Bad fuel Pump? (Solved)

[WestCoastie]

(Edit) Solved, new fuel pump fixed the issue.

(Edit… to the Edit) A week went by of normal starting. Then the hard start acted up again. Only thing I hadn’t replaced is the cam sensor, it tested ok. Replaced it with GM genuine cam sensor and no more problems.


2003 GMC Yukon XL 1500 5.3

Back Story:

1. Engine spun a bearing
2. Sat outside for 6 months or so before got around to rebuild
3. After rebuild experienced hard starts (would sometimes fire right up, other times I had to crank a couple times before it finally would start up). But once it was running it seemed to run just fine.

I chocked up the issue to an electrical gremlin. As I had a couple to figure out after truck sat for so long. Eventually I fixed everything besides the hard starting (and 4x4, but that’s a whole other issue).

A week ago (right before heavy snow started falling) the truck just refused to start altogether.

Finally got a test kit to measure fuel pressure. When I initially put it on there was no pressure. I jumped the fuel pump and got up to about 50psi. After removing power, pressure fell to about 40 and slowly started falling.

I only jumped the fuel pump relay because it was easier, not because the key won’t activate it.

Everything about this screams fuel pump to me. But the fuel pump was replaced at 30k miles (about 110k in it now).

Im curious what everyone thinks.

Thanks!

 

[OR VietVet]

Sounds like bleeding off fuel pressure and that could be the fuel pump or injector(s) or line leak or.....etc.

 

[Trey Hardy]

2003 GMC Yukon XL 1500 5.3

Back Story:

1. Engine spun a bearing
2. Sat outside for 6 months or so before got around to rebuild
3. After rebuild experienced hard starts (would sometimes fire right up, other times I had to crank a couple times before it finally would start up). But once it was running it seemed to run just fine.

I chocked up the issue to an electrical gremlin. As I had a couple to figure out after truck sat for so long. Eventually I fixed everything besides the hard starting (and 4x4, but that’s a whole other issue).

A week ago (right before heavy snow started falling) the truck just refused to start altogether.

Finally got a test kit to measure fuel pressure. When I initially put it on there was no pressure. I jumped the fuel pump and got up to about 50psi. After removing power, pressure fell to about 40 and slowly started falling.

I only jumped the fuel pump relay because it was easier, not because the key won’t activate it.

Everything about this screams fuel pump to me. But the fuel pump was replaced at 30k miles (about 110k in it now).

Im curious what everyone thinks.

Thanks!

Sounds like the pump to me. No fuses blown correct?

 

[WestCoastie]

Sounds like bleeding off fuel pressure and that could be the fuel pump or injector(s) or line leak or.....etc.

I dont see any signs of leaking outside the system. Nothing coming out exhaust as if flooding from leaky injector(s). I figure if injectors were leaking I would still at least get a bit of a start.

 

[WestCoastie]

Sounds like the pump to me. No fuses blown correct?

Correct none blown, and due to other electrical issues almost all grounds have been found and cleaned up.

 

[OR VietVet]

If you don't know the quality of the fuel pump, then yes, it could be. Make sure you know if is flex fuel or not. Different pumps. Also, different pressures.

 

[WestCoastie]

If you don't know the quality of the fuel pump, then yes, it could be. Make sure you know if is flex fuel or not. Different pumps. Also, different pressures.

Mine is flex fuel. Thanks for the tip

 

[OR VietVet]

More Information for DELPHI FG0811

 

[Trey Hardy]

Correct none blown, and due to other electrical issues almost all grounds have been found and cleaned up

If you don’t know for sure it was a quality pump I’d put a good one in there personally but it could be as simple as a relay?
I said that about the fuses cause a buddy of mine went to some new shop to have his fuel pump fixed and it still wouldn’t run… come to find out the fuse was blown lol but now since he cheaped out on the fuel pump the gauge don’t work anymore so he’s got to go back into it again to get that straight or put the stock pump back in the truck

 

[Fless]

See the post below for specific fuel pressure test and specs. Replace the fuel pump relay just to rule it out; maybe test with the old one and again with a new one.

The Flex Fuel system on your year will have an inline fuel filter on the driver's side frame rail (near the alcohol sensor); consider replacing it if the age is unknown.

Fuel delivery?

Hello all I have a 2003 Yukon Denali 6.0 with 170k miles. Purchased about 6 months ago I’ve currently replaced cv axels, radiator, and trans cooler lines. Truck has been running perfectly fine and the night of New Years it died on me. While driving my engine died I pulled over and kept turning...

www.tahoeyukonforum.com

 

[WestCoastie]

See the post below for specific fuel pressure test and specs. Replace the fuel pump relay just to rule it out; maybe test with the old one and again with a new one.

The Flex Fuel system on your year will have an inline fuel filter on the driver's side frame rail (near the alcohol sensor); consider replacing it if the age is unknown.

Fuel delivery?

Hello all I have a 2003 Yukon Denali 6.0 with 170k miles. Purchased about 6 months ago I’ve currently replaced cv axels, radiator, and trans cooler lines. Truck has been running perfectly fine and the night of New Years it died on me. While driving my engine died I pulled over and kept turning...

www.tahoeyukonforum.com

New fuel filter with maybe 1k on it.

Relay is brand new and good. Fuse is good.

I forgot to mention that I have an occasional issue with the fuel gauge, where it reads empty when I know it has fuel in it. This issue is very intermittent so I mostly forget about it.

I went ahead and ordered the fuel pump. Now I hope it warms up enough for me to want to do it.

 

[mattbta]

Did you replace the Cam Position Sensor during the rebuild and/or recently?

 

[Fless]

Did you replace the Cam Position Sensor during the rebuild and/or recently?

And/or the crank sensor? Either one would be preferably OE, not aftermarket. And if either one was changed, a correlation procedure is highly recommended.

Also is the hard start on a cold engine, or hot, or both?

You may need a new fuel pump lock ring, too, depending on the condition of the existing one.

 

[WestCoastie]

Did you replace the Cam Position Sensor during the rebuild and/or recently?

Yes, I replaced cam and crank sensors. Mostly because they fell apart getting them off. Scanner shows them working though. That thought definitely ran through my head though.

 

[WestCoastie]

And/or the crank sensor? Either one would be preferably OE, not aftermarket. And if either one was changed, a correlation procedure is highly recommended.

Also is the hard start on a cold engine, or hot, or both?

You may need a new fuel pump lock ring, too, depending on the condition of the existing one.

The hard start happened whenever it felt like it, hot or cold didn’t make a difference. The hard start happened more often than not.

Might need a new lock ring. I’m holding out hope I don’t. It was a Texas plains truck and now in the NW where it gets washed regularly. There is almost no rust on it.

 

[WestCoastie]

Would fuel pressure regulator on the rail be a culprit? I have not changed it out nor do I know how to test it.

 

[RST Dana]

If you apply voltage to the pump and it works, then maybe the issue is voltage source coming to the pump. Any testing done on the voltage source?

 

[mattbta]

Yes, I replaced cam and crank sensors. Mostly because they fell apart getting them off. Scanner shows them working though. That thought definitely ran through my head though.

Did you use OEM? If not, does it do this:

That's mine with a non OEM cam sensor in it. Swapped to OEM and it starts first try, every try. I did a cam/crank correlation as Fless suggests, but these engines just don't like non OEM cam sensors. (I did the relearn again after putting in the OEM).

 

[WestCoastie]

I mean that does sound like it. But I feel like all hard starts kind of sound like that?

I spent the extra money after reading on here and when I did the rebuild I got OEM sensors.

The thing that’s got me leaning toward fuel pump, is its obviously been a problem in the past. The random fuel gauge issue. And the fact that it won’t keep pressure up at the rail after everything is turned off.

 

[WestCoastie]

If you apply voltage to the pump and it works, then maybe the issue is voltage source coming to the pump. Any testing done on the voltage source?

Like the battery or ECU