Fuel '91 4-cyl swap fuel pump stopped working suddenly.

Haste347

Member
Oct 6, 2020
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Houston
Hello! I've got my hands (about a year ago) on a '91 notch that is a converted 4-cylinder. It has been running great since I got it and was out for a drive today. It was running fine on the way to a friends house, but would not crank up when I went to leave. My fuel gauge wasn't registering fuel pressure, and I couldn't hear my fuel pump as I normally do.

This notch came with a long list of goodies, one of them was an aftermarket fuel system. The factory fuel lines were bypassed and I found an aftermarket pump/pickup (quantum e85) in the tank when I dropped it. Oddly enough, I found constant voltage at the pump connector despite the key position. I started pulling things off the front starter solenoid post until voltage dropped. What was feeding the voltage was a blue/brown pair of cables (pictured below). The color of wire feeding the voltage to the pump was a yellow/black pair. These seem to be factory wires and the factory harness above the fuel tank.
Another oddity is that there is no fuel pump relay under the drivers seat even though there is the harness for it under the seat, the relay just isn't there.

My initial guess is that there is a relay, just not where I am expecting it to be (under the driver's seat), and it has gone bad.

1) Am I correct in presuming there should be no voltage to the pump when the key is off?
2) Would the fuel pump relay be in a different spot since it's a 4-cylinder conversion?
3) Are the Quantum pumps any good? I may just get an Aeromotive drop-in replacement if the Quantum's aren't reliable.

Thanks for any info/advice/troubleshooting help!


Fuel pump at front solenoid post.jpg
Connector above tank.jpg
 
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General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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polk county florida
Do you have a scanner and the test plug under the hood? On V8 cars there is a plug there that sends power to the fuel pump when jumped. You can find more info on this in the 'cranks but no start checklist'
 

KRUISR

5 Year Member
Apr 16, 2015
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On '91 V8's the fuel pump relay is in the engine compartment, passenger side near where the MAF is.

When the car is off, the pump should not have voltage and should not run.

I had issue with my pump staying on and it turned out to be the connector in the driver kick panel (by your toe). The factory fuel pump circuit runs through there.
 

Haste347

Member
Oct 6, 2020
16
3
13
44
Houston
On '91 V8's the fuel pump relay is in the engine compartment, passenger side near where the MAF is.

When the car is off, the pump should not have voltage and should not run.

I had issue with my pump staying on and it turned out to be the connector in the driver kick panel (by your toe). The factory fuel pump circuit runs through there.
The engine bay had some panels installed to cover up the holes and much of the wiring/relays were relocated.
Would you mind giving a bit of description on the connector in the kick panel (if it's not obvious). How was yours defective, was it just some corrosion that needed to be cleaned up?

Thanks for the info!
 

KRUISR

5 Year Member
Apr 16, 2015
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The connector is a 12 pin (2 rows of 6) - There are 2 such connectors in the area. Find the fuel pump relay and see what colours are coming out of it. Find these colours in the 12 pin and you have the right one. This issue I had was the female pin had opened up a bit so that it did not make firm contact with the male pin. When connected the male pin would loose contact and shut off the pump. Wiggle the connector and it would work, bump kick panel while driving with your foot and out it would go again.

I took a small screwdriver (like eyeglasses small) and pried the sides of the female connector to make it smaller. Now male pin maintains contact. All good.