Fuel pump relay and oil pump sensor
Thread Starter
Cruising
Joined: Oct 2015
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From: Hamilton Waikato
Fuel pump relay and oil pump sensor
Hi there, I have an 89 C4 with a starting problem and I believe the oil pump sensor is faulty displaying 80psi on the display console.
Should the car still start with a faulty oil pump sensor if the relay is good?
Cheers
Should the car still start with a faulty oil pump sensor if the relay is good?
Cheers
Thread Starter
Cruising
Joined: Oct 2015
Posts: 12
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From: Hamilton Waikato
Cranking but not firing, and randomly dying without being able to re-start. It was possible to re-start after sitting for a while.
I notice the oil pressure displays 80psi when it doesn't fire.
I use to hear the pump prime and then it would fire and run for a bit then randomly die, and when I go to re-start I can hear the pump make a few faint clicks - cranks but doesn't fire.
Now I don't hear the pump prime and it won't fire.
I checked the injector resistance (cold) and they seem fine. I don't have any test wires to check the relay at the moment.
Hopefully, that makes sense.
I notice the oil pressure displays 80psi when it doesn't fire.
I use to hear the pump prime and then it would fire and run for a bit then randomly die, and when I go to re-start I can hear the pump make a few faint clicks - cranks but doesn't fire.
Now I don't hear the pump prime and it won't fire.
I checked the injector resistance (cold) and they seem fine. I don't have any test wires to check the relay at the moment.
Hopefully, that makes sense.
Team Owner
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From: Athens AL
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The oil pressure sender reading 80psi means either it is bad or the connector to it is bad, the pressure sending unit does not effect the fuel pump relay. You are confusing with the oil pressure switch, which sits right beside it on the back of the intake manifold, the switch has no effect on the dash pressure reading.
Apply 12V to Terminal G of the ALDL and see if the pump powers on at all, if not then the relay is suspect, then apply 12V to the pump directly at the gas tank, then suspect the wiring to the pump is likely bad, and pull the sending unit to inspect. They do appear to be wearing out as these cars hit their 30s. Your Helm FSM has the full procedure, so if you don't have one, you need one.
Apply 12V to Terminal G of the ALDL and see if the pump powers on at all, if not then the relay is suspect, then apply 12V to the pump directly at the gas tank, then suspect the wiring to the pump is likely bad, and pull the sending unit to inspect. They do appear to be wearing out as these cars hit their 30s. Your Helm FSM has the full procedure, so if you don't have one, you need one.
Last edited by vader86; Apr 24, 2020 at 10:41 AM.
Safety Car
Joined: May 2001
Posts: 4,759
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From: Fairfax Virginia
I would start at your battery and measure the voltage. Then go into your Corvette and measure the voltage at the fuse panel. They should be very close or identical, if not you have corrosion at the post where the Fusible links get their Power from.
My 1988 would crank but not start. I noticed that I had a serious voltage drop of close to 2 volts at the fuse panel. It was the post behind the battery under the side cover on the drivers side on my 1988 C4 Coupe. After cleaning the fuel pump primed and the radio started working. The fusible links supply battery power to most of the Corvette's systems. With the proper voltage everything works better.
This happens quite often on Corvettes from the Rust belt states. Mine came from New Jersey and was a real mess. Bubba tried to crimp a couple important wires and made bad crimps which were responsible for intermittent issues. It took a while to De-Bubba-ize the Corvette than I expected.
My 1988 would crank but not start. I noticed that I had a serious voltage drop of close to 2 volts at the fuse panel. It was the post behind the battery under the side cover on the drivers side on my 1988 C4 Coupe. After cleaning the fuel pump primed and the radio started working. The fusible links supply battery power to most of the Corvette's systems. With the proper voltage everything works better.
This happens quite often on Corvettes from the Rust belt states. Mine came from New Jersey and was a real mess. Bubba tried to crimp a couple important wires and made bad crimps which were responsible for intermittent issues. It took a while to De-Bubba-ize the Corvette than I expected.
Thread Starter
Cruising
Joined: Oct 2015
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From: Hamilton Waikato
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Thread Starter
Cruising
Joined: Oct 2015
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From: Hamilton Waikato
Today I had a quick look at the Schrader valve on the rail and it was only finger tight. So far after tightening the valve there have been no further issues but I still need to check the pressure.
The valve has an aluminum washer with what looks to be an o ring. Can anyone confirm how it's sealed?
Cheers
The valve has an aluminum washer with what looks to be an o ring. Can anyone confirm how it's sealed?
Cheers