Strike3

The car is a 91 L98. I know it is under the dash somewhere. I can't remember if it is the drivers or passengers side, or specifically which one it is.

A diagram or picture would be very helpful. I am stuck about a thousand miles from my shop, tools and service manuals.

Thanks!

C409

..... On my '87 its on the firewall between the wiper motor and the brake booster .......

GKK

The "91" fuel pump relay is on the passenger side dash under the plastic hush panel where the floor courtesy light is attached to.

After removing the hush panel, (if you're tall you might have to remove the seat) look up towards the rear of the car and you'll see a panel of 5 relays mounted on the dash frame. The fuel pump relay is the middle one if I remember correctly.

It'll be very close to your eye's and I could barely focus on them. Use a flashlight and you'll eventually see it.

stoydido

the panel has three on passenger side, a gap, then two towards other side. the fuel relay is the third from the right side, or pass side.

if you want to verify if it works, if the fuel pump comes on for 2 secs when key is turned "on" the relay works.
the FP is pretty quiet, so you may have to stand at the gas tank while someone turns key, or you will hear the ABS under the storage tray and think it is pump.

Joe B.

I believe those relays are the same and one is for the interior lights, so you could switch them to get back on the road if the problem is a bad fuel pump relay.

stoydido

or use the backup which is more or less automatic, the oil pressure switch. takes more crank time but the engine will run.

Strike3

I don't understand this one,,,,,,,,,,. what about the oil pressure switch? Explain please.

Joe B.

According to the '91 FSM, if the fuel pump relay fails, the fuel pump can be turned on by the oil pressure sensor/switch, also a code 54 will be set. Long cranking times may result because oil pressure needs to be 4psi before the oil pressure sensor/switch turns "on" the fuel pump.
So, yes your car should start with a bad fuel pump relay. You just have to crank it long enough for oil pressure to reach 4psi, then the oil pressure sensor/ switch will turn the pump "on".
(This is also a safety feature to shut the engine if oil pressure drops below that level)

GKK

The oil pressure switch will provide 12 volts Directly to the fuel pump after it senses 4psi of oil pressure. It'll power the fuel pump if the fuel relay ever fails.

A little longer cranking time usually indicates the fuel relay has gone bad.

joe paco

yep; fsm page 8a-2--6. red #458 goes to fuse but not relay, a parallel circuit. as someone said, test for fp relay by turning key on, have someone listen at the tank for the pump. you may hear it clicking under dash if you remove fuse.

on the 91 it is HIGHLY unlikely that the oil switch plug had been disconnected. so engine should run.