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Hi,
Please help with this if you are able. I have a 95 lumina sedan w/a 3.1 v6 and I'm having trouble with the car starting when the engine is warm. After the car has been run up to temp. and is shut-off for 10 to 40 minutes, the car will start but runs like it has no fuel. It sputters and adding throttle does nothing and sometimes causes the car to die. About ten days ago this happpened away from home and (for some unknown reason) I decided to pour water (lukewarm) on the fuel rails and fuel psi regulator. Presto! the car immediately started and ran great as though it had never had a problem. This keeps happening whenever the engine is heat-soaked and won't run the water treatment always cures it. What is happening here?? BTW, this does not happen when the engine is cold. Also, when adding throttle slowly to accelerate, the engine runs fine; when adding throttle to 'pass' or accelerate quickly, the engine just lays down like it ran low on fuel or advance. Please help as people are starting to dis-believe the alternative fuel explanation.

thanks,

KP

richtazz

First, check the vacuum hose to the fuel pressure regulator. If there is fuel present, then the FPR is bad. This could cause vapor lock like symptoms.

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maxwedge

I'd also get a fuel press gage on it during the event and see what's what.

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Blue Bowtie

True vapor lock is all but unheard of in EFI systems. The fuel pump is in the fuel tank, and the use of a pump output check valve, pressure regulator, and fuel return line all but assure that having any vaporized fuel under pressure in the fuel system is impossible. Older engines with fuel pumps in the engine compartment required the pump to draw fuel all the way from the tank, and a heated fuel line could vaporize the liquid in that suction line, preventing the pump from drawing any liquid fuel.

As previously advised, pressure leakdown can cause symptoms similar to vapor lock, except it is caused by excess fuel instead of the lack of fuel. That leakdown can be through the injectors, or the pressure regulator vacuum pilot line.

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The exhaust does smell rich when the car sputters after a hot start; so I can understand the possiblilty of the fuel injectors leaking in to the cylinders. There is no gas smell under the hood nor any obvious signs of a faulty psi reg. (ie. leaks into the vaccuum line or externally) However, I don't understand why putting water on the fuel rails and psi reg. seems to cure this problem. If the injectors are leaking down and causing a pressure drop in the rails, could the remaining fuel in the rails be boiling and causing this problem? Any ideas? BTW Thanks for the previous help as it has helped me to understand this thing a little bit better.

KP

richtazz

I think you have an injector heat-sinking on you. When these injectors dead short, they can cause a loss of injector signal to the entire rail. The water trick cools off the bad injector(s) windings, and they will work until they expand with heat and short again.

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