New fuel pump not working

MARVELOUSDRUMMER

MEMBER
1991 FORD PROBE
2.2L
4 CYL
2WD
MANUAL
250,000 MILES

On the way back from a doctor's appointment, my car stopped getting gas to the engine. The gas pedal would just go to the floor. The same way as if you ran out of gas. So, after getting the car towed home, I started diagnosing the problem. I came to the conclusion that the fuel pump had gone bad because you could not hear it priming. I bought a new pump, installed it, and still nothing. Since then, I have also replaced the relay and all fuses associated with the fuel system. Still nothing. I hotwired the new fuel pump to the battery to see if maybe the new fuel pump could be faulty, but it worked great. I'm now at a loss. Any help would be appreciated, thank you!

I should also mention that the inertia switch has been checked and the relay clicks when the key is turned.

3 Replies

BORIS K

MECHANIC
799 POSTS

Hello,

It looks like either the fuel pump is not getting 12V feed from the relay or the ground is not being switched by the inertia switch.

When you supplied the fuel pump with external 12V, did you only supply this to the white/yellow wire or did you also supply a ground to the white/red wire ?

See partial wiring diagram attached.

As you can hear the fuel pump relay click this indicates that the control, switch on side is working. We do not know is the switched side is working. Please check first that fuse 3 in the interior fuse block is in order and that it is supplied with 12V with ignition on. This can be done by either using a test light or multi meter.

If the fuse tests okay, then next please check that you get full battery voltage a the white/yellow wire at the fuel pump. This can only be done with ignition on but keep in mind that the fuel pump relay will only stay energized for 2-3 seconds without the engine running. So, you will need to cycle the ignition off/on and then immediately check the voltage at the fuel pump terminal

How to use a multi meter.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

How to use a test light.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

How to test a fuse.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

How to test a relay.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Please let us know how you get along.

Cheers, Boris

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Friday, January 21st, 2022 AT 1:54 AM

MARVELOUSDRUMMER

MEMBER
2 POSTS

Hello,

Thank you for replying so quickly. I checked fuse 3 today and it's getting 12V with the ignition on. However, the white/yellow wire at the fuel pump is getting 0V with the ignition on. I tested this multiple times. What are my next steps in solving this?

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Friday, January 21st, 2022 AT 1:25 PM

JACOBANDNICKOLAS

MECHANIC
109,758 POSTS

Hi,

I noticed it has been a couple of days since you have been contacted. When you checked for power at the pump, did you have a helper cycle the key from off to on? With the engine not running, you will get a short period of time for the pump to pressurize. Then, the power won't return until the engine starts.

If the relay and inertia switch are good, then there is a chance of an open circuit in the wire to the pump. Have you checked that wire from end to end for continuity?

https://www.2carpros.com/articles/how-to-check-wiring

Let me know.

Take care,

Joe

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Sunday, January 23rd, 2022 AT 5:09 PM