Fuel Pressure
 

I put a fuel pressure gauge on the schrader valve, and it read ~15psi at idle, I put it on another car and it read around 40psi so I know the gauge is fine, but my question is would this be a bad fuel pump, or something else? The car holds pressure after its shut off. Its an LT1 by the way.

RE: Fuel Pressure
 

hey,
to check if you have a bad fuel pump or not, connect the guage to the valve , then swtich ignition on but dont crank the engine. it should be between 40 and 45 psi,get someone to do that while you are at the guage,when the car starts it wil drop as pressure will be lost to injectors.

RE: Fuel Pressure
 

Thanks for the reply. I did that heard it prime for 2 seconds or so, and there was no pressure.

RE: Fuel Pressure
 

Also test the pressure regulator. Pump could be good, but regulator could be bad. Regulator is cheaper and much easier to change than the pump.

RE: Fuel Pressure
 

How would I go about testing the pressure regulator?

RE: Fuel Pressure
 

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FUEL PUMP & PRESSURE REGULATOR TEST:

1) Connect a Fuel Injection pressure gauge (available from most part stores) to the test port on the FI rail (similiar to a tire valve). Be carful as fuel under pressure may spray out.

2) With the key ON & engine OFF (cycle the key ON-OFF several times as pump only runs for 2 seconds) the pressure should be 41-47 PSI. (If NOT: weak pump, dead pump, or no power to pump)

3) Turn key OFF, pressure should NOT drop more than 1-2 PSI and then hold steady. (If NOT: fuel line leak, injector leak, regulator leak, fuel pump check ball leaking)

4) Let engine idle, pressure should drop 3-10 PSI from the reading in step 2. ( If NOT: bad pressure regulator, vacuum leak to pressure regulator.

5) WOT (car accelerating at full throttle, pressure should hold @ 41-47 PSI. Good to have two people, one to drive and one to watch gauge (If NOT: dirty fuel filter, weak pump, bad pressure regulator)

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RE: Fuel Pressure
 

Thanks for that, it must be the pump since when I turn the key to the on position and the pump primes, I don't get hardly any pressure.

RE: Fuel Pressure
 

dont forget the fuel filter clogs the fuel line when its dirty, its better to change that first before spending $ on a pump and labor, as you might change the filter anyways, keep us posted

RE: Fuel Pressure
 

I changed the filter about a month ago so its probably not that, I'll be changing the pump within the next 1-2 weeks so I'll let you guys know if its fixes it.