Sorry for new thread but my past post for titled fuel pump problem and it now seems the fuel pump is fine. This is where Iam stuck. Car starts and immediatly shut off. The way the mechanic explained it to me is.......when turing the ignition we get surge on the injectors and spark.After it starts and shuts off with the igntion still turned we loose surge of the injectors but retain spark............Sorry but does this make sense. He's out of idea's even with the fsm.

 

Have you checked fuel pump pressure? The filter could be clogged, or the fuel pressure regulator could be unhappy.

 

Your mechanic is wrong, very wrong. What year is your car?

 

year 1991...........I get 45-47 psi at the rail and holds.

 

Yeah,
I'd make him SHOW you the fuel pressure when the key is turned to ON...the pump runs for 2 seconds to prime the injectors and then shuts off UNTIL the engine is running. The fuel pressure at key ON should be approx 40 psi steady. No flickering or bouncing of the needle. If its bouncing around the filter is plugged.

The fuel pressure gauge shows you pressure & fuel NOT used. As the needle drops thats showing fuel thats being used. It should drop as the engine is revved....fuel used. Should recover instantly to whatever the reading was...around 40 psi.That means the pump is replacing the fuel that has been used. If the pump cannot do this, the gauge will show pressure going up/down bouncing around everywhere because the fuel cannot keep a steady flow to the fuel rails and the injectors...the filter is plugged and letting drops thru..not near what the engine is using. Pressure when running will be a cpl lbs less than key On pressure. If pressure drops instantly as key is turned off or when engine dies...thats a bad filter or bad pump. The fuel system should hold over 20 lbs for a DAY. Should hold the 35-40 lbs for several hrs.

Take the fuel relay OUT or disconnect it and start the car. It will have to crank longer but it will start. Observe the fuel pressure while doing this. Pressure tells all the stories by how, how much and when it comes.
This will tell you if the relay is shorting the pump circuit. When the relay is d/c there is a back-up system that allows the engine to run.

Go thru the distributer wires and inside the cap. The engine ECM gets the signal to operate the inj from the distributer. This tells the inj system that the engine is running. The key ON will give 2 seconds of fuel pump no matter what the dist is doing....but the dist has to provide the reference signal to the fuel injection or there will be NO fuel pump or injection....

Bottom line, all this can be looked at once you KNOW there is fuel pressure at key ON, and what that pressure does after the engine starts.
If your mechanic is worth his salt...he can jumper the fuel relay and make the pump run so the engine can keep running to help diagnose the problem...IF its an electrical issue. If its a plugged filter...then that will show up as little or no pressure at key ON and especially as the engine fires and uses what fuel the 2 second pulse provided. If the pump is running and there is no pressure...its the filter. Plugged filters will make the pressure gauge flicker and bounce around a LOT. A good filter & pump will create pressure and make the needle on the gauge as steady as a rock. The only time the needle moves is to drop 5 psi when the engine is revved.

Would'nt hurt to change the filter anyway. The pump & screen is next.....IF power is getting to the pump.

If the mech is going thru the FSM flow charts correctly then he has already done all this. There IS a conclusion in the FSM regardless of what he is coming up with. Go with the book. Its never wrong.

 

at key ON ? and with engine running?

see previous post as well.

IF there is pressure at all times and it holds, that indicates there IS reference to the inj circuit from the dist. Fuel inj control is working as it should mechanically to the point of the rails. Next is the injectors themselves.
Also IF thats a real pressure figure and its steady, the filter is likely ok.

Ohms test each injector. Should be near 16 ohms. Under 12 is junk and a slow inj although not dead. A reading of near zero is a short and likely the source of your headaches.

Next has to be spark....OR inj pulse failure. Test spark with a spark tester to SEE the spark and test the inj signals cranking the engine with a NOID lite to SEE the inj pulse.

d/c one inj at a time to see if there is any difference. A shorted inj will/can short out the entire bank...you have pressure but it can;t go anywhere because the inj are not opening due to a shorted or corrupted signal.One bad inj can possibly short the entire system. The L98 is bank-fired. Basically one inj circuit thats split into 2 sides with four leads each. One side fires then the other based on what #1 cyl position is.
Check for fuel in the oil and in the fuel pressure regulator vac line.

 

Shop is closed but first thing in the morning I will bring your suggestion. The fuel is holding and revieving 43 psi at the rail. He is also recieving spark at the distrib. He's gettin no voltage at the injectors after cranking.
Thank You for that write up... I will let you tomorrow what he says about the write up.

 

i am leaning towards the injectors getting hot and the resistance building up, which in turn shuts down the injectors pulsating.

 

But the car is not starting, it starts for a 1/2 second and shuts off. So it cranks but wont start.

 

I agree with leesvet. A shorted out injector is highly likely.