Fuel pressure only 36psi at idle
10-29-2006, 08:29 PM
#1
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Location: Post Falls, Idaho
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Fuel pressure only 36psi at idle
I put a gauge on the windshield and got 40 psi when i first started the car. As soon as i drove it it would go to 36 and stay there until i accelerated. It will go to the mid 40's once i get on it. Is this normal and should i check something else. I have an fmu for the supercharger but no inline pump hooked up.
10-29-2006, 08:31 PM
#2
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Location: TX
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I'm dealing with a weak fuel pump myself. 36psi isnt terrible. Mid 40s when you get the RPMs up is right where you want it. I'd say you are good to go with that. Pump might be a tad weak but I see no issues. You having an issue with the car?
10-29-2006, 09:16 PM
#3
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I have been dealing with a fuel pressure loss (0 for split second) at wot and over 5000 rpm. I took the inline pump out of the car and ran it. The psi with the inline pump was constant at 39 unless under throttle. Now it is 36 psi. I don't know what to check now. Fmu, intank pump & regulator?
10-29-2006, 10:07 PM
#7
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Might help to understand what the regulator does. It actually maintains one fuel pressure all the time but in reference to manifold vacuum and a gauge references off atmosphereic pressure. If the gauge references off manifold vacuum/boost the fuel pressure should never change. If it were not setup like this the high vacuum at idle would "suck" extra fuel from the injectors making them act larger. Under boost the pressure in the manifold would resist the fuel pressure and it would reduce the amount of fuel delivered.
10-30-2006, 09:48 AM
#8
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Sounds about right to me----should read around 43-46 with the vacuum hose off the regulator (simulating WOT at idle) and around 8 less with the hose on. I.e. if you're seeing 36 with the hose on that=about 44 with the hose off. Or am I wrong? JMHO
10-30-2006, 10:13 AM
#9
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Fuel pressure seems normal... 36psi at idle, jumps 6 to 8 psi (= 42-44psi) with the vacuum line off. The question is how does it hold up over 5,000rpm and the normal figures for acceptable fuel pressure at WOT will not apply, since he has an S/C and an FMU which raises the fuel pressure under boost.
He has another thread on the problem:
http://camaross.com/forums/showthread.php?t=480106
He has another thread on the problem:
http://camaross.com/forums/showthread.php?t=480106
10-30-2006, 10:15 AM
#10
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Another thought... the fuel pressure drops to "0". Have you checked you gauge/sending unit? Have you watched your fuel injector pulse width when the pressure drops to "0"? Does the pulse width drop to "0" as well?
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