2000 Silverado 5.3L fuel pressure still low after new pump I replaced the fuel pump (AC Delco OEM)…
2000 Silverado 5.3L fuel pressure still low after new pump
I replaced the fuel pump (AC Delco OEM) and the new pump made only a slight difference and pressure is still out of spec. The new pump pushes about 2psi more pressure and draws 2amps less.
Old pump: 52psi key On / engine Off 48psi at idle 56psi at idle when you pull the vacuum line from the regulator Amp draw 8.5amps
New pump: 54psi key On / engine Off Flutters between 48-50psi at idle 58psi at idle when you pull the vacuum line from the regulator Amp draw 6.3amps
Fuel pressure regulator vacuum line is dry and no obvious signs of failure / fuel leakage and also see the readings above with the FPR vacuum line removed.
Measured the voltage drop for each the power and ground circuits and that checks out as well. Voltage drop is ~0.1v on the ground and ~0.5v on the power with the truck running. Battery only (i.e. not running) ~0.1v on the ground and ~0.4v on the power. Measurements taken from the battery post to the pump connector. Pump is also getting 14v while the engine is running (~14.6v at the battery).
Removed the fuel filter and blew out the supply line from the pump back to where the filter would be then switched sides and blew out from the supply line at the rail to where the filter would be and it did not make any difference. The fuel filter was changed about 2 months prior to the new pump in an effort to fix the low fuel pressure but did not make any difference.
So all that and the fuel pressure is still lower than the spec. of 55-62psi key On / engine Off.
What should I try next?