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carguyjosh, ASE Certified Technician
Category: Chevy
Satisfied Customers: 2172
Experience:  ASE certified , 16 yrs in field
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proper fuel pressure 4 2003 vortec 4.3 v6 x engine

Customer Question

what is proper fuel pressure 4 2003 vortec 4.3 v6 x engine and if mine is at 55 pounds could or will it cause detination pre mature
Submitted: 7 years ago.
Category: Chevy
Expert:  carguyjosh replied 7 years ago.

Proper fuel pressure is 55-62 lbs...


If your fuel pressure is correct, with everything else that you have already tried, I recommend that you go by you local dealer and have the latest drive ability updates programmed into your computer.


It is very common for GM to release an update to address these types of problems. The only way to be sure is to have your computer checked against the GM database to verify what software is in it and if an update is needed...


Thanks, Josh

Customer: replied 7 years ago.
when you r checking fuel pressure and it says 55lbs and you open valve into gas can it goes to 0 does this sound like a weak pump to you and will slightly low pressure do to weak pump cuase predetination sounding like marbles in a rock pollisher commonly refeard to as spark knock
Expert:  carguyjosh replied 7 years ago.

If your pressure is 55lbs when you turn the key on and then drops to 0 when you open the drain valve, this is normal...


The engine control computer only primes the fuel pump for 2 seconds. All that 2 second prime does is charges the fuel rail. The pressure should fall of as soon as you open the system..


If the pump is getting weak, detonation will occur..


You will want to test the fuel pressure with the engine running for a more accurate pressure reading....


Thanks, Josh

Customer: replied 7 years ago.
Josh, I just checked fuel pr. tonight w engine running. 55lbs at idle. If you spike throttle to quarte or half or what ever it only goes to 60 for a split second and falls back to 55 even though you have throttle opend up. While running when I open valve on my test rig to dump off into can the guage goes to 0. I will replace this $250.00 pump myself based on your opinion. Please continue to help as it is important to me not to distroy my crank bearings before I find the culpret.
Expert:  carguyjosh replied 7 years ago.

Your fuel pressure seams to respond properly..I don't want you to replace a pump that is within spec..


If you have a timing light with an advance built in. I would like you to put a paint mark on the crank pulley and connect to #1 plug wire and dial your timing light in to this mark.. Dial your timing light in and once you have a good picture of the mark, I would like you to have an assistant tap the back side of the engine block with a hammer..


What we are looking for is a responce from the engine computer to back off the timing. This will tell us that the computer has control of the ignition timing and that the knock sensor and wiring are functional..


Please let me know....Thanks, Josh

Customer: replied 7 years ago.
I am not that well equiped. I am a carpenter and this is not my cup of tea . I can only make sure my vehicles never get this far out of tune. problem is I recently bought this and I could not here the noise until I took the dog house off to start my tune up and drove to work one day with it off. I have an appointment with ferman chevy monday but was hoping someone would tell me that it sounds like the pump is weak skip the dealer and replace the pump. but it is what it is I have to go to work in the morning I guess I just paid $50.00 to be told to go to the dealer. I dont have a problem with the pro's. My view is solve what I can before I take it to you guy's. what ever your response is I will pay for the coraspondance and info and time thanks dude gotta go. Good night
Expert:  carguyjosh replied 7 years ago.

If you are only hearing this noise with the doghouse off, Honestly...I wouldn't worry about it...

I have worked and tons of these engines and to be very honest with you, they sound awful when the engine cover is off..All of the engine, trans, and driven pulley's noise is funneled right back to the driver...


To be completely honest, I think that if you go into the dealer they will not find anything. If the problem was out of control, the computer would be setting the check engine light and reporting diagnostic codes..


Now obviously, I can't hear the noise myself but if you only hear it with the engine cover off, It sounds like normal engine noise...


Thanks, Josh

Customer: replied 7 years ago.

how do we do this im not happy with the answers

Expert:  carguyjosh replied 7 years ago.

You just don't need to accept my answer.

I am sorry that I could not be more helpful. I don't want to see you spending your money when I fear that you won't get an acceptable outcome....


I can release your question to see if someone else may have another sugestion for you...

Customer: replied 7 years ago.
ok no thanks ...its getting late
Expert:  carguyjosh replied 7 years ago.

No problem. no need to respond back...


Thanks, Josh