JBJrC4

This is a 91 Corvette 6 speed with 50K miles that's been sitting for a while. I just replaced the fuel pump, fuel filter, spark plugs, and battery. It'll start for about a minute, then die. After that it will just continue to crank and won't start unless I wait a few hours then it'll do the same sometimes. I removed the old gas and added about half a tank of new gas. I checked for spark by removing the plug and hooking it to the boot touching bare metal while my brother cranked the car and the spark wasn't that big. I tried spraying starting fluid through the throttle body while the car was being cranked and it started, but struggled to stay on. The ignition module checked out as well when I had it tested at O'Reilly's. Any idea what it could be? Thanks.

whalepirot

No fuel. Most of that system is okay, but if you jump two connectors on the ALDL, it'll probably run; the pump AND the engine. It sounds as if the initial 5 sec key-ON pump run is fine, telling me the above.

I don't recall which two ALDL pins to jump, with no references at hand. I thought there was an oil pressure switch which signalled to FP to keep running after the initial prime. The 'jump' referenced, bypasses that.

JBJrC4

Yes, I can hear the pump prime.

whalepirot

Yup. Then it stops?

JBJrC4

Yes, it stops after it primes.

billschroeder5842

Maybe something here borrowed from a previous post that ties in loss of oil pressure (or faulty switch) with the fuel pump/relay shutting down:

Lots of people believe loss of oil pressure will cause complete loss of power to the fuel pump. Not true. Remember, the switch is wired in parallel with the fuel pump relay.

When looking back by the distributor, you should see an "oil manifold" with two electrical connectors mounted. Here is where the fun begins.

The "Oil Pressure Switch/Sensor Assembly" (around page 8A-20-6 Model Year 90 L98 electrical supplement) sends a signal to the analog oil pressure gauge. This is the unit's sensor portion. The schematics show the "switch" part heading for the fuel pump. This switch closes around 4 psi and provides the back up fuel pump power.

Continuing on, the other little widget mounted back there is the "Oil Pressure Switch". For this critter, head for page Central Control Module 8A-50-4 (MY90). You will see the circuit provides a ground for the "Check Gauges" indicator control and is CCM/panel light oriented. Keep in mind, the schematics differ on pre 90 units as they had no CCM but do have oil pressure warning lights. Not sure how they are wired. Don't have the manuals. Pretty sure the 90/LT1/LT4 are similar. They both have CCM's and mixed dash.

Good luck!

cshuman

Check the coil in the distributor cap. I have a remote coil and MSD 6. Mine started doing something similar. It would run for a while, shut off, then when it cooled down it would start again and do it all over again. Turned out my coil was opening when it got hot and then when it cooled down it would cycle again. You should be able to take it out of the distributor and take it to one of the parts stores and they can check it for you. If its not that it could be the module in the distributor, it also can be checked at the parts store.

topfuel67

My friends 89 did the same thing. Ended up being the icm. My 89 did that a few months later and I replaced my icm, problem solved.

JBJrC4

The ICM on my car is the original from the factory and it checked out when I took it to get tested. I ordered a coil so I'll see if that works as well. Not sure if the ICM could still be bad since it's the original though. Sometimes they work, but not 100 percent.

woody41

My 91 was doing the same thing, replaced everything from fuel cap to injectors, ignition module to spark plugs, all new sensors. Still would start and as soon as I touched throttle it would die and not restart. Had car towed to local shop (they have a C3 body for their sign). Checked exhaust system, which was original. Both of the pre-cats were not flowing, one was collapsed the other was clogged. Replaced all 3 with a new high flow single cat. Solved the issue. Runs like a new car. If your exhaust is original would be worth checking for flow. Car had been sitting about 3 years when I bought it from original owner, 77,000 miles.

JBJrC4

It actually still has the original exhaust and the car was sitting for a while before I bought it. I ordered new injectors, but I also ordered them because 4 of them had bad resistance.

whalepirot

Observe a taped-to-the-windshield FP gauge to see if the pressure drops just as the engine dies. Obviously, with no FP, no amount of spark will keep it running!