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2002 GMC Sierra wont start

Tiny
JJPARAMEDIC243
  • MEMBER
  • 2002 GMC SIERRA
  • V8
  • 4WD
  • AUTOMATIC
  • 143,000 MILES
Truck was running the other day while I was loading it when it died. It was very cold out and my tank was nearly empty so I thought it may have froze. Out it in garage and heated it up for several hours. It started but just for a couple of seconds then died, did this repeatedly til battery died. Thought maybe there was just to much water in the fuel so I added gas til tank was half full. Wouldn't start. Checked relay(removed and tested for click)checked voltage from relay PRIME terminal to ground voltage present when pump cycles on. No "whirring sound from pump and no pressure at manifold. Replaced fuel pump and filter still no start. Checked wiring harness, jumped relay prime to positive battery cable and tested voltage on grey wire on plug to fuel pump at pump-no voltage, good continuity on black wire to chassis ground. What am I missing? No power? I don't know what else to test. As a side note this truck had started very rough in cold weather for 4 or 5 years now with constant engine codes of lean right and left bank and engine misfire but learns it way out of it after about 10 minutes.
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Monday, January 17th, 2011 AT 4:37 AM

11 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
There is a primary and secondary fuel pump relay. The primary is in the under hood fuse block. The secondary is on the left side of the engine compartment on underhood fuse block bracket. Check both. I have to say, I'm a little confused. You mentioned "primary to ground voltage present when pump cycles on. No whirring sound from pump." Is that power present at the pump or only the at the relay? Also, have you checked the power supply wire for continunity? If you have power from the relay out, it should make it to the pump unless there is a break in the wire.

As far as the lean mixture, check the basics such as for vacuum leaks, if you have a scanner, live test the sensors to make sure they are staying with in.35V and.55V output. If they are out of that spec, they are bad. However, since both sides are lean, I feel a vacuum leak is the cause.
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Monday, January 17th, 2011 AT 4:58 AM
Tiny
JJPARAMEDIC243
  • MEMBER
  • 8 POSTS
The voltage test I was referring to was the relay circuit. My manual said to put a voltmeter on the relay PRIME terminal and chassis ground at the relay. Then turn the key and voltage should b present for 2 seconds or so. That test was good. Would that test confirm both relays r working? Also I only have a haynes manual it only shows a secondary relay for 6.0 L?Ill check for secondary relay and grey wire continuity. Thanks for the help so far!
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Monday, January 17th, 2011 AT 6:36 AM
Tiny
JJPARAMEDIC243
  • MEMBER
  • 8 POSTS
Found grey wire was broken back by tank resoldered all 4 wires at the end where it plugs into fuel pump checked continuity- have good ground and grey wire has continuity w with the slot in the relay receptacle that is the lower left corner if ur looking at it from the drivers side of the vehicle
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Tuesday, January 18th, 2011 AT 12:08 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
That all sounds good. There should be power there if it is coming from the relay unless there is an open in the power supply.
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Tuesday, January 18th, 2011 AT 2:33 AM
Tiny
JJPARAMEDIC243
  • MEMBER
  • 8 POSTS
Still no power to fuel pump
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Tuesday, January 18th, 2011 AT 3:17 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
Then there has to be a break in the wiring between the relay and the pump. If power is coming out of the relay but not getting to the plug for the pump, it has to be a broken wire. It could be internal and not seen.
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Tuesday, January 18th, 2011 AT 3:42 AM
Tiny
JJPARAMEDIC243
  • MEMBER
  • 8 POSTS
I'm still struggling here, I even pulled fuse block so I could check continuity from the beginning of the grey wire to the end, it was good at the back of the connector.(Did find a mouse net in my fuse block, but no chewed wires.) Grey wire actually runs from the relay Prime terminal, to the pump. The relay socket that got continuity with the grey wire on is actually the green/white wire that runs to the PCM. I did try a new relay to, and all fuses inside fuseblock and inside truck have been checked. Also is there a way to donate again?
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Tuesday, January 18th, 2011 AT 4:51 AM
Tiny
JJPARAMEDIC243
  • MEMBER
  • 8 POSTS
Could I put a wire in the PRIME terminal and attach it to the grey at the pump end that would effectively just bypass the grey wire right?
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Tuesday, January 18th, 2011 AT 4:55 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
There is no need to donate again. You could run a jumper to see if that takes care of the problem. Just make sure the wire gauge is equal to the one you are bypassing.
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Tuesday, January 18th, 2011 AT 5:33 AM
Tiny
JJPARAMEDIC243
  • MEMBER
  • 8 POSTS
Ahhh, a conclusion. So I went out this morning to try the jumper wire I suggested in the previous post. I put my ANALOG meter on the PRIME terminal and the chassis ground in the engine compartment. No power, or so I thought. I had it one the wrong scale! After correcting that and putting it on a scale where I could see 12 volts it tested fine. So I ran the jumper wire and kept the end( about 10 feet) with me in the engine compartment and metered it to the engine ground- 12 volts. I then took the end of the wire and metered it to the ground by the fuel tank-2 volts. Had power all along, just had meter on wrong scale for other testing, never observed the bad ground only that there was continuity present before. I had broken off the original grounding bolt when removing the tank for pump replacement and although I put the new ground bolt right next to the other hole location I guess I didn't clean the wires and surface good enough. Clean it all up with some 80 grit, fired right up. Always the simplest stuff. Thanks for taking the time to reply me.
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Wednesday, January 19th, 2011 AT 5:53 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
Honestly. That is the type of thing that would happen to me. I'm glad it's fixed. You take care of yourself and let us know in the future if you have questions.

Joe
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Thursday, January 20th, 2011 AT 4:02 PM

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