New fuel pump and relay and no power to pump

Tiny
GREENPHANTOM311
  • MEMBER
  • 1997 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 270,000 MILES
Just replaced the transmission in my truck. Got everything hooked up and went to start it. Heard the fuel pump kick on and off while I turned the key over. Truck started with a jump and ran for approximately 3 minutes then just shut off. Tried to start it again and now nothing coming from the fuel pump. No hum or noise whatsoever. Is there something that i'm overlooking that would cause the fuel pump to just stop in mid idle and not engage again? I'm about to my whits ends with this truck.
Monday, April 6th, 2020 AT 7:01 PM

30 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Good morning,

First, go over your work with the transmission. I believe there is a ground wire on one of the bell housing bolts at the top. Make sure it is connected and tight.

I attached a wiring diagram for you to view. You will need a test light or voltmeter to do some wiring tests to find the failure.

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

The gray wire is what goes to the fuel pump. Test that for power when you turn on the key. It will run the pump for 2 seconds and shut off.

Roy
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Tuesday, April 7th, 2020 AT 4:31 AM
Tiny
MOTOR MASTER
  • MECHANIC
  • 279 POSTS
Hello my name is Dave.

First thing I would recommend is to see if you have any codes stored. One thing I suspect when a transmission has been replaced on these vehicles is the oil pressure/fuel pump switch on the back of the engine, I have seen the wires get pinched on reinstall and cause the problem you have described. The switch is right behind the intake on the driver's side, check and make sure those wires didn't get pinched or damaged.

If you can check on those wires and let us know the results we will be glad to assist you further if needed, please keep us up to date on your progress and thank you for using 2CarPros!
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Tuesday, April 7th, 2020 AT 4:36 AM
Tiny
GREENPHANTOM311
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  • 16 POSTS
I actually had to replace the whole sensor because I noticed when I took the other transmission out it was completely broke.
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Tuesday, April 7th, 2020 AT 1:45 PM
Tiny
ASEMASTER6371
  • MECHANIC
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Did you check the wires at the relay for power?

The oil pressure sensor has no involvement in the fuel pump circuit.

Did you check the ground wires?

Roy
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Tuesday, April 7th, 2020 AT 1:56 PM
Tiny
GREENPHANTOM311
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  • 16 POSTS
When I hook the test light up to the negative side of the battery and touched parts in where the relay was I do have power going to some part of the relay but as far as anything going past that I have no idea. The thing is is that when I put the transmission in it I had to jump the truck and it started and ran fine for about 3 to 5 minutes at which I forgot time the fuel pump just shut off and stopped working.
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Tuesday, April 7th, 2020 AT 1:59 PM
Tiny
ASEMASTER6371
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Yes, I read that.

Let me know when you can do pinpoint testing and I will walk you through it.

Roy
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Tuesday, April 7th, 2020 AT 2:02 PM
Tiny
GREENPHANTOM311
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Not really sure what I would need to do it. All I have is a test light with a 1 foot cord.
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Tuesday, April 7th, 2020 AT 5:33 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
You need to go to the relay and remove it. With the key on, you should have 1 terminal that has power.

Then test the other terminals. Have someone in the truck and turn the key to on. 1 of the other terminals should have power for 2 seconds and shut off. That is normal.

Do these checks and let me know.

Roy
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Tuesday, April 7th, 2020 AT 5:38 PM
Tiny
GREENPHANTOM311
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Okay. Should the test light be hooked to the negative side of the battery? When it comes to electric and wires I'm a little clueless.
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Tuesday, April 7th, 2020 AT 6:21 PM
Tiny
ASEMASTER6371
  • MECHANIC
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Yes, black lead to the negative side of the battery.

I attached a guide for using the test light for you.

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

Roy
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Wednesday, April 8th, 2020 AT 3:51 AM
Tiny
GREENPHANTOM311
  • MEMBER
  • 16 POSTS
I was able to hook the test light off. I do have one that comes on when the key is off and then there is one that comes on when the key is turned on and it is a separate one.
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Wednesday, April 8th, 2020 AT 12:59 PM
Tiny
ASEMASTER6371
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Okay, good.

When you turn on the key, can you feel the relay energize and then release?

Roy
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Wednesday, April 8th, 2020 AT 1:05 PM
Tiny
GREENPHANTOM311
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  • 16 POSTS
I took the relay to work and put them in our work truck which has the same fuel relay and it worked in the work truck.
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Wednesday, April 8th, 2020 AT 2:07 PM
Tiny
ASEMASTER6371
  • MECHANIC
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That is not what we are doing. We are testing voltages, not testing the relay.

Please do the checks I requested.

Roy
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Wednesday, April 8th, 2020 AT 2:13 PM
Tiny
GREENPHANTOM311
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  • 16 POSTS
Okay. With the negative side hooked up and no key in the ignition or on I have one light where the relay is supposed to be with the test light.
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Wednesday, April 8th, 2020 AT 4:47 PM
Tiny
GREENPHANTOM311
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  • 16 POSTS
I can also put the relay in and turn the key over and feel the relay click and then click again after a few seconds.
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Wednesday, April 8th, 2020 AT 5:14 PM
Tiny
ASEMASTER6371
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Okay, that is good. That means it is being activated by the ECM.

Now you need to go to the fuel tank and test the gray wire for power when you turn the key to on.

If you have power and the fuel pump does not work, you need a pump.

If you do not have power, then there is a wiring issue between the relay and the fuel pump.

Roy
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Wednesday, April 8th, 2020 AT 5:18 PM
Tiny
GREENPHANTOM311
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Okay, does the test light need to be hooked up to the negative side of the battery or can it just be hooked up to a ground on the bottom of the frame?
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Wednesday, April 8th, 2020 AT 5:20 PM
Tiny
ASEMASTER6371
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Just to a good body ground. There are many places to hook it to. Just make sure it is a good clean contact.

Roy
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Wednesday, April 8th, 2020 AT 5:33 PM
Tiny
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When I put the key in the ignition and turn it on there is no power coming to the gray wire, but there is power going to the purple wire which is the one that is in the middle of the three.
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Wednesday, April 8th, 2020 AT 5:46 PM

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