michael57

I am having intermittent vapor locks problems on my 68 roadster. It usually happens after driving for an extended period and coming to a stop. Any suggestions?

SIXFOOTER

Insulate the fuel line from the pump to the carb. Install heat shield between carb and intake. Have heard fuel pump can do it too when valves give out in it and the fuel can siphon back to the fuel tank.

michael57

thanks for the quick response...the carb. heat shield is already on the motor. I will order the fuel line heat shields today.

sweethence

Dont forget vented gas cap, and do you have the fuel return line set up still?

Also be sure it is actullay vapor lock, and not a clogged fuel line or fouled fuel pump....


I just went through this whole deal:lol

Running great now

michael57

thanks for the reply...the gas cap is venting....the first thing I checked when it stalled out was to remove the gas cap....i did not hear a swooshing sound of air rushing into the gas tank.....the return line is still in place.......it definitely is a vapor lock problem...after it sits for a few hours, it will start and run.

sweethence

Ok also check the position of the lines in relation to the lower radiator hose make sure is isnt touching, do you still have the solid steel line s from pump to carb? or rubber?

michael57

the fuel line going from the carb. to the fuel pump is rubber..it does get very close to the heater core hoses and the lower radiator hose...I don't think that would cause the vapor lock problems but I will cover it with Thermo-Tec heat shield anyway..I should upgrade my headers to ceramic coated to cut down on the engine compartment heat. that area where the steel fuel lines come into the engine compartment are very close to the headers on the passenger side of the car...thanks for your help

71406

I know I get some grief for suggesting this, but when I was a kid, my dad's 61 Mercury would get vapor lock...he tried everything but nothing seemed to work. He eventually pulled the thermostat and the car ran cooler and the problem went away. He would always pop it back in during the winter months for heat.

But first...how have you confirmed its vapor lock? Are you sure your carb isnt leaking fuel into the manifold after you shut it down causing it to flood? Many q-jets have been know to do that.

Z-man

- A phonelic carb spacer will get it away from the hot manifold.
- Try to buy gas without ethanol if you can find it.
- Also, 1 quart or so of diesel per 10 gallons will prevent vapor lock.

sweethence

how old is that rubber line?

give classic tube a call, and put the ss hard lines in
looks better too



PS dont mind the rest of the mess, Im a work in progress

been doing more driving then wrenching

michael57

A many thanks for all the responses

JPhil

Another phenomenon commonly called vapor lock is "fuel flash-over." When the engine is hot and you turn it off for a while, then jump in and take off at hard throttle (like when on a run with a bunch of C5s, or maybe robbing banks), the engine will die just about 3rd gear.
This is from the gas in the line between the pump and carb getting hot, but not hot enough to vaporize because it is still pressurized between the pump and needle seat. But when you drop the fuel level in the bowl quickly by hard acceleration, the float drops fast and far. The hot fuel rushing into the vented bowl is suddenly de-pressurized and flashes into vapor, like steam blasting from a pipe filled with hot water when you slam the valve open. This blasts pressurized vapor into the float bowl, blowing the liquid fuel away from the jets. Within a few seconds it has stabilized, and all is OK again. The only way around this, if the insulation doesn't help, is to let the engine run a few moments to let fuel level drop slowly and open the needle valve just a bit so the hot fuel in the line can enter the bowl slowly and be tempered until cool gas gets into the line. Then you can floor it.
I've done most of the things above, but this one has still gotten me a couple times. Now that I know what it is, it doesn't bug me too much, except that it usually hits me when I'm trying to be and I'm not paying attention to my car

John

P.S. Many years ago I was hauling 3 Harley 74s from So Cal back to Colorado in my 3/4 ton '59 Apache truck in August.The ol' 6-banger was running fine but started vapor locking in the mountains of Utah. I had mounted a windshield squirter unit from a Pinto on the truck, so I wrapped the fuel line with one of my bandanas and stuck the squirter hoses into it. Every so often I'd hit the switch and soak it. Worked great, no more vapor lock from Vernal to Boulder in 90* temps......