1951 Plymouth: very hot coil, no start, why??

[Rusty_OToole]

In Brazil does your gas contain alcohol? In the US the alcohol content of the new gas formula, 10% or 15%,makes it prone to vapor lock. This is not a problem on new fuel injection models because the fuel is under pressure. But it causes problems on old cars with carburetors.

[JRA]

Unfortunately my car does not have a heat shield near the fuel pump. The gasoline in Brazil has from 20% to 25% of Ethanol. About 90% of cars produced or sold in Brazil currently are FlexFuel (gasoline/ethanol mix in any level), so this is really an issue in Brazil for antique cars. I use regular gasoline in my car, but there is premium gasoline available here (95 octanes), do you think it would be a best choice? This premium gasoline is unleaded and with the same proportion of ethanol the regular gasoline.

Despite the vapor lock, that may be a reality here our hot weather; the question I still have is: why does the car start imediately just putting the cold wet cloth over the ignition coil? I did this test already, when the car was hot, turned off the engine, and tried to restart 60 seconds later. It does not start, unless I use a new coil or use the cold wet cloth trick. Therefore, I think the vapor lock is not really affecting the issue. Maybe is the distributor condenser...something is overheating the coil and create all this difficulty.

Thanks,

JRA

[Guest bofusmosby]

The question would have to be, is there a spark coming out of the coil when the car doesn't start?

[buicknewbee]

Unfortunately my car does not have a heat shield near the fuel pump. The gasoline in Brazil has from 20% to 25% of Ethanol. About 90% of cars produced or sold in Brazil currently are FlexFuel (gasoline/ethanol mix in any level), so this is really an issue in Brazil for antique cars. I use regular gasoline in my car, but there is premium gasoline available here (95 octanes), do you think it would be a best choice? This premium gasoline is unleaded and with the same proportion of ethanol the regular gasoline.

Despite the vapor lock, that may be a reality here our hot weather; the question I still have is: why does the car start imediately just putting the cold wet cloth over the ignition coil? I did this test already, when the car was hot, turned off the engine, and tried to restart 60 seconds later. It does not start, unless I use a new coil or use the cold wet cloth trick. Therefore, I think the vapor lock is not really affecting the issue. Maybe is the distributor condenser...something is overheating the coil and create all this difficulty.

Thanks,

JRA

If you have a good spark when the coil is hot the rag isn't changing anything. It could be a coincidence that when the rags cools the coil that is when the vapor lock is finished. Waiting for the coil to cool could be just enough time for the vapor lock to work itself out. The only way to know is next time this happens to take an extra spark plug with you. Disconnect one of the wires and attach the spark plug to it. Have someone turn the motor over and observe for spark. If you have spark look elswhere. Vapor lock!

Darren

Darren

[Rusty_OToole]

Next time try putting the rag on the fuel pump. If my theory is correct your fuel pump or fuel line overheats, the engine stops, you lift the hood and let it sit for a few minutes, the fuel pump cools off and away you go. If putting a wet rag on the fuel pump cures the problem you know it was the fuel pump all along.

High octane gas will not help, it will make it worse. The problem is the fuel is too volatile. You want lower octane gas. Some people have found relief from this problem by adding kerosene or diesel fuel to the gas. Start with 10% and see what happens.

You could also try making a heat shield for the fuel pump. Make sure the fuel lines are routed well away from the exhaust.

[JRA]

Based on all these comments I did some tests on my car, and I believe vapor lock is the issue. I will install a heat shield on the top of the fuel pump, and I also intend to change the fuel lines for heat insulated ones. I just realized the fuel lines close to exhaust manifold are copper tubes, so this increses the heat in the fuel system. Any recommendations of heat insulated fuel lines?

Thanks a lot,

JRA

[Guest bofusmosby]

I noticed that on my 37 Pontiac, the fuel line going from the pump to the carb. goes right next to the exhaust manifold. With mine, I'm going to get some replacement copper tubing, and bend it accordingly away from the manifold. This way, the same type of line will be used, it will just have different bends in it. I have never experienced this problem with my car as of yet, but why not correct this problem before it occurs.