What's fuel pressure supposed to be?

[89Vette]

Searched on the terms fuel and pressure. Looked through tons of threads. Spent close to an hour and never found what I'm supposed to see when measuring FP.

Mine is 34PSI (42 w vac unplugged).

I figure this is probably "within acceptable operating parameters". :bwgy:

Please confirm!

gp

[Y33TREKker]

The downloadable manual suggests that "Key On" fuel pressure should be between 333-376 kpa (48-55 psi).

[89Vette]

There's a downloadable fsm somewhere? Didn't think user manuals showed fuel pressure.

I'd have to think 48-55PSI is the unregulated fuel pump pressure. If correct, mine may be low. Still might be high enough for the ODB2 computer to compensate though.

[Y33TREKker]

Those pressures were actually taken from a downloadable Isuzu Workshop/Repair Manual, not a users/owners manual.

2000 Isuzu Workshop Manual (http://www.vehicross.info/modules.php?name=Downloads&file=viewarticle&id=40)

And from this thread; http://www.vehicross.info/forums/showthread.php?t=20985


My initial search term was "fuel pressure", and when following one of the "fuel pressure regulator" search results, I saw a link that said "fuel system diagnosis". After that I used "fuel system diagnosis" as my search term, and the fuel pressure readings were listed under a few different topics.

Most of the results were in section 6E - Engine\ 6VE1 3.5L Engine Driveability and Emissions.

[Ebenezr]

my pressure was 38 key on and 33 engine on. It did not change after a new fuel pressure regulator and fuel pump. Fuel pressure of 48 to 55 is the pressure before the regulator not the pressure on the rail...I believe.

[89Vette]

Apparently, we have adjustable FPR's. Which means we can change pressure. So, I could raise it above the 34PSI observed with key on.

Has anyone effected a change in MPG by changing FP? Did you raise it to accomplish that?

More pressure = shorter PW and better atomization.

Theoretically.