2015 Silverado 6.2 Dropping High Side Fuel Pressure

[jc052685]

LT4 HPFP & Injectors.
2.9 whipple at about 10psi.
Mild blower cam
93 pump gas only.
Bosch 044 Secondary lift pump on a hobbs switch

Truck will sometimes drive will no issue. Though lately it drops high side pressure like crazy. Under 200psi. Truck was fine on the dyno on Wednesday. Drove it yesterday and the high side drops. We fought it for most of the day and then I threw it on the dyno and it was fine. Took it off the dyno and it was still fine. Had it on the dyno Wednesday and it was still fine. Now yesterday it started doing it again.

Street 5 you will see it is fine. Street 6 not so much (2min 45sec).

[jc052685]

No one huh?

[Ben Charles]

I'll look later

Does the cam have the fuel lobe?

[Ben Charles]

Honestly on pump gas you shouldn't have issues... especially with the lt4 hardware, unless the lt4 hpfp is having a problem

[jc052685]

Has a lobe yes. Making right at 720whp on straight 93. I was told to suspect the bleed valve but the fact that is will be fine then wont be has be suspicious of something being off in the tune. Though it looks like I may be pulling the blower to get to the pump.

[Ben Charles]

On 93 with a Lobe, you should not be having fueling issues

I'm intrigued now so I'll look later

[GHuggins]

As long as your not going overly rich or something like that all at once, that setup should handle 750 to 800 to the tires good enough. As long as your not seeing supply drop out and your not laying a ton of fuel to it, it's most likely a bad hpfp.

[jc052685]

AFR is dead steady on the dyno (.89 lambda). Have not had it act up on the dyno yet.

[GHuggins]

It most likely would if you were using road simulations on the dyno where it simulates vehicle weight and air resistance... BUT nothing can compete with real world scenarios...

[jc052685]

Ran it loaded on the dyno. This pull here is like 16 sec long. If that does not fully stress the system I dont know what will.

And currently it acts up just stomping the throttle in the parking lot.... not much load at all compared to this dyno pull

[jc052685]

Your thoughts?

[GHuggins]

Sounds like HPFP... Get a log with the quick stomps while logging low side pressure too... Sounds like it's just the "quick" rail deletes that it's having problems with - drawn out slow revs it stays with fine...

[jc052685]

Well I've got a pump here so looks like I will swap it out this week and report back.

[jc052685]

Ok, new HPFP. No change.

[Ben Charles]

Hmmm just looked at the file pretty quick.... Nothing jumped out at me.. Odd that the Rail pressure dips out around 3400 on the pulls, but not on the dyno. Going to look a little harder later. Something has to be happening.... Rail pressure comes right back when not taxing it too...

[Ben Charles]

EDIT... The MAF table looks pretty lean when in PE mode... after comparing the MAF table to a similar setup it doesn't look like you have enough fuel in it at all.. What is the wideband reading???? I would also target a more rich Lambda reading then .87

[jc052685]

EDIT... The MAF table looks pretty lean when in PE mode... after comparing the MAF table to a similar setup it doesn't look like you have enough fuel in it at all.. What is the wideband reading???? I would also target a more rich Lambda reading then .87

Wideband is on target

[Ben Charles]

Where you reading the Wideband?? Tailpipe? If you look at the pills the 02 Mv are bottomed out in PE..

[jc052685]

What log are you viewing? Look at "street 5". The log where the truck runs fine

[Ben Charles]

I'm viewing 6 where the problem is!! Before rail pressure ever takes a dump there is no fuel in it.. makes sense it would take a dumb in rail pressure if no fuel is being commanded... shows it moving less then 300 g/sec over 2.5lbs (way more then that I'm sure since you still have the factory map)