Fuel Pressure Test

[MackAttack]

Ok just ran the test. Turned the key to the “on” position, and the PSI jumped to 50. Turned the engine over, and it jumped to 58-60 PSI even the first 2 starts where the engine kept dying. The second I killed the engine, the psi instantly dropped 8-10 PSI (50 ish). Turned it off, left it for 30 mins, and it maintained 50 PSI. When I first put the attachment, gas shot out, so I was confused because that means that it has pressure? Anyway, Started it again, and went right back to 60. (PS: yesterday I noticed on a little harder accelerations such as speeding up to merge and such, I feel like the engine is being starved of gas because I can hear it bogging and it looses power. This does not happen all the time though.) Back to what I was saying, when I was letting it idle for the second time it was staying at 60, but all of a sudden dropped to 43ish PSI. Is this normal? Engine idled fine even after sudden drop
Mack

 

[Fless]

I suggest that you'll get better feedback if you keep your posts to one thread about this issue (since you have another one going already). Spreading the posts over multiple threads causes confusion and duplicate answers.

 

[MackAttack]

I suggest that you'll get better feedback if you keep your posts to one thread about this issue (since you have another one going already). Spreading the posts over multiple threads causes confusion and duplicate answers.

Ah ok. Some of the forums I’ve been in have a maximum number of replies, not really sure how it worked here

 

[Doubeleive]

Ah ok. Some of the forums I’ve been in have a maximum number of replies, not really sure how it worked here

normal running psi is low 40's, I believe 42-45 is normal.
so 60 running is high
key on, engine off it should be 50-65 (pre-start), then after start it should drop down to 43 or so and stay around there
unless yours is a hybrid, then the specs are different.
i would keep testing, you may have a intermittent problem
check all your grounds and you can check the fuel pressure control module harness also sometimes there is water intrusion or rust/corrosion because it is up under the rear by or under the spare tire.

***also from your description it kind of sounds like it might not be fuel pressure related, if the engine is not kicking over the computer may be trying to compensate with more fuel at startup, just a hunch i could be wrong.

 

[MackAttack]

normal running psi is low 40's, I believe 42-45 is normal.
so 60 running is high
key on, engine off it should be 50-65 (pre-start), then after start it should drop down to 43 or so and stay around there
unless yours is a hybrid, then the specs are different.
i would keep testing, you may have a intermittent problem
check all your grounds and you can check the fuel pressure control module harness also sometimes there is water intrusion or rust/corrosion because it is up under the rear by or under the spare tire.

***also from your description it kind of sounds like it might not be fuel pressure related, if the engine is not kicking over the computer may be trying to compensate with more fuel at startup, just a hunch i could be wrong.

Ok awesome let me check my grounds and electricals ans get right back to you guys. It stays at about 50-60 psi for a little while then will drop to the low 40’s. I was thinking if I might be a spark plug? I noticed when I killed the engine, I heard a faint “hissing” sound from the engine bay. Could this be the pressure releasing? Let me get back to you guys after I check my grounds and if there are corrosions on the electrical.
Thank you,
Mack

 

[Doubeleive]

Ok awesome let me check my grounds and electricals ans get right back to you guys. It stays at about 50-60 psi for a little while then will drop to the low 40’s. I was thinking if I might be a spark plug? I noticed when I killed the engine, I heard a faint “hissing” sound from the engine bay. Could this be the pressure releasing? Let me get back to you guys after I check my grounds and if there are corrosions on the electrical.
Thank you,
Mack

some vacuum type noises when shutting off a engine are normal, unless it's something that seems way out of the ordinary
did you do any work to it recently? any other symptoms? check engine light?, you could scan it anyway just to see if there are any historical codes saved.

 

[Foggy]

Don't know the year/info on your truck... But 58 psi is the normal. Your FPCM regulates your fuel pressure
Maybe it's the issue... If you only have low 40's you certainly have a problem

 

[Doubeleive]

Don't know the year/info on your truck... But 58 psi is the normal. Your FPCM regulates your fuel pressure
Maybe it's the issue... If you only have low 40's you certainly have a problem

Presuming it is posted correctly as a gmt900 and it is not a hybrid then engine running psi should be 43-45 psi
mine runs at 43psi all day long i have monitored it many times

 

[MackAttack]

some vacuum type noises when shutting off a engine are normal, unless it's something that seems way out of the ordinary
did you do any work to it recently? any other symptoms? check engine light?, you could scan it anyway just to see if there are any historical codes saved.

I did do work on it, I replaced the entire cooling system. I was suspecting something else also, when me and my friend were checking the pistons of the engine by removing the spark plugs to see if it was burning oil, one broke. We then dug around in his truck until we found and old crap spark plug and threw it in just so the truck would run again. I was thinking maybe it could be leaking pressure from there or if that’s a totally unrelated issue. I bought NGK laser Iridium Premium spark plugs yesterday and I’m throwing them in today. I am also going to scan it again for past codes. Yesterday while driving, my coolant temp went to zero and said the engine was hot. After driving for about 5 more mins (this is a bad wiring harness for the coolant temp sensor by the way) a check engine light came on. When I got to my college, I popped the hood, disconnected the battery, and everything went back to normal. Could the check engine light maybe be caused by something else too? Either way I’m scanning it right now

Thank you so much for your help
Mack

 

[MackAttack]

Don't know the year/info on your truck... But 58 psi is the normal. Your FPCM regulates your fuel pressure
Maybe it's the issue... If you only have low 40's you certainly have a problem

I have been seeing all sorts of different numbers all over the internet so that’s why I was kinda confused. Sorry I forgot to mention, the truck is a 2009 Chevrolet Suburban 1500 LT, 5.3L V8 Naturally Aspirated with Flex Fuel and is not hybrid. Although I wish I bought the hybrid one in 09