Fuel PSI drops on boost??
04-26-2002, 08:33 AM
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Fuel PSI drops on boost?? --5# ATI Procharger on 2001 SS--
I have a drop in fuel pressure from about 70 PSI, which is about what I see at idle and cruise, to about 55 PSI at 5500 RPM's.
I have the vacuum line of the FMU tapped into the brake booster, as per the ATI tech I spoke to. The ATI tech also stated that a drop in fuel pressure is normal up to about 4500RPM and after this point is where the pressure should spike to 90PSI?? Is this correct??
Even with the needle valve on the FMU full rich the fuel pressure drops to about 55PSI at 5500RPM?? There are no kinks in the lines. Does this sound like a bad fuel pump??
Any input would be greatly appreciated,
Thanks Guys, Angelo
I have a drop in fuel pressure from about 70 PSI, which is about what I see at idle and cruise, to about 55 PSI at 5500 RPM's.
I have the vacuum line of the FMU tapped into the brake booster, as per the ATI tech I spoke to. The ATI tech also stated that a drop in fuel pressure is normal up to about 4500RPM and after this point is where the pressure should spike to 90PSI?? Is this correct??
Even with the needle valve on the FMU full rich the fuel pressure drops to about 55PSI at 5500RPM?? There are no kinks in the lines. Does this sound like a bad fuel pump??
Any input would be greatly appreciated,
Thanks Guys, Angelo
04-26-2002, 09:39 AM
#3
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Re: Fuel PSI drops on boost?? possible bad fmu -
possible kink in fuel line - seen by another user
possible bad vacum/boost source -
possilbly your inline pump is not kicking on -
<small>[ April 26, 2002, 09:40 AM: Message edited by: Blackbird ]</small>
possible kink in fuel line - seen by another user
possible bad vacum/boost source -
possilbly your inline pump is not kicking on -
<small>[ April 26, 2002, 09:40 AM: Message edited by: Blackbird ]</small>
04-26-2002, 09:55 AM
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Re: Fuel PSI drops on boost?? Thanks for your input...I guess I''ll be calling ATI back if I get no resolve with rechecking everything. <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
04-28-2002, 09:09 AM
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Re: Fuel PSI drops on boost?? here is how ati had me (I am the kinked fuel line) checking things.
to check fmu:
take allen bolts off of top cover
remove cover
(there will be a big washer looking thing, then rubber diaphram, then another washer.
IF there is gas ABOVE the diaphram (very top side just below the cover you remove) then the rubber diaphram has a hole in it. if no gas above the rubber diaphram then it's fine.
to check in line fuel pump:
have someone watch your fuel pressure
on the bottom of the fmu is a braided fuel return line,
kink this line SHUT with a pair of vise grips and if the fuel pressure gauge pegs then the ati pump is good.
after checking all of that and talking to ati HOURS I found it was a kinked line!
hope this helps.
to check fmu:
take allen bolts off of top cover
remove cover
(there will be a big washer looking thing, then rubber diaphram, then another washer.
IF there is gas ABOVE the diaphram (very top side just below the cover you remove) then the rubber diaphram has a hole in it. if no gas above the rubber diaphram then it's fine.
to check in line fuel pump:
have someone watch your fuel pressure
on the bottom of the fmu is a braided fuel return line,
kink this line SHUT with a pair of vise grips and if the fuel pressure gauge pegs then the ati pump is good.
after checking all of that and talking to ati HOURS I found it was a kinked line!
hope this helps.