Topic: fuel pressure
in Forum: All Vettes Discussion
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Lanoka Harbor, NJ - USA
Joined: 12/21/2006
Posts: 828
Vette(s): 1975 metallic blue coupe with t-tops,L48, t/t steering, black leather interior. 1990 L98, white/red leather interior, auto,a/c
just wondering if anyone can help with this. my 90 has fuel injection.
the pressure is supposed to be 42-47 punds. i have checked it and it
was 42. i know when you run it there may be a slight drop in
pressure for a second . anyone know what the limit is for the drop in
pressure? basically i am trying to determine if i have a weak pressure
regulator. i have recently installed a new fuel pump. thanks for any
help.
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Did you check the pressure with the vac. line connected to the regulator? That is "normal" pressure, or "idle" pressure. If you disconnect the vac. line from the regulator, the pressure should go to "Max". If it does not, the regulator is prolly stuck, or bad.
Also, check the pressure with it running, not just sitting with the key on.
Some regulators can burst the vac. diaphragm in them, and you'll wind up sucking fuel up thru the vac. line into the intake, making the engine run a bit rich.
I know my '85 pressures are not that high, but the later cars do run at a higher psi, and use higher flow-rated infectors.
If you do find you have to replace the regulator
, go with the adjustable one. Then you can fine-tune the pressure to match the infectors, and the needs of the engine.
Also, check the pressure with it running, not just sitting with the key on.
Some regulators can burst the vac. diaphragm in them, and you'll wind up sucking fuel up thru the vac. line into the intake, making the engine run a bit rich.
I know my '85 pressures are not that high, but the later cars do run at a higher psi, and use higher flow-rated infectors.
If you do find you have to replace the regulator


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Lanoka Harbor, NJ - USA
Joined: 12/21/2006
Posts: 828
Vette(s): 1975 metallic blue coupe with t-tops,L48, t/t steering, black leather interior. 1990 L98, white/red leather interior, auto,a/c
i didn't disconnect the vac line when i checked it. will try that
though. and checked with the engine running. i ran a can of the
pro type injector cleaner thru the lines and it feels it has better
response now. still has a slight unsteady idle. i am thinking
that my regulator might be on the weak side as the pressure is on the
low end. guess i will hook up the pressure guage and run and if it
drops below the 42 i will replace regulator. i would hope that an
adjustable regulator would be just the cover and diaphram to replace
and not the whole body. i know you can get just a new diaphram for the
one thats in there.
LIFETIME MEMBER #97
THE DYNAMIC DUO
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in Forum: All Vettes Discussion
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