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96 GMC Suburban Fuel Pressure problem

1674 Views 6 Replies 5 Participants Last post by  Motor City Rick
I have a 1996 GMC suburban 2500 7.4 vortec that has a miss at idle. I have replaced the FPR, spark plugs, wires, Cap, and rotor and its still misses. when I connect my pressure gauge and turn the key on it jumps to around 45psi and holds but when I turn it off it falls back to around 25psi. could it be a faulty FPR or if it was the rubber hose on the fuel pump shouldn't I hear the gas running back in the tank? any help would be greatly appreciated.
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Sounds like low pressure, should be between 56 and 62 psi, block off return line, retest...deadhead pressure should be above 70 psi. From what you described, my first two thoughts would be fuel pump or line restriction. Then possible leaky injector...but I would get the pressure where it belongs before I worried about injectors. Blocking the return takes the fpr out of the equation.
Warning... Above 75psi is rough on the be ready to kill pump power or release return will build quick if it does actually build. (I'm expecting, it doesn't though)
Where would I block it at? at the engine or on the line its self?
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