fuel pressure?

[grnadnasty84]

i have an 84 gn with: 87 ecm and coil pack, cold air intake, exhaust, and minor other stuff. when i bought the car it had a hot wire kit and high flow fuel pump, but the previous owner just bundled up wires trying to slow the pump down and i think the pressure was set at about 25 to 30 lbs. i took all that off and went back to stock pump and set the pressure at 40 lbs, what i think is stock. it has been running fine but i think its a little rich, it's real sluggish in the mornings. where do these cars like to sit in respect to fuel pressure? also if i drop it to 30 lbs and keep of the turbo as much as possible will i get better gas mileage? thanks.

 

[cool 84]

Why would you put the stock pump back in? These cars need a high flow pump. For a stock hotair, start with 38-40psi with the vacuum line off for setting. Make sure you do the adjustments with the line off.

If you lower the pressure your 02 will compensate and add more fuel anyway at cruise and you risk leaning it out at WOT.

 

[Jerryl]

i have an 84 gn with: 87 ecm and coil pack, cold air intake, exhaust, and minor other stuff. when i bought the car it had a hot wire kit and high flow fuel pump, but the previous owner just bundled up wires trying to slow the pump down and i think the pressure was set at about 25 to 30 lbs. i took all that off and went back to stock pump and set the pressure at 40 lbs, what i think is stock. it has been running fine but i think its a little rich, it's real sluggish in the mornings. where do these cars like to sit in respect to fuel pressure? also if i drop it to 30 lbs and keep of the turbo as much as possible will i get better gas mileage? thanks.

Fuel pressure depends largely on the chip writer. Stock is around 37, line off.
Not sure why anyone would want to slow the pump down, unless you have too big of an injector and an incorrect chip installed. All specualtions untill you set your baseline.

FP and gas mileage are not necessarily related as the ECM will largely control the mixture based on O2 feedback in closed loop operation. However, FP, boost, octane, and KR are related based on the chip program.

Your main concern with these cars is not really mileage, but knock. Gas mileage is only an indication of a good running and correctly tuned car, plus driving style/habits. You may want to invest in a scan-tool if you plan on doing the work yourself. Then, start with the basics so you have an accurate baseline and know what you have.
As Cool 84 stated, get the other pump back in, or start saving for head gaskets and/or new motor.

 

[grnadnasty84]

i put the stock pump back in to get rid of the mess the last owner made by putting in the high flow, you should have seen it. i'll go to high flow when this one cuts out or i get another car and can stop using this one as my daily driver. anyways, thanks for the input, i guess i'll just keep it where it is for now.

 

[Jerryl]

i put the stock pump back in to get rid of the mess the last owner made by putting in the high flow, you should have seen it. i'll go to high flow when this one cuts out or i get another car and can stop using this one as my daily driver.........

What mileage are you getting and where are you located?

 

[grnadnasty84]

what gas mileage? as much as i can. located in dallas, texas.

 

[grnadnasty84]

at its best i think it was around 20 mpg highway, now its about 15-17 mpg.

 

[grnadnasty84]

also, kinda off this topic, what fuel filter is everyone using?

 

[cool 84]

i put the stock pump back in to get rid of the mess the last owner made by putting in the high flow, you should have seen it. i'll go to high flow when this one cuts out or i get another car and can stop using this one as my daily driver. anyways, thanks for the input, i guess i'll just keep it where it is for now.

When it cuts out you blow headgaskets. Was this wiring mess inside of the tank? Any other mods, specifically, stock chip?

 

[cool 84]

also, kinda off this topic, what fuel filter is everyone using?

Any stock replacement from any autoparts store. As far as I know one any stock replacement is as good as the other.