Vapor lock anyone ?

[slugish]

Trying to solve a problem thats driving me batty.

Any of you had any problems with vapor lock , or gas getting too hot because fuel line too close to headers etc. Have talke dto Summitt tech & a lot of others & my problem seems to be vapor lock . Have any of you wrapped your fuel lines with heat tape or header wrap & did that solve problem. Cant beleive Im the only one who has this problem. Will run good for a while , let it sit for a while , try to ctrank it & no go -- starter turns it over but no go . Will eventally start & run ok till it happens again / have been towed 3 times because of this problem. Thought I miight be fowling plugs , but SUMMITT TECH SAID if pliugs were fowled , probably wouldnt crank no matter how long it set. . ANYBODY?HELP

[1984 swb chevy]

That does not sound like vapor lock to me. If you have to get it towed even after sitting I would say you have a different problem. You should try checking for spark when this happens. It sounds like a heat related problem but not vapor lock. I hope this helps.

[imnezrider]

I will expect some disagreement, but I don't believe in "vapor lock". I would check your fuel pump pressure and volume. Both can be the culprit. If these are in specs, reroute the fuel line.

[manimal]

this is really old sckool,but try some clothes pins(wooden ones) clipped on the fuel line to the carb.
-Lance

[454HO]

Can you post some pics of your fuel line routing? How close to the exhaust is it? What are the outside air temps when this problem occurs? Does it ever happen at night when the air is cooler, or only on a hot day?

If the fuel vaporizes (boils) in the line before the fuel pump... it will not pump. The fuel pump is designed to pump liquid, not vapor. Gasoline is volitile, which means it vaporizes at a relatively low temperature. The fuel pressure is also a factor. Lower pressure (input side of the fuel pump) means a lower boiling point. Higher octane fuels are more volitile than low octane.

Take a spray bottle filled with water with you. If the problem occurs, try spraying the fuel lines with the water to cool them off. Not a solution, but may help you pin-point the problem.

[bw4sale]

I had an '85 that did that. Stock 305. We thought it was vapor lock at one time (even tried the clothes pin trick) but later decided it was something else. I can't remember exactly what. Sorry. I'd look for other culprits.

[larry may]

yipper put some clothes pins on the fuel line. Worked in the old days. Also make sure the fuel cap has an open vent as in not plugged

[slugish]

Originally Posted by 454HO

Can you post some pics of your fuel line routing? How close to the exhaust is it? What are the outside air temps when this problem occurs? Does it ever happen at night when the air is cooler, or only on a hot day?

If the fuel vaporizes (boils) in the line before the fuel pump... it will not pump. The fuel pump is designed to pump liquid, not vapor. Gasoline is volitile, which means it vaporizes at a relatively low temperature. The fuel pressure is also a factor. Lower pressure (input side of the fuel pump) means a lower boiling point. Higher octane fuels are more volitile than low octane.

Take a spray bottle filled with water with you. If the problem occurs, try spraying the fuel lines with the water to cool them off. Not a solution, but may help you pin-point the problem.

It appe3ars my fuel line goes toward the frame then cuts in under the engine / should be the same routing as all the 81-87,s. Ithought that the fuel line ran along side the inner frame right next to the header at one part , but I THINK THAT IS THE RETURN LINE. . Would too much fuel pressure cause this problem ? & what is the correct amt. Also one of the replys asked if it acted up whem the air temp. was cooler or hot. If I remember correctly , it happens most when air temp has got cooler, after its run ,got hot , then wont crank - past 2 times has happened at night . do run 93 octane % have a stock ac delco mechanical fuel pump . Thanks all of you for your help