fuel pump???

mantis · 06-24-2008, 04:21 PM

Hey guys.I am having a problem with my '99 sierra 1500 4.8LT.It started last summer.I cleaned the ground to the frame and it ran great for about 6 months or so,Then acted up again.Cleaned the ground again and it ran fine for a little while.Pulled out of the driveway and it stalled out.Pushed it back in the driveway and tried it again and nothing.About 5 hrs later I tried it again and it started right up. I tried it again in the morning and it started up.So I did a pressure test it read about 50 PSI. It was running fine and than started to loose pressure,droped to about 10 PSI and stalled out. after about another 5 hrs I tried it again and it ran for about 6 minutes and then lost pressur again. Switched relays no differance.Would this be some kind of vapor lock? I took the gas cap off and it still acts the same.I am getting power to the pump but nothing.If I go direct to the pump it will start

.thats where I am now, and I don't have much hair left to pull out

mantis · 06-24-2008, 04:29 PM

UPDATE I disconnected the fuel pump in the truck and connected am other pump that I have and know that works and that one will not work either

Any ideas

og25 · 06-24-2008, 04:44 PM

Hey mantis, Did you replace the fuel filter? Sometimes the debris in the filter settles when the truck isn't running, then you start it and the fuel pressure moves the debris around and clogs up the line.

mantis · 06-24-2008, 04:49 PM

Quote:

Originally Posted by og25

Hey mantis, Did you replace the fuel filter? Sometimes the debris in the filter settles when the truck isn't running, then you start it and the fuel pressure moves the debris around and clogs up the line.

I replaced it in August or September.I don't think it would have cloged that quickly,but I could be wrong

og25 · 06-24-2008, 04:53 PM

That's all I have right now, but I'll keep thinking! Let us know if you get it fixed! Good luck!

mantis · 06-24-2008, 05:00 PM

Quote:

Originally Posted by og25

That's all I have right now, but I'll keep thinking! Let us know if you get it fixed! Good luck!

Thanks og. I'm at the same place I would say it might be the filter but the old oump wount work either and that isn't even in the tank. plug it in and nothing it won't even kick on

og25 · 06-24-2008, 05:46 PM

ok. the truck starts and then loses prresure. Are you losing power to the pump or just pressure?

leolkfrm · 06-24-2008, 06:36 PM

hows the fuel pump pressure switch?

mantis · 06-24-2008, 06:51 PM

Quote:

Originally Posted by leolkfrm

hows the fuel pump pressure switch?

Where can I find that?

og25 · 06-24-2008, 07:16 PM

hey mantis, On my 96 the fuel pump/oil pressure switch is by the distributor on the driver side. That's a 454 I guess yours is the same.

06-24-2008, 04:21 PM	#1 (permalink)
mantis Full Member Join Date: Jun 2008 Posts: 32	fuel pump??? Hey guys.I am having a problem with my '99 sierra 1500 4.8LT.It started last summer.I cleaned the ground to the frame and it ran great for about 6 months or so,Then acted up again.Cleaned the ground again and it ran fine for a little while.Pulled out of the driveway and it stalled out.Pushed it back in the driveway and tried it again and nothing.About 5 hrs later I tried it again and it started right up. I tried it again in the morning and it started up.So I did a pressure test it read about 50 PSI. It was running fine and than started to loose pressure,droped to about 10 PSI and stalled out. after about another 5 hrs I tried it again and it ran for about 6 minutes and then lost pressur again. Switched relays no differance.Would this be some kind of vapor lock? I took the gas cap off and it still acts the same.I am getting power to the pump but nothing.If I go direct to the pump it will start .thats where I am now, and I don't have much hair left to pull out

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06-24-2008, 04:29 PM	#2 (permalink)
mantis Full Member Join Date: Jun 2008 Posts: 32	UPDATE I disconnected the fuel pump in the truck and connected am other pump that I have and know that works and that one will not work either Any ideas

06-24-2008, 04:44 PM	#3 (permalink)
og25 Full Member Join Date: Jun 2008 Posts: 23	Hey mantis, Did you replace the fuel filter? Sometimes the debris in the filter settles when the truck isn't running, then you start it and the fuel pressure moves the debris around and clogs up the line.

06-24-2008, 04:53 PM	#5 (permalink)
og25 Full Member Join Date: Jun 2008 Posts: 23	That's all I have right now, but I'll keep thinking! Let us know if you get it fixed! Good luck!

06-24-2008, 05:46 PM	#7 (permalink)
og25 Full Member Join Date: Jun 2008 Posts: 23	ok. the truck starts and then loses prresure. Are you losing power to the pump or just pressure?

06-24-2008, 06:36 PM	#8 (permalink)
leolkfrm Senior Member Join Date: Mar 2008 Location: N.Y. Posts: 473	hows the fuel pump pressure switch?

06-24-2008, 07:16 PM	#10 (permalink)
og25 Full Member Join Date: Jun 2008 Posts: 23	hey mantis, On my 96 the fuel pump/oil pressure switch is by the distributor on the driver side. That's a 454 I guess yours is the same.