HRSTZ

I have a fuel problem with a 1997 Z/28. The car will run great and start every time but after removing the gas cap to fill the tank the car won't restart. This has happened four times in the last week. Just yesterday I was diaging the car but it started every time, I finally removed the gas cap and it woudn't start back up. After it won't start it will just crank and I don't hear the pump or it may start and I still don't hear the pump but it runs untill the pressure bleeds off. The car has a new relay and fuel pump but did this before. I have tryed checking pump voltage and ground but after not starting yesterday I got under the car and tryed to test the wires but the car started back up and then started every time even with the fuel cap off. So I have not been able to test electrical wires during the problem. What do you think.

slopokrodrigez

Sounds to me like you have a leaky injector. It's leaking a puddle of fuel in the intake and it takes a lot of cranking or time for it to dry up. You can easily check for it by using a fuel pressure gage. Get a long hosed type and tape it to the windshield. Drive it around and see that it doesn't go below 42 PSI. Now if the injector leaks, the pressure will bleed off when you shut the car off. The pressure should remain high for a good long while after the car is off.

If the pressure bleeds off, you want to eliminate some other possible causes before you suspect the injectors. The first thing you do is pull the vacuum line off the fuel pressure regulator and see if it is wet with fuel. If it is, the diaphragm has a hole in it and that is most likely the cause of the problem. The fuel pressure regulator has to be changed.

the other cause of pressure bleed off is the check ball in the fuel pump but you already took care of that when you changed the pump so that isn't it.

If the injectors are leaking down, the best thing to do is have them professionally cleaned through the fuel rail. If that doesn't work they can be removed and cleaned. the last resort is changing them.

BTW the trouble shooting guide in the shop manual says that if the fuel pump relay fails, the oil pressure switch will pull in once the oil pressure gets up to 4PSI and powers up the fuel pump. So one of the things to check if you have a long cranking problem before starting is the fuel pump relay located under the drivers dead pedal. It may have a bad or corroded connection at the socket.

If the problem isn't fuel related, check the condition of the plug wires to be sure they are tight clean and not shorting. Look under the hood when its dark to see if you see fire works.

good luck

shoebox

I know the manual might say that, but since we only have one wire to the sensor and it goes directly to the gauge, it is not possible for oil pressure to affect the fuel pump relay. The pcm controls the relay and and has no way to know what the oil pressure is.

slopokrodrigez

OK I concede. I keep saying what the manual says and you keep saying No so I tracked down all the signals related to oil and have come to your conclusion. The only control signal to the fuel pump relay is from the PCM. I sit corrected. The manual is wrong.