TPI fuel pressure

[Marteney, Steven J.]

Two things from me:
1)  Didn't mention, on purpose, that my friend's IROC with the steady
reading has a brand-new fuel pump.
2)  Did the tape-to-the-windshield thing this morning.  Okay.  As temp came
up, meter became more steady, still a little jitter.  Certain times the
gauge would increase on a throttle hit.  Other times it would decrease.  The
one REAL HARD pass I did (don't tell the cops) put the gauge at 40psi
steady.  It was typically pulsing up around mid-40's to 50.
 
That's another thing that is pissing me off.  This $^%$&% AFPR seems to
change pressure day to day.  Or maybe it's the fuel pump or regulator that's
changing.  Thinking of going back to my old stock reg cap and being done
with it.
 
Steve

-----Original Message-----
From: Bja1078 at aol.com [mailto:Bja1078 at aol.com]
Sent: Tuesday, February 27, 2001 12:23 AM
To: gmecm at diy-efi.org
Subject: Re: TPI fuel pressure




hi,  I think this might help. First, I'm a GM drivability tech. guage 
fluctuation is normal, and will very depending on the vehcile its connected 
for a few reasons and here are just a couple. #1. pulsing injectors, fuel 
pumps have a smooth output even when they are going bad! #2 air in the 
pressure guage line will dampen the fuel pressure pulses, If the guage has
an 
air bleed and this is utalized which I don't for this very pupose, the guage

will fluctuate alot, so some techs going from one car to another and one car

multiple times without purging all the fuel out of the guage line will
notice 
this fluctuation. #3 some vehicle are equipped with a inline dampener to 
help eliminate this pulsing, and this can also alter reading form one
vehicle 
to another.  they do this because of pump whine, caused by the pulsing of
the 
injectors. if your are concerd with a lack of fuel volume and pressure do 
this. tape your guage to the windsheild and go drive the vehicle. smash the 
gas and hold it. 
pressure should increase and become steady, i.e minor fluctations not 
important, but it should not rise to say 48 psi and then fall with gas
peddle 
 smashed to the floorboard. tipically falling indicates a bad pump, but
don't 
over look the regulator than can be trickey like that. 
hope that helps!! 

-Brian 


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