2002 GMC Sierra wont start

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.

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!

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

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.

Still no power to fuel pump

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.

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?

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?

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.

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.

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