Mechanics

FUEL PUMP PROBLEM

2002 GMC Sierra

Electrical problem
2002 GMC Sierra V8 Four Wheel Drive Automatic 192, 00 miles

I CHANGED THE FUEL PUMP IN MY SON'S TRUCK BECAUSE IT WOULDN'T RUN. BEFORE I DID THIS, I CHECKED THE FUEL PUMP RELAY & ECM-B FUSE.
THEY WERE GOOD.
THE REASON I SUSPECTED FUEL PUMP IS BECAUSE I COULDN'T HEAR THE FUEL PUMP CYCLE WHEN WE WERE TRYING TO START THE TRUCK
AFTER CHANGING THE FUEL PUMP, THE TRUCK STILL WON'T RUN. I WENT BACK & CHECKED THE RELAY & ECM-B FUSE AGAIN.
THAT'S WHEN I DISCOVERED THAT THERE IS NO POWER TO THE FUEL PUMP RELAY.
THE FUEL PUMP WILL CYCLE FOR A VERY SHORT TIME, (LESS THAN A SECOND) WHEN THE IGNITION IS FIRST TURNED ON.
THE OIL PAN GASKET WAS REPLACED ABOUT A WEEK PRIOR TO HAVING THIS PROBLEM, SO I'M WONDERING IF THE OIL LEVEL SENSOR COULD HAVE BEEN DAMAGED DURING THE PROCESS.
(JUST A GUESS) AFTER THE OIL PAN GASKET WAS REPLACED, WE DROVE THE TRUCK HOME & IT WAS NOT DRIVEN AGAIN UNTIL WE TRIED TO START IT & DISCOVERED THIS PROBLEM.
THE TRUCK IS A 2500HD WITH THE 8.1 ENGINE.
Avatar
Mrblackwell
July 27, 2010.



Hi
ECMB 1 does power up relay are you using a volt meter to test voltage at fuse and across? Power origantes at small red wire off battery to fuse box. Make voltage readings at fuse box
Let me know
Thanks for donate

Docfixit
Jul 28, 2010.
I used a test light because I didn't have a volt meter with me at the time.
There is power on both sides of the ECMB-1 fuse, but I don't know what the voltage is.

Tiny
Mrblackwell
Jul 28, 2010.
Need meter tests light will light on little voltage and AMPS.
If fuse is powered then must be fault in wiring from fuse to relay

Docfixit
Jul 28, 2010.
Ok. I will check when I get home & see what the voltage is.

Tiny
Mrblackwell
Jul 28, 2010.
Haven't had a chance to check with volt meter yeat, but just out of curiosity, where is the pcm located?

Tiny
Mrblackwell
Jul 30, 2010.
Underhood


http://www.2carpros.com/forum/automotive_pictures/198357_Graphic_539.jpg


Docfixit
Jul 31, 2010.
Ok, here's where I'm at. Ended up taking the truck to GMC dealer. They diagnosed as a bad PCM.
I purchased a used PCM & took it to them (I actually put it in while I was there) & they reprogrammed it later that day.
After doing that, it still won't run. The tech says that before the PCM swap, it had fuel pressure, but the PCM wasn't communicating.
After the PCM swap, it is communicating, but now has no fuel pressure.
I went to the dealer & talked to the tech & he wanted to spray some carb cleaner to see if it would run, I guess he was thinking that the aftermarket pump I had put in it had maybe gone bad.
Sprayed it with the carb cleaner & it still did not run.
Just out of curiosity, I looked at his TECH-2 & now there is no communication with the PCM again.

Tiny
Mrblackwell
Aug 4, 2010.
Know this will sound to simple but has the oil level switch in right side oil pan been checked? Story began with oil pan gasket tehn no start

Docfixit
Aug 5, 2010.
No, it hasn't been checked. I have the truck back from the dealer now. Didn't want to keep paying them to guess what was wrong.
What's the procedure for testing the oil level sensor?

Tiny
Mrblackwell
Aug 5, 2010.