No start, low fuel pressure after cam swap.

[stilts]

Hi All,

I just did a cam swap on my 2018 CTS-V with the LT4 but can't get it to start and need a sanity check.

Cam is the BTR Gen V stage 1 supercharger with 38% fuel lobe and VVT is locked out. I determined the hpfp lashcap required was .060, which is installed. It would be interesting if that others found the same .060 lash cap needed.

When I attempt to start, engine cranks over, low side fuel pressure stays above 60psi, high side will climb to 400-500psi but has soon as the injectors open the pressure drops to below ~35 and only recovers 10-20psi. After a few more attempts I eventually get a P00C6 (Fuel rail pressure low during cranking). I took the supercharger off and confirmed the hpfp is plugged in, then I removed the hpfp to visually inspect the lash cap and follower. I checked the grounds on both sides of the block and the grounds on the back of the cylinder heads. And to be thorough I confirmed engine has spark and pumps 185psi on a compression check.

So far I'm thinking everything points at the hpfp. If the hpfp is bad it must have gone bad during the cam swap, but not sure that happened.

So my questions are:

Is there anything else I can check to confirm the hpfp is bad, can it be taken apart?
Could this be tune related? It is my understanding that even with the stock tune it will start just run the crap, right?


I attached the log and the tune that is in the car now. I even tried the stock tune with the same results.


Any help would be greatly appreciated!



BTRPD1BaseMAF-Only.hpt
FirstTryMAF-Only.hpl

[96GS007]

If you didn't check pre-load with the lash cap, you may have bottomed out the HPFP and trashed it.

[RaceReadyTuning]

38% Fuel lobe needing .060" cap on a LT4 pump is pretty unusual.
I'd be willing to bet the lt4 hpfp doesnt need the lash cap or if any is needed it is very small.

[tfrost92]

Same cam with an LT4 hpfp, I did not use a lash cap. .060 would have for sure bottomed out the pump. Although I did have minimal preload BTR stated as long as I had a measurable amount it would be fine.

[edcmat-l1]

I agree sounds like you broke the HP pump.