IDPaul

I am having problems with vapor lock on my vehicle after driving in warmer weather and parking for a short (20-45 min.) time in the sun, the car starts fine and will drive for about 30 seconds before stalling.
No fuel observed from primary jets when actuating the throttle linkage and accelerator pump.
After short cool down with hood open, the engine will start and can be driven for hours with no fuel feed problems.
When cool in shop, fuel delivery is exceptional.
Have wrapped the pump to carb line with proper heat protection product. Thermo-Tech line cover with an added covering of Thermo-Tech Express Sleeve.
I am thinking of putting an in-line electric fuel pump in and blanking off the existing pump pad. Suggestions? Pump source?

mike11

What year is your car? Assuming a standard mechanical fuel pump, you may have problems with your venting lines. Do you have a charcoal canister? Has that been removed and vent lines plugged? Has your fuel pump been changed from a stock one to aftermarket one with no return fuel line to the tank? If so, you could be drawing fuel from the tank via the mech. pump and the tank has no way to draw air in, causing vacuum in your tank. Do you have a solid gas cap or one that vents? When you run the car and then stop, try opening the gas cap and see if the tank has vacuum and draws air in. Vice versa if you let it sit in the sun for a while without running, if you open the gas cap and get a buildup of vapors escaping when you open the cap, then you definitely have a tank with only fuel being drawn from the tank and no air being allowed into the tank.

jim2527

I don't think an electric will solve anything.

To prevent vapor lock the fuel needs to circulate and/or remain cool.

Try insulating the carb from the manifold with a phenolic spacer, a heat shield will help radiant heat.


A small 'recirc line' t'd into the fuel line by the carb will help to keep the fuel cool.

69Vett

install the original 1/4" thick gasket, which thermally isolates the carb.
this will fix the problem of fuel vaporizing inside the carb.
switching to electric fuel pump does not help this problem.

IDPaul

1981 corvette. stock canister hook-up. original pump with return. No venting troubles.

Big2Bird

A stock 81? I doubt vapor lock is the issue.
Have you ever changed the filter sock in the tank?
How old is the fuel pump?
Check the fuel filter?
The rubber fuel lines ever been changed?
Using the correct "S" hoses at the pump?

Rescue Rogers

I've read on other forums that people do indeed go this route with success, but I thinnk you may want to see why it is happening if you have the time. I would try the wood spacer first and see if you get relief with it.

Greasyfingers Nick

do inspect the S hoses..a lean here can be a catastrophic fire.
please post what you find out..usually heat soak when parked but hot engine from a drive can cause a vapor lock no start..but yours starts and runs 30 sec..then later will run fine for hours..something else going on as already in other posts.

ronarndt

[QUOTE=IDPaul;1595320902]
I had a similar problem with my 68 convert with NOM 454. Engine heat would boil the gas out of the fuel bowls if the car sat hot for 15-30 minutes and required cranking the starter for 20-30 seconds to re-fill the fuel bowls. The insulator under the carb helped some, but the carb was usually bone dry if it sat hot for any length of time. Try the insulator first. I finally switched to an electric pump and when re-starting a hot engine, let the fuel pump run for ten seconds to re-fill the fuel bowls. This fixed the problem for me.