90c4convetible

Can anyone tell me the exact location of the fuel pump relay in a 90 convertible c4?

oldalaskaman

I dont have a 90 and i may be wrong, but doing a search says its to the right of the winshield wiper motor on one and on the other its behind the i/p. sorry I cant be more clear

90c4convetible

Thanks I am having trouble finding the locations, I have some wiring diagrams but they dont have anything about where it is located.

Hooked on Vettes

Fuel Pump Relay 1 is on the passenger side front edge of the dash.

Fuel Pump Relay 2 is located below the dash cluster and is only used by the ZR1.

You need to remove the plastic panel with the foot well lamp
to get to Fuel Pump Relay 1.

All the relays in that area are the same so you can swap them around.

90c4convetible

Thanks for the diagrams they were very useful. I checked fuel pump relay #1 and it was fine. I did not see that you had said relay #2 was only used by zr1 but there was a relay in that spot under the instrument panel and it is shorted. I am not sure if that is the problem, but as soon as the parts stores open back up tomorrow I will be there to get another relay to confirm whether or not that is the problem. Again thanks for all the help!!!!!!!!

Hooked on Vettes

The ECM applies 12 volts to the Dark Green/White wire to turn on the
fuel pump relay.

You didn't say what your problem is. If the fuel pump runs
with the ignition off, it could be the oil pressure switch/sender behind the
distributor on the driverside is bad.



It has two functions. It is an oil pressure sender and it also
has contacts that close if the oil pressure is above 4 psi. When the
contacts close, 12 volts from an Orange wire (hot at all times) passes
through the switch and provides 12 volts to a Red wire that provides
12 volts to the fuel pump fuse and the fuel pump will run. This is a
backup source in case the Fuel Pump relay fails.

If the switch fails in the closed position, the fuel pump will run
all the time. Current path is in Blue for the oil pressure switch.

90c4convetible

My problem is the fuel pump isnt priming like it did before it was put into storage. This is causing the car not to start. I was hoping it would be the relay because that is much easier to get to than the fuel pump.

Hooked on Vettes

If the ECM can't control the fuel pump relay
if you keep cranking the engine, eventually
4 psi of oil pressure will close the oil switch
and the fuel pump will get 12 volts from the
oil switch.

It just takes extended cranking time before
the engine will start.

Also under the hood is a wiring harness near the power
brake booster. There is a single Red wire with a female
spade lug. If you apply 12 volts from the Battery
to this terminal the fuel pump should run all
the time even with the ignition off.

If the fuel pump doesn't run most likely the fuel pump is bad.

90c4convetible

Well the fuel pump is bad and I am getting one to replace it.