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Bad connection to fuel pump

Tiny
DANE JUSTUS
  • MEMBER
  • 2001 CHEVROLET SILVERADO
  • 4.3L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 188,000 MILES
Backstory. In January my truck shut off while idling. After a tow and some fiddling it was the fuel pump that was the issue. It was replaced, along with filters and a rebuild of the throttle body. Ran better than ever.

Last Thursday. Truck got me home fine, had a tear in the passenger tire, fun. Woke up for work, she would not start. All accessories were fine, battery was fine, truck would not start. She would crank, but not fire. After checking fuses, relays, throttle body, battery, it was found that there was no pressure in the fuel rail. After more electrical checking the tank was dropped, the pump was replaced and she is now in the same situation. Still no fuel at the rail. So it seems there is no power to the pump.

Today. Rechecked fuses and relays. Same no start condition. No codes running. Unhooked negative at battery, let sit for ten minutes. Reconnected. Same no start. Have battery unhooked currently. Wondering if it is PCM, a random faulty ground somewhere, the harness to the fuel pump, or possibly some easier solution I am not seeing as I am now focused on fuel delivery. Please help. I have fallen and I cannot get up.

-Dane
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Tuesday, June 6th, 2017 AT 3:59 PM

7 Replies

Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
Is your security light on? If so, take your key to the dealer and have it tested. The security systems (aka passlock) in these trucks can cause a no start situation like yours.

You might want to see TSB 01-08-56-002A

http://workshop-manuals.com/gmc/k_yukon/denali_4wd/v8-5.7l_vin_r/accessories_and_optional_equipment/antitheft_and_alarm_systems/security_lamp/indicator/component_information/technical_service_bulletins/all_technical_service_bulletins_for_security_lamp/indicator/01-08-56-002a/jun/01/security_system_lamp_on/dtc_b2960_set/
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Tuesday, June 6th, 2017 AT 7:13 PM
Tiny
DANE JUSTUS
  • MEMBER
  • 4 POSTS
No. No security light.
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Tuesday, June 6th, 2017 AT 7:33 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,573 POSTS
First, check the pump fuse (ECM B 20 amp), next test the pump relay, they like to get hot and melt the interior of the socket, when they cool off the plastic hardens and you get no power to the pump.
There is a gray wire that feeds power to the pump from terminal 87 on the relay. Connect a jumper from there to battery positive and the pump should turn on. If it does the power and ground feeds to the pump are okay and the truck should start. That would mean the issue is the relay/socket. It is ground (right front of the engine) or the power feed to the relay from the PCM. To test that take a test light. Connect one end to ground and probe the pump relay socket. Key on engine off you should have power to one terminal (30). Turn on the key on and you should find the pump prime power signal on terminal 85 for two seconds. If that is there then the wire to the PCM is okay.

If you can feel the relay click on for the two seconds but the pump does not power on, the relay is probable bad.
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Tuesday, June 6th, 2017 AT 11:35 PM
Tiny
DANE JUSTUS
  • MEMBER
  • 4 POSTS
Checked passlock cable. Held it down multiple ways. Still no start.

Jumped the relay sockets. The relays physically are backwards from the diagram. So I jumped both possible 87 locations. Still no start. I had verified proper voltage at jump lead.

I am believing the problem lay somewhere in the wiring harness, which has been spliced and rewrapped before. I will prepare to lift the truck and get to the pump/harness.

Thoughts?

-Dane
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Thursday, June 8th, 2017 AT 11:28 AM
Tiny
DANE JUSTUS
  • MEMBER
  • 4 POSTS
Lifted truck. Got to splice. Found this burn. K. We have the culprit, but why? I do not want to have to come back to this. I will check the new fuel pump box see if it has a new lead. I want to say the gauge was smaller. Will need to check.

Thoughts on the reason and how to alleviate this in the future?

Thanks.

-Dane
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Thursday, June 8th, 2017 AT 12:48 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Not to be a smart ass but it looks like it wasn't done right to begin with, put a solder joint on both wires and use shrink wrap around it, maybe two shrink wraps. It looks like I f it's shrink wrap it may be some really cheap stuff. Then check the ground and see how may amps pump is drawing as it may be drawing to many. Some of these trucks the pump was bad and a new harness had to be installed about a foot back because of poor connection. Normally they came with the harness and the connection was changed.
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Thursday, June 8th, 2017 AT 1:57 PM
Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
As HMAC stated, these trucks do have issues with the fuel pumps and their wiring. I've had 2 blazers (same fuel systems along with most other mechanical) and I've had to replace both fuel pumps. And the current one is having issues with the gauge sending unit (probably the wiring).

As far as a suggestion on how to fix that wire, I'd say trace it to the other end and replace the whole thing with a heavier gage wire.
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Thursday, June 8th, 2017 AT 5:26 PM

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