21 Nov 24

2000 Chevy Silverado LS extended cab (4Dr) with LM7 5.3 ltr gas engine. 4 Speed automatic transmission and has 87000 original miles.

It has a return fuel line and RPO code of EVA and a new Delphi Fuel Pump is # FG0407 . A Delco Fuel Pump is #19369915 (MU1613).

It will have "TCF" printed on the top of the pump

The fuel pump runs and I was able to drain old gas from the tank via the fuel line Schrader valve very quickly. There was plenty of fuel flowing.

Fuel Pressure Gauge reads 3-4 lbs of pressure at the fuel rail Schrader valve when the key is turned to "ON" and immediately drops off to Zero lbs of pressure.

Engine will crank as it should, but it will not start.

Replaced Crankshaft Position Sensor and the MAP sensor as needed based on OBDII trouble codes. Now it has No trouble codes at all. Cleaned MAF, also Throttle Body was cleaned and butterfly moves freely, Idle Air Control Valve replaced, Throttle Position Sensor moves freely. New PCV valve and Fuel Filter. It also has a new Delphi Fuel Pressure Regulator and it's not leaking fuel.

Could the Fuel Pump deliver plenty of gas but not develop sufficient pressure to run the engine?

I don't want to simply replace the fuel pump without knowing if it's really not working. It was replaced in 2015 with a Bosch Fuel Pump and has only about 2000 miles on it since then. The truck is not driven a lot. It had old gas in the tank. Very Yellow color. I removed about 15 gallons of this old fuel and it's reading less than 1/4 tank now.

I'm open to any suggestions.

Thanks

Keats

Arizona