Vapor Lock

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Jul 13, 2005 | 06:19 PM

JoeVB

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Vapor Lock

92 F-150, 351, 4x4, auto

I have a digital transmision temp. guage on my truck and when it gets above 185 my truck sometimes stalls. Someone told me this happens when the gas gets too hot in the fuel lines from the tank to the fuel rails.

The lines run along the frame rail from the tank and when they get to the bell housing of the transmission they are routed above the transmission to the fuel rails.

Is there an easy way to change the configuration of the fuel lines so they aren't in a place to get too hot? Or maybe just some way to easily insulate them in the position they are in?

Thanks,

Joe.

Aug 10, 2005 | 05:51 PM

Danny86E150

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Hmm.. you need to diagnose this as the problem for sure.. I wonder if that's what's happening to my van. I figured it was the TFI over heating.

Aug 11, 2005 | 02:03 PM

djkrs2

Cross-Country

Joined: Dec 2003

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From: Snohomish WA

That's very interesting. My '96 did the same thing twice... on 90 degree days. The first time it happened to my wife and I thought it was something she had done. The next day, it did it to me. Luckily it doesn't get that hot too often in Western Washington, but I'd like to know if there is a solution.

Aug 11, 2005 | 03:04 PM

lmadore

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Joined: Jun 2004

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From: Mid-Missouri

Vapor Locks don't happen on an EFI system.
I would be looking at other causes.

Aug 11, 2005 | 03:33 PM

JoeVB

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Quote:

Originally Posted by lmadore

Vapor Locks don't happen on an EFI system.
I would be looking at other causes.

Maybe I don't understand what vapor lock is then. Can you tell me why EFI systems aren't affected by this? Maybe I don't knwo enough about EFI.

Joe.

Aug 11, 2005 | 03:45 PM

MRL123

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Joined: Oct 2004

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From: Wetaskiwin, Alberta

Just a quick question for you JoeVB - does it not cause you any concern that your tranny temp is running so high at 185 degrees? From what I understand about oil temperatures, at 185 deg. , you are in the danger zone and on the verge of literally "cooking" your tranny oil. I could be wrong on this so someone call me on it if I am.

I just towed our RV 1,500 miles in some +90 temps and my tranny temp guage never, ever exceeded 170 degrees.

AFAIK an EFI system is pressurized at all times by the frame rail and/or in tank pumps and therefore it is thought to be impossible to get a vapour lock which is, I think, an air pocket in the lines. In your case though, with that much heat being thrown at the fuel lines, I don't know, I guess that anything could be possible.

Good luck and let us know what you discover as you troubleshoot the problem.

Cheers!

Mike

Aug 11, 2005 | 04:05 PM

lmadore

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From: Mid-Missouri

Basically a Vapor Lock is caused by heating of the fuel in the lines before it reaches the intake. The fuel goes from liquid state to vapor state. At lower pressures, this occurs sooner. A carbed fuel system runs at 7-8 PSI in most cases. It is much less likely to happen at high pressure. EFI is 30 to 40 PSI... The pressure modifies the vaporization point in a similar way that a pressurized radiator boil at a higher temperature.

Vapor locking can also happen at the carb in a carbed engine. The fuel vaporizes too soon and throws off the mixture (too rich).

Fords were notorious for vapor locking before EFI was introduced. I have never heard of a chevy with a carb vapor locking.