Sladebrice1

I have a 1996 lt1 stock. The car had been sitting for about a month before I bought it. Soon after buying it I replaced the fuel filter because the car had/has a resistance at WOT. When I turn the engine off and start it a bit later I have a hard time starting it and once started an old gas smell occurs. I have refilled the gas tank at least 10 times since I have bought the car. Any suggestions???

Injuneer

Where do you smell the fuel.... engine compartment, passenger compartment, exhaust, near fuel tank?

Sounds like you need to check the fuel pressure. Rapid loss of fuel pressure after the pump primes, but before you try to start the engine can cause extended cranking. It can be due to problems with the check valve in the fuel pump, a leaking fuel pressure regulator, leaking injectors or leaking fuel lines. A pressure test, with the car on the road , engine at high RPM/max load will tell you if the pump is unable to supply sufficient fuel.

Sladebrice1

The smell is coming from the exaust. I checked the fuel pressure once before and I remember the normal with ignition off being somewhere around 42psi but my car would not register on the gauge with ignition off. But was running around 35psi with engine running. Sound like my fuel pump? I cannot smell or see any fuel in the vacuum line off of the regulator, which I have heard that tends to happen if regulator is bad.? No sight of fuel around any injectors, and no fuel smell from engine compartment.

Injuneer

If the injectors leak, the fuel drips into the engine/intake runners.

Your pressure sounds normal - 43.5psi with the engine running at idle/vacuum line disconnected (GM accepts anything from 41-47psi), and a pressure drop proportional to intake manifold vacuum when you reattach the vacuum line. Yours sounds OK in that respect. The other thing you have to check is how fast the pressure drops after the pump shuts off. Turn key to "run" (not "start") and look at the pressure while the pump is priming. When the pump shuts down, the pressure should not drop more than 5psi in 10 minutes.

Do you have a catalytic converter? If it's been deleted, the exhaust is going to smell, particularly on startup. When the engine is cold, the PCM richens the A/F ratio. Leaking injectors will also cause problems with a fuel smell in the exhaust at startup. When you try to start the engine, put the accel pedal on the floor and hold it there. Then turn the key to "start", holding the pedal on the floor until the engine starts. If it starts quicker that way, it may point to the injectors, because holding the pedal on the floor puts the PCM in "clear flood" mode.

Sladebrice1

I believe I do have a catalytic converter, haven't really look. But thanks for that tip. It seems to start better with the pedal off of the floor. Every now and then I have to turn the key to on and back to off a few times before I can get it to start. I noticed that I have a steady arc on the back of the engine(driver side). Could that be part of the problem? What is the arcing being caused by? Any ideas??

Injuneer

Arcing is usually a faulty spark plug wire. A misfire will cause that cylinder to dump air and unburned fuel into the exhaust. The O2 sensors "see" the oxygen in the air (they can't "see" the fuel) and the sensors read "lean". In response, the PCM adds fuel to that bank of the engine - fuel that it doesn't need - and now you have one cylinder in the bank misfiring and dumping fuel into the exhaust, and the three healthy cylinders running pig rich and dumping more fuel into the exhaust.

You will get the same results if you have an exhaust leak before the O2 sensor. The fast moving exhaust educts air into the system, and the O2 sensors read lean, the PCM dumps fuel. Runs rich, smells rich.

Sladebrice1

Ahhh!!! Sounds like I need to start there then, correct? Could that be causing it to be hard to start?

Injuneer

For the "hard start" I'd check the fuel pressure bleed down. Will it start faster if you turn the key back and forth from off to run three or four times before you try and start it?

Sladebrice1

Yes, it starts easier that way

Sladebrice1

If the pressure drop rapidly, does that mean its the regulator of the check valve??

Injuneer

That's about as clear as I can make it

Sladebrice1

Thanks a lot for the help. One more question. Is it normal for the fuel pump to run constantly while the engine is running??

Injuneer

Yes.

Sladebrice1

Thanks much Fred.