2004 6.0 NV4500 Tahoe

[Dantheman1540]

So is my fuel pump dying? Can’t remember what oem specs are but I thought 50primed and 40psi bleed down and hold was normal

 

[Fless]

Shoot. Seems like it should be a bit higher and not bleed down so quickly when not running. Leaky injector? Bad fuel pump or FPR?

KOEO specs for NBS V8 engines:
Non-Flex: 55 to 62 psi
Flex: 48 to 54 psi

 

[Fless]

What kind of pressure when it's running at various RPMs?

 

[Rocket Man]

So is my fuel pump dying? Can’t remember what oem specs are but I thought 50primed and 40psi bleed down and hold was normal

Leave it on for awhile. If it’s the FPR or a small leak it will show over time.

 

[George B]

Did you bleed the air out of the tester hose?

 

[Dantheman1540]

Did you bleed the air out of the tester hose?

Damn I’m an idiot, no I didn’t I was super rushed.

Leave it on for awhile. If it’s the FPR or a small leak it will show over time.

I will have to do further testing Friday when I have more time and I will leave it for longer to see.

What kind of pressure when it's running at various RPMs?

I didn’t get time to check I was in a rush but I’ll check that Friday

Shoot. Seems like it should be a bit higher and not bleed down so quickly when not running. Leaky injector? Bad fuel pump or FPR?

KOEO specs for NBS V8 engines:
Non-Flex: 55 to 62 psi
Flex: 48 to 54 psi

Huh didn’t know it was that high but makes sense most people set their adjustable FPRs to 58. Ill inspect better for a leaky injector tomorrow when I leave for work.

 

[randeez]

Should've kept the taco.

Also
58psi=400kpa
43psi=300kpa
That's where the oddly specific psi comes from

 

[Dantheman1540]

Should've kept the taco.

Also
58psi=400kpa
43psi=300kpa
That's where the oddly specific psi comes from

I’ll probably swap all my **** into the taco tomorrow or Friday, it takes me a good 15minutes to swap all my **** and I always end up forgetting stuff if I swap at 1030pm after class in the dark or 6am before work in the dark.

Ahhhh that explains the oddly specific psi, guess I’ll order a bucket assembly off Amazon just in case further testing proves it to be the pump. If not I’ll return it lol

 

[Dantheman1540]

Alright more testing was done this morning, the first prime pumped to 52 and bleed down to 40 again, tried to start and no start after 10 seconds, cycled the key again and got 52 which bled down to 40 but immediately started like it usually does. Idle pressure was between 50-55 same with WOT neutral revving, I have not driven with the gauge hooked up yet although I have no reason to think it would be any different because it drives and shows perfect AFR during all driving conditions.

Yes, I did bleed the pressure out of the gauge hose this time, yayy I smell like fuel now.

At this point, although the pressures arent up to 62 I personally don't believe it's a fuel pump problem since the pressures are consistent and when it won't start on that first crank it has the exact same pressure as it does when it does start on the second crank. If there was a noticeable difference between the initial crank FP and the second crank FP I would say its likely a fuel pump/bucket/FPR issue.

Since the issue shortly before this was related to a cam position sensor is it possible I need to do a crank relearn or anything? I'm fairly certain it can be done with HPT special commands and functions. Or is it possible I have an INOP cam position sensor? I cleaned the area fairly well before I installed it but I installed it blindly giving it the reach around.

 

[George B]

Do you have a tech2? Do a case relearn.