Fuel pump relay and gray wire leading to pump

Tiny
BRUCEJ455
  • MEMBER
  • 2004 CHEVROLET EXPRESS
  • 4.8L
  • V8
  • 2WD
  • AUTOMATIC
  • 320,000 MILES
Cannot get new fuel pump to run. Relay will not energize and gray wire has no bat on it. If power is put to gray wire back at frame rail near pump it will run and engine will start. Had no ground to terminal 35 of relay. Replaced PCM and got ground. Still have no bat to terminal 35. Have jumper-ed term 30 to 76 (wire that is supposed to run to fuel pump and pump is not energized). Checked ignition 1 and ignition 2 fuses and are okay. Read could be oil sw so replaced. Still will not energize fuel relay. Am stumped.
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Thursday, November 1st, 2018 AT 3:21 PM

13 Replies

Tiny
ASEMASTER6371
  • EXPERT
Good evening.

On the relay, 30 is powered by a fuse from the fuse block. It is shown in the diagram I sent. 30 is for the load side.

The control side ground comes from the PCM. When the key is turned on, it will power pin 85. Then after two seconds, it will shut off. It will send constant voltage cranking and running.

Verify those voltages for me.

Roy
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Thursday, November 1st, 2018 AT 3:35 PM
Tiny
BRUCEJ455
  • MEMBER
Roy the PCM is new so what you are telling me is PCM supplies both the ground and power to relay. If that is the case then I need to return PCM and get a refund or one that is good. Correct?
Bruce
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Thursday, November 1st, 2018 AT 5:29 PM
Tiny
ASEMASTER6371
  • EXPERT
If you look at the diagram, yes, the PCM controls the control side of the relay.

That is why you need to verify that voltage. If there is no voltage, then yes, the PCM is the issue.

Roy
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Friday, November 2nd, 2018 AT 1:17 AM
Tiny
DATADIGGER
  • MEMBER
  • 2004 CHEVROLET EXPRESS
  • 5.4L
  • 80,000 MILES
The van is parked in the driveway and hasn't been ran at all today and when Scott got home from work he walked by the van and heard a beeping from under the hood - so he looked to see what it was and he said it was coming from the fuel pump relay - what causes this problem and what needs to be done to repair and/or replace the problem
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Wednesday, November 7th, 2018 AT 5:46 PM (Merged)
Tiny
CARADIODOC
  • EXPERT
There's two common things to consider. First of all, if the battery is the original one, it has lost most of its capacity even though it may still be working. If the voltage has started dropping, some of the many computers will not go to "sleep" mode and will do weird things. GM has had a huge problem with their generators since they redesigned them for the '87 model year, and the main cause of the large number of repeat failures is a battery that is more than two years old. If your battery isn't that old, that likely is not the problem.

The second thing is there are a number of self-tests those computers run at various times, and some of them run after the engine has been off for awhile. One of those tests involves testing the fuel supply system for pinhole leaks, as in the infamous loose gas caps. You may be hearing one of those tests being run.

I don't know who Scott is. If he doesn't belong in your yard, you'd never have been made aware of the noise and you wouldn't be worried. If the noise doesn't stop and you start having other symptoms, that's the time to be concerned.
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Wednesday, November 7th, 2018 AT 5:46 PM (Merged)
Tiny
STEVEN TUCKER
  • MEMBER
  • 2007 CHEVROLET EXPRESS
Engine Mechanical problem
2007 Chevy Express V8 Two Wheel Drive Automatic

Van is not getting any fuel. Have checked all fuses and relays. Trying to narrow down the problem to determine if it is the fuel pump but not sure if any sensors could be the problem.
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Wednesday, November 7th, 2018 AT 5:46 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
Do you hear the fuel pump come On for a few secs if so check the fuel pressure if not recheck the fuel pump fuse and Fp relay
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Wednesday, November 7th, 2018 AT 5:46 PM (Merged)
Tiny
STEVEN TUCKER
  • MEMBER
I do not hear the fuel pump. I have checked the pressure and have none. Fuses and FP relay are good.
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Wednesday, November 7th, 2018 AT 5:46 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
Check for power at the fuel pump connector and the ground side of the circuit
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Wednesday, November 7th, 2018 AT 5:46 PM (Merged)
Tiny
STEVEN TUCKER
  • MEMBER
Should there be constant power there or just pulses and if power is there I would assume its the pump. If not are there any sensors that would prevent completing the circuit?
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Wednesday, November 7th, 2018 AT 5:46 PM (Merged)
Tiny
BJOHNSON8
  • MEMBER
  • 2000 CHEVROLET EXPRESS
  • V8
  • 2WD
  • AUTOMATIC
  • 120,000 MILES
We didnt have very strong fuel pressure to run the van so we replaced the fuel pump. But once we plugged the new one in it wouldnt even kick on. We were wondering if it could be an electrical problem somewhere? We checked all the fuses and the fuel pump relay and all seem to be working fine. Also we checked to see if we had any power to the pump with a test light but there was none at the pump
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Wednesday, November 7th, 2018 AT 5:46 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
If there's power for 2 secs and while crankibng -and still no fuel pressure check the fp ground circuit if okay replace the pump
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Wednesday, November 7th, 2018 AT 5:46 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
The problem could be the power feed between the relay and pump or it has a bad ground, possibly a bad new pump
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Wednesday, November 7th, 2018 AT 5:46 PM (Merged)

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