on a 95 4.3 C.P.I. the regulator has a torx adjustment screw on the side, can it be turned to achive the 58-61 psi thats required? and do you turn it clockwise or counter clockwise?

 

What is your fuel pressure at now? I don't think there is any adjustment in the regulator.

 

Some regulators are adjustable, some are not. If yours has a torx screw on the back end, it is adjustable. Turning the screw clockwise will increase fuel pressure, counterclockwise decreases it. 1995 CMFI spec is 55psi to 61psi. Anywhere in that range is fine, and the PCM will be able to maintain the proper fuel mixture by adjusting injector pulse width. If pressure is not within spec, either too high or too low, the PCM will not be able to maintain the proper fuel mixture and you will experience driveabilty issues or a no start condition. On CMFI systems, you can adjust it very easily by removing the plenum and activating the pump. On CSFI systems it's a little more involved, but it can be done.

 

@ Captain Hook -

Love the caption in Your post !

shovel ready indeed

 

hi, i have central port injection (C.P.I) on my 95 with an adjustable regulator that is mounted on the passenger side of the injector. when i am checking my fuel pressure should i be checking it while the motor is at idle? & should the gauge read btwn 55 and 61 while idling? after replacing the fuel pump the psi was at 54 psi with a near empty tank. then i filled up the tank all the way and the psi now reads 55 psi. can i get 2-3 psi by turning the torx screw clockwise?

 

Don't adjust the regulator until we know if the fuel delivery system is good.

Key ON, engine OFF, fuel pump running: pressure must be 55psi to 61psi and must remain above 50psi for at least 10 minutes after the pump shuts off. If it fails either part of the test, it means there's a problem. It does not determine what the problem is, only that one exists. Further diagnosis is necessary to determine what's causing the problem. GM does not publish any "engine running" fuel pressure specs for this engine. Post your results.

 

today my fuel pressure was at 54 psi at idle... so i will do this test today and if it does not fail i can raise the pressre? and how much do i turn the screw? and what size is the bit? and where do i buy it? i will post results to...

 

GM does not publish any "engine running" fuel pressure specs for this engine. They can not be used for diagnostic purposes. There are far too many variables involved such as elevation ASL, engine load, engine condition, etc etc.

With the key ON, engine OFF, and fuel pump running, if pressure is 55psi to 61psi, it will do no good to adjust it. If it is not within specs, it will need some diagnostics to figure out what the problem is. You can't immediately assume the regulator is set to low, or if it's the regulator at all.

 

ok i did the test twice, once yesterday and the other the day before. the results were different between the two tests however so i will post both results....

heres the recent test

62 psi during prime
59 psi right after prime stopped
58 psi after 30 secconds of prime stop
56 psi after 1 minute
55 psi after 3-4 minutes
55 psi after 5-6 minsutes
54 psi after 10 minutes
54 psi after 15 minutes
54 psi after 30 minutes

and these results from the first test

62 psi during prime
59 psi right after prime stops
58 psi 1 min after prime stopped
54 psi after 5-6 mins
52 psi after 10 mins
52 psi after 15 mins
50 psi after 30 mins

so can i raise the running pressure?

 

Pressure and leakdown are both darn near perfect. Spec is 55psi to 61psi and not less than 50psi after 10 minutes. Write off your reading of 62psi to gauge error, and you're at the upper end of the spec. The fuel pump and fuel pressure regulator are working as they should. You can raise the pressure only if you want problems... and you'll get them

Edit: Also see post #8