2003 Chevrolet Silverado Low Fuel Pressure

2003 CHEVROLET SILVERADO
179,000 MILES • 5.3L • V8 • 4WD • AUTOMATIC
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R69NFINE
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My Silverado set a CEL the other morning, pulled code, was for Knock Sensor #2. But when I went to pull it in garage it cut off, would not restart, just crank.So checked Fuel Pressure, only 40psi. So I replaced 2 Knock Sensors, harness, and fuel pump module(dealer parts). Drove it to work next day, was perfect, ran better all around. Set off on trip, went 300 miles, cutoff when stopped for gas, no restart just crank. Towed home, pulled Intermittent Crank Sensor Code, and rechecked fuel press for fun, KOEO 50Psi, KOER 47psi, unhooked regulator 52psi. So I grabbed a CKP sensor and fuel regulator. No more code, running great, still same fuel pressure, why? Fuel Trim -.8 to 3.5% short or long. Looks good on scanner runs great, im stumped.
May 23, 2015 at 12:48 PM
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WRENCHTECH
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What is the 8th digit of the VIN#?
May 23, 2015 at 9:37 PM
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WRENCHTECH
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OK, it looks like the "Z" motor is not an option in that truck so the pressure spec is 55-62PSI.
It has to remain within that range at all times. If it can't produce those numbers, then the pump has to be bad. You probably should check the inside of the tank for any type of contamination that could be damaging the pump.
May 23, 2015 at 9:42 PM
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R69NFINE
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Vin T
May 23, 2015 at 9:45 PM
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R69NFINE
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Tank is clean, inspected when installed pump, any other ideas
May 23, 2015 at 9:46 PM
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WRENCHTECH
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Other ideas? I already told you that you have a bad pump, assuming your gauge is accurate which could be questionable.
May 23, 2015 at 9:53 PM
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R69NFINE
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A bad dealer pump out of the box? I removed new fuel filter this am, pressure 50 KOEO, 47koer, but went 60 psi with regulator unhooked. Any thought on that?
May 23, 2015 at 10:14 PM
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WRENCHTECH
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If the pump is capable of over 60 PSI and the regulator is what's pulling the pressure down, then obviously the regulator is to blame. It's always possible that you got a regulator for a "Z" engine which runs at lower pressure. Also make sure you have changed the fuel pump connector to the updated version from the square one. There is an issue with voltage drop on the old style.
May 23, 2015 at 10:44 PM
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