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Tippy 07-07-2001 03:14 PM

Diesel fuel for vapor lock
My Jeep vapor locked on me twice last week. I asked our mechanic at work about what to do and he said add 1 qt of diesel to the tank. Any body else have this problem and try this trick? How about a perminent fix besided adding an inline fuel pump.

My girlfriend said if I spent one more dime on my Jeep she would leave. Man I'm going to miss her!

Jim_Lou 03-18-2002 06:05 PM

Re: Diesel fuel for vapor lock
If you were in Nebraska last week, I really doubt that vapor lock was your problem. And if it was vapor lock, I don't think much of the diesel trick. It might help vapor lock, but will also lower the effective octane of the gas, and do bad things to the plugs, besides making the carb meter improperly.

Vapor lock is caused by fuel boiling in the pump and the supply line before the pump. The valves in the pump won't stop the vapor, so the pump quits pumping. The best cure for vapor lock is a return line to the tank, so that a continuous flow of cool fuel is passing through the pump.

I think your Jeep should have had this from the factory. If it didn't, look at a later model and copy what's there.

That's if you really have a vapor lock problem. I think something else is wrong, because your p[rofile doesn't mention any engine modifications. A stock engine shouldn't create so much heat under the hood that gasoline is boiling in March.

A clogged pickup could cause the pump to suck so hard that the pressure drop causes the fuel to boil in the line. That would be one thing to check if it is behaving like a classic vapor lock problem.

WILL 03-18-2002 08:51 PM

Re: Diesel fuel for vapor lock
Uh, that post was from July 7, 2001. That time of year, there would be vapor lock. Another phantom old post.

Tippy 03-21-2002 02:14 PM

Re: Diesel fuel for vapor lock
Yea, I have all that stuff, and no, it didn't do it last week. It only does it during the summer. I turnded the fuel filter so that the vapor return was to the very top, and with the diesel it does seem to help. Wonder why this post sprang up 8 months later?

Jim_Lou 03-21-2002 04:07 PM

Re: Diesel fuel for vapor lock
I guess its turning up had something to do with the new software for the BBS. The Gates works in strange and mysterious ways, my child. But if you're still having the problem, what does it matter?

Have you checked both your pickup line from the tank and the return line? A restricted pickup screen would have a double effect; it would reduce the flow so that you wouldn't have as much cool fuel passing through the engine compartment, and the reduced pressure on the suction side of the pump will make the gasoline boil at a lower temperature.

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