fuel pressure question=95 jimmy

[ousooners1baby]

at start i have about 52 psi then when accelerated it stays about the same or even drops a little. book says it should go to 64 psi pretty quickly.ive recently changed the cpi unit or spider.before change there was obvious leak on pass side of intake. i did not change the nut kit or whatever it is(not even sure what it is).my fuel pump is quite loud and even gets quieter and louder with the change in rpm of the motor. this may be normal i don't know. do i still have a leak or is my fuel pump or filter bad. please help!!!

[BlazerLT]

Originally Posted by ousooners1baby

at start i have about 52 psi then when accelerated it stays about the same or even drops a little. book says it should go to 64 psi pretty quickly.ive recently changed the cpi unit or spider.before change there was obvious leak on pass side of intake. i did not change the nut kit or whatever it is(not even sure what it is).my fuel pump is quite loud and even gets quieter and louder with the change in rpm of the motor. this may be normal i don't know. do i still have a leak or is my fuel pump or filter bad. please help!!!

You measure fuel pressure with the key on and engine off.

You might want to replace your fuel filter ASAP because I think your fuel pump is trying hard to push fuel through a plugged filter.

[94 Jimmy]

Check out: http://www.asashop.org/autoinc/feb2000/techtotech.htm
It's and ASA Tech to Tech page discussing the CPI and required fuel pressure.
They say:
"We say the system running pressure should be slightly lower than KOEO (normally between 59 to 61 psi), but never go below 57 psi. There is a 30 percent fuel delivery loss at 56 psi, which can cause hard starting and driveability problems."
Hope this helps, try the fuel filter first, since it's easiest. Then move on to the pump.
Check out Rockautol.com for good variety, and parts prices.
See ya
94

[ousooners1baby]

i looked in the plenum and see no signs of leak.pulled the vacuum hose off the regulator no gas just good vacuum. is there any way bad plugs or wires could make the pressure not build up if they weren't hot enuff? man im tired of this .what do i do?pressure with key on was 59psi. when the pump quits it drops about a digit every 15 or so seconds. hope that helps.

[BlazerLT]

Vacuum hose off of the regulator?

What?

[BlazerLT]

Vacuum hose off of the regulator?

What?

[ousooners1baby]

ok, i guess youre saying theres no hose on a regulator? i kinda wondered if he was right.i was told gas would come out of the back of the intake if the reg. was bad. i guess thats just a vacuum line?what else should i check?

[ousooners1baby]

Do you see a change in engine performance or in the pump noise when the vacuum hose is removed from the pressure regulator? Is mileage bad?

If mileage is acceptable, and a noticable change in performance is noted when regulator vacuum source is removed, the fuel system is functioning as it should, even with the pressure reading as it is. The pressure regulator will reduce the pressure of the incoming fuel to a level calibrated for the engine.

If fuel blows out of the vacuum line port on the regulator, the regulator needs to be replaced


that was told to me today














that was told to me on another site.

[BlazerLT]

95 jimmy I believe has the CPI vortec 4.3L in it right?

Or is yours the TBI?

[ousooners1baby]

Originally Posted by BlazerLT

95 jimmy I believe has the CPI vortec 4.3L in it right?

Or is yours the TBI?

cpi cpi cpi

[BlazerLT]

There is no vacuum line on the fuel pressure regulator.

[ousooners1baby]

ok.so what was the vacuum line on the rear of the manifold?could the nut kit be leaking? i see you talk alot about a maf sensor. where is this jewel?i still think my cpi unit or reg. or nut kit is leaking. i just don't see how.do i need to be canadian to figure it out?

[BlazerLT]

The big vacuum line goes to the brake booster.

The small vacuum line goes to the Vacuum ball for the heater controls.

[ousooners1baby]

could the nut kit be leaking? i see you talk alot about a maf sensor. where is this jewel?i still think my cpi unit or reg. or nut kit is leaking. i just don't see how.

[BlazerLT]

Measure fuel pressure with the key on and the engine off.