Dealer not honoring warranty work..2018 5.3 Yukon issues

[Kpwweb]

The key to testing fuel pumps is LOAD. Go up (or accelerate up) a very long hill. Accelerate hard from a rolling start, etc... The engine needs to demand a large quantity of fuel at once (or a large amount over a long period of time). The other key for the fuel pumps is heat. Apparently there is a batch, or batches that fail under heat and load. Mine stumbled horribly with both those conditions. Would run fine normally--normal acceleration, etc. I did have a stumble every so often at idle, but would state the truck ran fine otherwise.

But when I floored the throttle one day--wham! The engine bucked violently AND THEN took off. I repeated the test and it did the same thing. Still accelerated normally under "normal" acceleration. So the best way to test it I found is in a safe place, roll at 5 mph and then floor the accelerator and hang on--see what it does.

 

[Bob2C]

Accelerated fine under conditions you stated above. No issues at all. So that rules out fuel I assume


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[swathdiver]

I did the fuel pressure test. Got it up to 50 from a dead stop. It didn’t drop. The low reading around 31 was idling in drive stopped. It fluctuated to 45. Do you think this is a fuel delivery problem?

Bob, I don't know how your fuel system works, meaning what pressures are normal depending on situation. Does someone here have the shop manual for a K2 and the DI motors?

 

[Tiredmechanic23]

Wonder if it could be in the high pressure system. A scanner that can read it would be needed. High pressure readings can be several thousand PSI.

I have seen a C7 stumble in certain conditions and they chased their tail on it replacing the in tank pump and the high pressure pump for it to end up being a check valve or something restricting flow.

 

[Bob2C]

Did some logging of high pressure. Also noticed low side dipped to 15psi while at idle in drive.




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[swathdiver]

Did some logging of high pressure. Also noticed low side dipped to 15psi while at idle in drive.




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Yeah, that's what I'd be looking for. So do these have a pump in the tank and another to increase pressure at the fuel rail? Kind of like a lift pump and an injector pump?

 

[Bob2C]

Yeah, that's what I'd be looking for. So do these have a pump in the tank and another to increase pressure at the fuel rail? Kind of like a lift pump and an injector pump?

Yes I believe they have both. My Kia gdi does.


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[Tiredmechanic23]

Yeah, that's what I'd be looking for. So do these have a pump in the tank and another to increase pressure at the fuel rail? Kind of like a lift pump and an injector pump?

Yup. High pressure pump is under the intake on the valley cover.

 

[smokey_mountain]

Bob and all please keep this research up, I am following this thread and I did not move away. I just have to do a ton of paperwork prep for tomorrow arbitration. As GM told me, "go ahead try arbitrage we will drown you in paperwork" they were not kidding...

 

[HiHoeSilver]

Bob and all please keep this research up, I am following this thread and I did not move away. I just have to do a ton of paperwork prep for tomorrow arbitration. As GM told me, "go ahead try arbitrage we will drown you in paperwork" they were not kidding...

They told you that? Smh. Let us know what happens!