pacat

I Have a stock LT1 in a 1993 Corvette. About 2 weeks ago on the way home from work my car dies in traffic. I pulled off the side of the road and try to restart the engine. It would crank over but not start. I tried spraying starting fluid into the intake, it sounded like it wanted to run until I stopped spraying the fluid. I sat there waiting for a ride home. After sitting for about 10 minutes I tried starting it. It fired up immediately and ran great like nothing happened. I drive the car home (about 15 miles) no problem. The next day I drive my son to baseball practice (about 5 miles), runs great. 1 ½ hours later we get into the car to leave and it will not start. We get a ride home. I come back 1 hour later and it starts right up. I get it home
and I’m able to get it to repeat a no start situation by running the engine till it warms up to 200 degrees, shut it down for about 15 minutes, then try to crank the engine.
When I have a no start I get 40 psi at the fuel rail
I have installed Noid lights on the injector wires they do not light
I hooked up a timing light to the plug wires- no spark, not even at the coil wire


So far I replaced: fuel pump, fuel filters, OPTI is about a year old.

I’m thinking a bad ECM. Any Ideas, thanks

tspence45

iTrader: (30)

I'd look into the ICM. It's probably getting heatsoaked, and it's about had enough. My car's been doing about the same thing for the past year. But, it always starts on the 2nd try a couple minutes later. I'm going to try replacing the ICM, and see if that does anything for me.

pacat

Where do I find the ICM, and can it be tested?
BTW the car does not show any codes

john93m6z

I have a 93Z and it's doing the same thing. I have tested and found it to be the opti. The ICM (on Camaros) is located on the front of the driver side head, attached to a bracket with the ignition coil. I suspected my module of being bad and had it tested at Autozone. They didn't have it listed in the chart but all of the other modules that looked the same (impala SS and something else) took the same connector and code to test. It tested good, I bought a new one and that wasn't it. When I was able to get it to shut off long enough to test I found that I wasn't getting a signal to the module and tested the signal from the opti and that was it. Good luck.

pacat

As I stated before, when the car fails to start and I have the Noid lights hooked to the injector wires the noid lights do not flash when cranking the engine. Would a bad Opti, a bad ICM, or a bad ignition coil cause the injectors not to fire?

Also when cranking the engine (when the engine won't start) the oil pressure gauge on the dash does not move. When cranking the engine when all is normal the gauge will jump up to about 30 psi. If the ECM is not receiving oil pressure signal from the oil pressure sensor it may not let the fuel injectors fire.

shbox

If the Corvette does have an oil pressure safety switch (4th gen f-bodies do not), then it is entirely possible that it is shutting the engine down (though, it would be by fuel pressure and your fuel pump relay would have to have failed, too). The oil pressure switch is there as a backup to the fuel pump relay. If your oil pressure sensor has multiple wires going to it, chances are it does have the switch. Have you checked your oil level?

That said, it does not sound like your trouble.

The ICM would have nothing to do with the noid lights not working when it does not run. That would be the opti or ECM (including wiring/connections to them). Check your opti wiring harness for tight connection and any corrosion. Also look for any trouble codes.