Humfreeze

25 man hours later still cant get car started. I originally got a Service ride control light on and a test revealed that the right rear sensor couldn't find the end stop. So I pulled the shock and found that the gear inside the sensor was indeed shatered. Sent part off to Capn Z for rebuild and got it back within a week. Installed part and turned intion on to run test and whala test checked out good. Start car and it fires right up. Runs for about 30 seconds and died in the driveway. WTF.... I started checking by checking connections. So far I have changed the Fuel pump and filter and the fuel pump relay. I did this because after determining that the ignition system was actually sending spark to the #1 plug, I sprayed a little starting fluid into the throttle body and the car started and ran for about 3 seconds and then shuts right down. I then tested the fuel injectors to ensure that they had 12v at eack injector which they do. I then pulled the cap and rotor and replaced them since i had it apart already. I also replaced the Ignition modules also. But still no start. I then test the TPS and it measures exactly the way it is suppose to. It just seems that this is a fuel problem since it will start with starting fluid introduced but immediately shut down. Could the ECM be bad and does anyone have any idea how to check this before I buy another unneeded part.

Sweet 90

Need to check your fuel pressure. There is a schrader valve on the Pass. side of engine. (looks like a tire valve with a little black cap) Attach a pressure gauge and tell us your pressure reading.

Humfreeze

I did test the fuel pressure and it was a solid 50 psi when I turned the key on. However, when the pump turns off after the initial 2 sec on period when the ignition is turned on, it tends to bleed down to about 25 psi. It seems like it should maintain that pressure in the system without the pump running. I was wondering if maybe when I raised the car while repairing the ride control system, if I had possibly crushed a fuel line but I inspected the lines and found nothing.

Thanks

FREEZE

Humfreeze

Another item that I did was in the FSM, it states to apply battery power to Terminal G and listen for the pump to run. I did that but can not hear the pump running. That was 1 reason why I initiailly changed the fuel pump. But maybe my hearing has gone bad from hanging around the jets I fly on base for 23 years.

ßill

Don't feel bad about not hearing the fuel pump run, I've had my Vette for 7 years and have yet to hear the pumps run. The pressure should not bleed off, that would indicate one or more leaking fuel injectors. Have you changed the fuel filter? A plugged filter could allow the engine to start then die. Thinking as I type, isn't there an interlock between oil pressure and the fuel pump?

Humfreeze

I replaced all the fuel injectors 5 months ago and yes I changed the fuel filter yesterday. It is tight and no leaks are noted. As far as the interlock between the fuel pump and the oil pressue, there is and the FSM states that when the ECM detects that 4 psi oil pressure is present, then the ECM sends a signal to the Fuel pump to run. When I crank the car, the oil pressure indicates on the Oil Pressure gauge in the vehicle. So I dont think that is the problem.

ßill

I'm not that familiar with the L98, so I looked it up. There are 2 oil pressure sensors. My guess is that one feeds the gauge and one feeds the ECM. Can you monitor the voltage at terminal G to see if the voltage goes away after cranking?

jd2

Just my 2 cents.....You say you check the voltage to the injectors. You should read about 17 ohms on the two pins at the top of the injectors when they are warm or hot. Since your engine won't run getting them hot is a problem. I'm not sure what they should read when cold. If one of the injectors is not reading enough ohms, the ECM will stop the motor. You say you replaced the injectors. I hope you didn't replace them with the Multec (grey/silver) original factory units. They are junk! I had three die in one week. I switched to the Bosch III sold by F.I.C.
Not sure this will help, just trying to get you going.

Hooked on Vettes

On a 90, pin G on the diagnostic connector is used to pull codes
via the CCM.

To test the fuel pump, you apply 12 volts to a Red wire that has
a female spade lug connector on it. The Red wire is located above
the battery and pokes out of a large bundle or wires wrapped in
convoluted tubing. As long as 12 volts is applied to that wire, the
fuel pump should run. The ignition key doesn't even need to be
on.

The fuel pressure will slowly bleed off after the pump is off.

Losing fuel pressure quickly could indicate leaking injector, bad fuel
pressure regulator (verify there is no fuel in the fuel pressure vacuum
line), bad check valve in the fuel pump, cracked or leaking rubber hose
connection in the fuel pump tank assembly.

Pinching off the fuel return line at the gas tank can help determine
where the problem is.

jeffp1167

By it starting and running for 30 seconds and then dying it sounds like pump is priming but then not running after engine is. I would check for fuel pump signal from the ecm or faulty ignition module (I know you replaced the module) Also try bypassing the oil pressure sensor above the oil filter with a jumper wire.

Humfreeze

OK i will try all of these ideas.
Just a thought... When I replaced the sensor on the right rear bilstein shock absorber... if it was not in the exact same location as the 1 on the left rear, do you think that this could keep the motor from starting if the computer detects that the ride control system is not aligned properly. Just a thought while I was flying this morning????

Thanks

Freeze