What the heck?.............
Thread Starter
4th Gear
Joined: Aug 2007
Posts: 4
Likes: 0
From: Terryville CT
What the heck?.............
Hello all. Another newbie here. I'll try to make this short. Bought my first Vette for my wife a few months ago. An '88 convert with the 4+3 tranny and just under 100K miles. It started and ran great (I thought) until I needed to take it through emissions in CT. After a major tune-up, new MAF, and new 'Y' pipe w/pre-cats ($2200 later) it finally passed emissions. Problem now is it's having a hard time starting. Cranking and cranking until it starts to go, and finally starts. Runs great after it starts. Mechanic thinks it's the oil pump sending unit to the computer to tell it to start.
Last night, the wife tells me the radio quit. Sure enough, I turn the key and no radio. Check the fuse, looks good and put it back. Lo and behold the radio works. This morning, the car won't start no matter how much cranking is being done. This evening I go try to hear if the electronic fuel pump is going while the key's on. No noise. I check the fuse. Looks good. I put it back in the slot, try to start it, and it fires right up.
What the heck is going on?
Last night, the wife tells me the radio quit. Sure enough, I turn the key and no radio. Check the fuse, looks good and put it back. Lo and behold the radio works. This morning, the car won't start no matter how much cranking is being done. This evening I go try to hear if the electronic fuel pump is going while the key's on. No noise. I check the fuse. Looks good. I put it back in the slot, try to start it, and it fires right up.
What the heck is going on?
Burning Brakes
Joined: Sep 2001
Posts: 1,013
Likes: 9
If you can't hear the pump run when you turn the key to the run position ... there is obviously something wrong in the fuel pump prime circuit. Get a Factory service manual, and check the relay and the wiring.
If it doesn't die once it is running, there is nothing wrong with the oil pressure switch. When you do get it to start, it is because you are getting enough oil pressure cranking it to activate the oil pressure switch, which then turns the pump on. Your cranking oil pressure is probably borderline to activate the switch ... Either that or you have something intermittent in your prime circuit wiring. Either way, something in the prime circuit is at fault.
If it doesn't die once it is running, there is nothing wrong with the oil pressure switch. When you do get it to start, it is because you are getting enough oil pressure cranking it to activate the oil pressure switch, which then turns the pump on. Your cranking oil pressure is probably borderline to activate the switch ... Either that or you have something intermittent in your prime circuit wiring. Either way, something in the prime circuit is at fault.
Last edited by Mr6spd; Sep 24, 2007 at 08:32 PM.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Remember, when you turn the key to the "ON" position but don't crank the engine, the pump will only run for 2-3 seconds.
If in that time the ECM doesn't detect the engine cranking, it shuts off the pump. The ECM looks for ignition pulses.
If the fuel pump relay is bad, the fuel pump should still energize once the oil pressure reaches 4 psi. Sort of a backup to the relay.
Jake
If in that time the ECM doesn't detect the engine cranking, it shuts off the pump. The ECM looks for ignition pulses.
If the fuel pump relay is bad, the fuel pump should still energize once the oil pressure reaches 4 psi. Sort of a backup to the relay.
Jake
Safety Car
Joined: Jul 2004
Posts: 3,845
Likes: 30
Remember, when you turn the key to the "ON" position but don't crank the engine, the pump will only run for 2-3 seconds.
If in that time the ECM doesn't detect the engine cranking, it shuts off the pump. The ECM looks for ignition pulses.
If the fuel pump relay is bad, the fuel pump should still energize once the oil pressure reaches 4 psi. Sort of a backup to the relay.
Jake
If in that time the ECM doesn't detect the engine cranking, it shuts off the pump. The ECM looks for ignition pulses.
If the fuel pump relay is bad, the fuel pump should still energize once the oil pressure reaches 4 psi. Sort of a backup to the relay.
Jake
