Vapor lock
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Joined: Jan 2002
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From: Midland, Texas
Vapor lock
Looked this up in the archives. My situation exactly... runs for 20 min. then fades away and wont restart until a cooldown period of about 10-15 min. This comes on the heels of replacing a distributor, coil and plug wires. Set the timing @ 3*btdc. Put a little aircleaner from my 3 deuce setup on the little dodge 2 bbl carb that came with the truck. Will be replacing manifold with the 3-2's when my grandson returns from his vacation. The truck starts instantly, runs fine... then the stalling. Vapor lock... or poor mechanicking? Thanks, Himmelberg
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Joined: Jun 2002
Posts: 344
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From: Lancaster, So Carolina
Vapor lock
Sounds like the dreaded VL to me.
There are many learned ones here to suggest things to try. THe key is that the engine's heat is getting at your fuel system and creating that vapor.
I chopped down my exposure to it by putting a full 2" plastic carb spacer (good insulation qualities) between the manifold and my Holley 1850. I remember my stock 2 bbl had zip there. The old 4bbl I removed from the manifold had about 3/8 aluminum spacer
There are many learned ones here to suggest things to try. THe key is that the engine's heat is getting at your fuel system and creating that vapor.
I chopped down my exposure to it by putting a full 2" plastic carb spacer (good insulation qualities) between the manifold and my Holley 1850. I remember my stock 2 bbl had zip there. The old 4bbl I removed from the manifold had about 3/8 aluminum spacer
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Joined: Mar 2002
Posts: 2,070
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From: Boise, Idaho
Vapor lock
Hmmm. The manifold heating system is a flapper valve in one of the exhaust pipes that forces the exhaust through the exhaust crossover when the engine is cold. Do you have that system still on your truck? Is the flapper valve stuck?
Maybe the problem is the fuel tank. Do you have a stock or stock replacement gas cap? If the gas cap is sealing the gas tank and not allowing air in, the gas won't be able to be pumped to the carb for long. The test of this is to remove the gas cap when the truck stalls after 20 minutes. Removing the gas cap will release the vacuum. The truck will start again.
Maybe the problem is the fuel tank. Do you have a stock or stock replacement gas cap? If the gas cap is sealing the gas tank and not allowing air in, the gas won't be able to be pumped to the carb for long. The test of this is to remove the gas cap when the truck stalls after 20 minutes. Removing the gas cap will release the vacuum. The truck will start again.
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Posting Guru
Joined: Jan 2002
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From: Midland, Texas
Vapor lock
Good observations. I wonder if my jagunda oil bath air cleaner acts as sort of a heat sink, Jay? I put it back on to try it out. I have recently replaced the gas filler cap, Paul. This and our rising desert temperatures may account for the problem that did not exist before. I have the ram's horn exhaust manifolds... and no changes there. Thanks, both. Best. Himmelberg
Last edited by himmelberg; Jun 23, 2003 at 06:50 AM.
