vapor lock...just curious

[Scott754]

I have a '35 Fordor and 'think' I just had a vapor lock issue this past weekend. I had replaced the coil last week (spark looked weak) & it started right up that day & a couple days later, I drove for about 30 mins in 90 degree heat and cruising in 3rd gear I lost power and couldn't restart it. After about 20 mins it started again (after it cooled down a little); I wrapped the fuel line in tin foil & its run ok since then. Someone suggested putting in a fuel line check valve. Does anyone have recommendations for/against adding a check valve, and also better insulating the fuel line? I'm not sure if the tin foil is effectively reflecting heat from the fuel line or acting as a heat sink drawing heat away from the fuel line? Someone also suggested insulating the fuel line with wire loom but I'm not sure if that's a good idea ... even though the engine throws off a lot of heat, I don't know if its hot enough to cause problems with wire loom, but anything with a cloth cover doesn't seem like a good idea?

[ford38v8]

Originally Posted by Scott754

I have a '35 Fordor and 'think' I just had a vapor lock issue this past weekend. I had replaced the coil last week (spark looked weak) & it started right up that day & a couple days later, I drove for about 30 mins in 90 degree heat and cruising in 3rd gear I lost power and couldn't restart it. After about 20 mins it started again (after it cooled down a little); I wrapped the fuel line in tin foil & its run ok since then. Someone suggested putting in a fuel line check valve. Does anyone have recommendations for/against adding a check valve, and also better insulating the fuel line? I'm not sure if the tin foil is effectively reflecting heat from the fuel line or acting as a heat sink drawing heat away from the fuel line? Someone also suggested insulating the fuel line with wire loom but I'm not sure if that's a good idea ... even though the engine throws off a lot of heat, I don't know if its hot enough to cause problems with wire loom, but anything with a cloth cover doesn't seem like a good idea?

Scott, There are several causes of the symptoms you describe, and many more ways to address those problems, each with varying degrees of success. As both electrical and fuel issues can prevent an engine from running, a "fix" to the wrong issue at the right time can appear to solve the problem, while in fact conditions may have changed while performing the fix.

The old days were simple: Open the hood, replace the coil from your stash of several old coils you keep in the trunk, start the engine and drive away. Alternatively, slap a towel over the fuel pump and douse it with water. Curiously, both fixes do work for most causes, so think about what elements those two fixes share: Hood open, and the passing of time. Excess heat underhood is at the root of the problem, and both fixes had a beneficial effect on that shared cause.

Of the many "fixes", there are several standout winners:

Remove your hood and be happy.
Replace your coil with a rebuilt.
Install an electric fuel pump.

The list goes on and on, and of course there are few who would remove their hood, but it can be a valid solution to part of the problem. Just keep in mind that the one single fix that always helps is the passing of time and the cooling of the engine's fuel and ignition systems.

[drolston]

Had the problem of not starting after a run on a hot day, even with every anti-vapor lock precaution: electric fuel pump at the tank, phenolic spacer under carb, and 2" aluminum risers on top of that. Checked spark and it would barely jump 1/4 inch with a weak yellow spark. Pertronix ignition with the correct 40,000 volt coil (with built-in resistor) and wound center ignition wires cured the problem. It will jump over 1/2 inch with a blue-white spark.

[George/Maine]

I had a problem like that when I bought my 39 with 51 engine. It had a 12 coil and resister would run good but getting gas and hard starting. Problem when changing to 12 volt they didn't remove the resister under dash. my guess.

[Scott754]

Originally Posted by ford38v8

Scott, There are several causes of the symptoms you describe, and many more ways to address those problems, each with varying degrees of success. As both electrical and fuel issues can prevent an engine from running, a "fix" to the wrong issue at the right time can appear to solve the problem, while in fact conditions may have changed while performing the fix.

The old days were simple: Open the hood, replace the coil from your stash of several old coils you keep in the trunk, start the engine and drive away. Alternatively, slap a towel over the fuel pump and douse it with water. Curiously, both fixes do work for most causes, so think about what elements those two fixes share: Hood open, and the passing of time. Excess heat underhood is at the root of the problem, and both fixes had a beneficial effect on that shared cause.

Of the many "fixes", there are several standout winners:

Remove your hood and be happy.
Replace your coil with a rebuilt.
Install an electric fuel pump.

The list goes on and on, and of course there are few who would remove their hood, but it can be a valid solution to part of the problem. Just keep in mind that the one single fix that always helps is the passing of time and the cooling of the engine's fuel and ignition systems.

Thanks ... good common sense!

[jimTN]

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Rock auto has the 6v elec pumps at the best price I can find. I have one of theirs running on a 34 and it works fine.