What should the fuel pressure be while driving? I was doing some checks on my car last night and I found mine to be around 30psi during normal driving and I noticed that the pressure would drop about 5 psi when I accelerated hard. Does this sound right? My car has been running bad lately, and I wonder if the fuel pump is part of the problem. Thanks.



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Shaun
92 B4C 350TPI
AFPR, Underdrive Pulleys, Hypertech Thermomaster, Dynomax Cat-back, K&N's, Airfoil, Ported Plenumhttp://www.angelfire.com/wi/lhelm99

 

Your fuel pump is dying and is about to go to car parts heaven. :/ Mine acted the same way after I had severely starved it on an auto-x course. Although my base pressure was fine, it would drop while accelerating instead of increase like it should. The engine also was bucking really bad when trying to accelerate at part-throttle, although at WOT it was even stronger than before since it was running a lot less rich.

Normal pressure with the vacuum line hooked up is around 42 psi. I also knew my fuel pump was dying when I'd turn the key to the On position w/out starting the engine and listened to the fuel pump. Instead of a nice strong "whirrr" sound, it was a lower-pitched weak-sounding groan. With a Walbro in-tank pump, (less than $100 for the high-volume model), it's much better.

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Greg Westphal
'87 IROC 305TPI/A4

 

I tend to agree with Greg about the pump being the probable cause.

ODB

 

It could possibly be a bad FP regulator.

 

I know this sounds obvious but have you changed the fuel filter lately?

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Tracy /AKA IROCKZ4me
'86 IROC-Z Camaro
"Cogito ergo zoom"

• 355 cid
• AFR heads
• Arizona Speed & Marine hydraulic roller cam w/ AFR hydra-rev kit
• modified SLP runners
• TRW forged pistons/ceramic coated
• fully balanced
• Edelbrock headers/ceramic coated
• SLP cat-back
• Paxton supercharger
• Nitrous Express nitrous oxide

My IROC-Z
EFI Performance Club on Yahoo
Club IROC-Z

 

Yeah I just changed the fuel filter, that was one of the first things I did to try to help the problem. I guess it looks like it is the fuel pump. Thanks



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Shaun
92 B4C 350TPI
AFPR, Underdrive Pulleys, Hypertech Thermomaster, Dynomax Cat-back, K&N's, Airfoil, Ported Plenumhttp://www.angelfire.com/wi/lhelm99

 

Send my vote in for the pump. But if you wish to check the FPR. Vader once told me howto do it. The rubber hoses comeing up into the engine compartment are yer fuel hoses (most know that) one should be the return line, normally the smaller one. Take a C Clamp, and two wooden blocks (soto not pinch the hoses and have to replace them). After they are clamped down well, start up the car briefly. The fuel pressure should be significantly higher. If this is the case, it's the FPR. If not then i'd start looking at fuel pumps.

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89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-700R4 (Rebuilt) Too much done to actually list
-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)
-MSD 8.5 mm plug wires
-Problems every other day with the car (probably not a mod, but to me it sure makes a difference)