeard]

I have the same problem in a VW bug is the fiberglass tubing made for this application, is it just fiberglass or does it have some insulation like what they use on larger pipes to keep from freezing. also been told but not confirmed to route fuel line so it slopes upward to electric fuel pump and then upward to carb so vapor isn't trapped in the line