fuel pressure question=95 jimmy


ousooners1baby
04-27-2005, 08:47 PM
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
04-27-2005, 10:52 PM
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
04-27-2005, 11:00 PM
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
04-28-2005, 05:03 PM
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
04-28-2005, 05:08 PM
Vacuum hose off of the regulator?

What?

BlazerLT
04-28-2005, 05:09 PM
Vacuum hose off of the regulator?

What?

ousooners1baby
04-28-2005, 08:08 PM
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
04-28-2005, 08:19 PM
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
04-28-2005, 09:35 PM
95 jimmy I believe has the CPI vortec 4.3L in it right?

Or is yours the TBI?

ousooners1baby
04-28-2005, 09:59 PM
95 jimmy I believe has the CPI vortec 4.3L in it right?

Or is yours the TBI? cpi cpi cpi

BlazerLT
04-28-2005, 10:05 PM
There is no vacuum line on the fuel pressure regulator.

ousooners1baby
04-29-2005, 03:57 PM
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
04-29-2005, 10:21 PM
The big vacuum line goes to the brake booster.

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

ousooners1baby
04-29-2005, 11:33 PM
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
04-29-2005, 11:42 PM
Measure fuel pressure with the key on and the engine off.

ousooners1baby
04-29-2005, 11:53 PM
Measure fuel pressure with the key on and the engine off.
ok i did that.still bleeds off slowly, very slowly.why?

BlazerLT
04-29-2005, 11:54 PM
That is normal for the pressure to bleed off slowly like that.

What is the pressure? You only stated the fuel pressure with the engine running.

ousooners1baby
04-29-2005, 11:58 PM
56psi.
maf sensor where?

BlazerLT
04-30-2005, 04:44 PM
56psi.
maf sensor where?

You don't have a MAF sensor.

Are you having any driveability problems, check engine lights?

Have you done a tuneup lately?

ousooners1baby
04-30-2005, 06:19 PM
ok,no ses lights,drives pretty intermittent.you can tell its not getting proper gas or fire.changing plugs,wires,and filter 2nite.anything else control how the gas works.tps or other sensor.thanksl LT.

BlazerLT
04-30-2005, 07:48 PM
Remove the rounf IMTV valve and take a look down into the upper plenum and check for washing from leaking fuel.

Change the cap and rotor when you do a tuneup.

ousooners1baby
05-01-2005, 10:44 PM
Remove the rounf IMTV valve and take a look down into the upper plenum and check for washing from leaking fuel.

Change the cap and rotor when you do a tuneup.

dunnit, and runnin like brand new.thanks lt!fuel filter was stopped up.

Add your comment to this topic!