Stumble/Hesitation AND stalling: *solved, fuel pump*

[Bill 1960]

No good answer from dissection of the pump. It is a somewhat complicated unit, all the fuel flow is not just one way. There’s a little venturi nozzle at the base as well as some sort of valve at the top of the filter canister that looks like a regulator or bypass. Plus the path through the filter and out to the engine. So 3 ways fuel could exit the pump.

Perhaps some of the plumbing is to eject entrained air and it was failing? There was plenty of good old Texas dirt in the filter and some residual crud in the bucket that surrounds the pump.

 

[Doubeleive]

No good answer from dissection of the pump. It is a somewhat complicated unit, all the fuel flow is not just one way. There’s a little venturi nozzle at the base as well as some sort of valve at the top of the filter canister that looks like a regulator or bypass. Plus the path through the filter and out to the engine. So 3 ways fuel could exit the pump.

Perhaps some of the plumbing is to eject entrained air and it was failing? There was plenty of good old Texas dirt in the filter and some residual crud in the bucket that surrounds the pump.

hook that fuel pressure gauge back up and see what it shows now, my bet is it's a hair higher at idle, mine sits right at 44 most of the time

 

[Bill 1960]

hook that fuel pressure gauge back up and see what it shows now, my bet is it's a hair higher at idle, mine sits right at 44 most of the time

That’s a good idea. But is this Harbor Freight gauge accurate enough to tell the difference LOL.

If I do I’ll read the live data with my scan tool also and see how it compares to what the ECM sees.

 

[Doubeleive]

That’s a good idea. But is this Harbor Freight gauge accurate enough to tell the difference LOL.

If I do I’ll read the live data with my scan tool also and see how it compares to what the ECM sees.

more of a curiosity thing, if it shows a smidge better maybe that's all it was, like you said when it got hot, unrelated but I had a smart phone that died a fairly slow death I figured it was the cpu taking a c-rap, when I bought a new one I had the option to connect them together with a cable to transfer all the data over but the old phone had got so bad it wouldn't even boot anymore so I stuck it in the freezer with the cable hanging out, let it sit a few minutes and then reached in and turned it on, sure enough it booted and ran just long enough to transfer the data over to the new phone. heat kills

 

[torch]

I would replace the FPCM just because it is a 2008. They had a lot of trouble with water and junk getting inside the module. I think there was a recall where the dealer would put sealer around the seams of the FPCM. Also at some point GM added a rubber shield/flap in front of the FPCM to protect it from road debris. I have a 2009 Tahoe and it would stall when making right hand turns and set a P069E. It a lot of water had gotten inside the module and the sloshing water during the turn and killing the power to the pump. I just ordered a new pre-programmed FPCM and all is good now. If you don't have the rubber shield in front of the FPCM I would suggest you make one for your off roading.

 

[Bill 1960]

After 5 days driving on the new fuel pump I’ll call it and say that was the cause of both issues. Hasn’t misfired once since the pump. And I’ve done a lot of 4x4 and 4L operation with no stalling.

The part was a Delphi FG1054. Took the shop 2 hours to swap it in.

I also bought the Dorman FPCM / FSCM part number 601-022. Which is plug and play no dealer flash required. I haven’t installed that because I wanted to evaluate the results of the pump change. Later this week I’ll install it and run it for a week or so to verify it, then I’ll have a known good spare. I’ll also be fabricating a skid plate to shield it.

Plugs and wires are on hand. I’ll install them at my convenience since it’s back to running fine.

Thanks to everyone who helped work through these problems!

 

[Geotrash]

After 5 days driving on the new fuel pump I’ll call it and say that was the cause of both issues. Hasn’t misfired once since the pump. And I’ve done a lot of 4x4 and 4L operation with no stalling.

The part was a Delphi FG1054. Took the shop 2 hours to swap it in.

I also bought the Dorman FPCM / FSCM part number 601-022. Which is plug and play no dealer flash required. I haven’t installed that because I wanted to evaluate the results of the pump change. Later this week I’ll install it and run it for a week or so to verify it, then I’ll have a known good spare. I’ll also be fabricating a skid plate to shield it.

Plugs and wires are on hand. I’ll install them at my convenience since it’s back to running fine.

Thanks to everyone who helped work through these problems!

Awesome!!! So glad you got it sorted out!

 

[Joseph Garcia]

Thank you for closing the loop and confirming the source of your issue. Much appreciated.

 

[jeremiahm]

I replaced my fuel pump this weekend as well. Had the rough idle at stops, also a spike in RPM when coming to a stop (shift to 1st?) and had experienced some stalls and crank/no starts the last two weeks, including a tow. 3 days of driving and idle smooth and the spike in RPM is virtually gone, no stalls either. My MPG seems to be +1 as well. Pump was making some noise that was hard to notice until I could get close to it (I cut a hole in the floor). New pump is almost silent. Used same Delphi pump as @Geotrash. Truck has 150k on it.

 

[OR VietVet]

I still cannot wrap my head around cutting a hole in the floor. Just sayin'.