Hey guys help me out here. My 91 Z Vert runs and drives fine. However, after it sits all night or all day while I am at work, it takes about 30 seconds of turning the starter before the engine finally fires. Then the "Service Engine Soon" light comes on. After the car is warmed up, it will start right up and no Engine light comes on. Someone told me it was the electric fuel pump, but I have tried turning the ignition on for several minutes before starting the car, and it makes no difference at all, still won't start right up. So, any ideas anyone? I bought the car about 2 months ago and immediately changed the fuel filter, plugs, plug wires, and a K&N distributer cap and rotor. Also replaced the PVC valve and went with Mobil 1 synthetic oil. I took the car by Advance Auto and had them run it on their computer to see what the engine light would say, but we couldn't get their machine to talk to my car. So......Any advice will be appreciated! Thanks! Darren

 

Sounds like the fuel pump going bad.

 

If it runs fine when warmed up, the fuel pump probably has no serious problems.

Turning the ignition on and leaving it on before starting is doing nothing. The ECM will operate the fuel pump relay for a two-second prime cycle only, regardless of how long the ignition is left on. If the ignition is cycled off for at least 20 seconds, then turned back on, the pump cycle will repeat.

Also, if the ECM receives any distributor reference pulses, the pump relay should operate for two seconds after the last pulse is sent.

Turn the ignition ON, then listen for the pump cycle. If you do not hear the pump run, suspect a relay problem.

If the pump runs for two seconds, test fuel rail pressure. Expect 44 PSIG, ±3 PSIG. If pressure is below normal, and or falls off rapidly after the pump shuts off, suspect a pressure regulator or injector leakage problem.

If the injectors are leaking, you can hold the accelerator pedal at 80% open or more to prevent injector pulses during cranking.

Advance Auto likely used the wrong kind of scanner. All you need t retrieve error codes from the ECM is a jumper wire, paper clip, guitar string, or other conductive piece.

With the engine and ignition turned off, locate the ALDL connector under the dash, just to the right of the steering wheel in the driver's foot well area on some models, and on the left on others, depending on the make and year. There may be a small rectangular cover over the access hole in the lower dash trim.



Insert a jumper tool or the aforementioned paper clip into the 'A' and 'B' terminals on the ALDL connector:



WITHOUT STARTING the engine, turn the ignition to the "RUN" position. Watch the Malfunction Indicator Lamp (MIL) - it will begin to flash. This is also commonly called the “Check Engine”, “CEL”, "Service Engine Soon" or "SES" lamp. The first code sequence will flash three times, and will usually be a code '12'. This is encoded by one flash of the lamp, a brief pause, then two successive flashes of the lamp followed by a longer pause. Each code will repeat three times, so you should see a "Code 12" flash three times. Any other error codes will follow in numerical order, and each code should flash three times. After all codes have been displayed three times, the "Code 12" will again flash three times, then all other codes will follow as described earlier. This cycle will continue until the jumper is removed or the ignition is turned off.

After you have made a note of all error codes, turn off the ignition and remove the jumper immediately. If you forget to remove the jumper and attempt to start the engine with it in place, you could damage the ECM. For this reason you should remove it immediately.

Once you have a note of all error codes, check this file for the decoding:

GM Error Codes.pdf.

You'll need Adobe Acrobat Reader to open/print the file.