The 2001 to 2004.5 Chevrolet and GM trucks with the LB7 Duramax diesel have an all too common problem with the fuel pressure regulator. The Duramax diesel engines incorporate a metering device that determines the flow of fuel to the CP3 fuel injection pump. The Durand Fuel Control Actuator determines the rate of fuel pressure provided by the fuel injection pump for proper engine operation.
The 6.6L Duramax Bosch 0928400535 applications:
All 2001 to 2004.5 Chevy Silverado 2500HD series trucks.
All 2001 to 2004.5Chevy Silverado 3500 series trucks.
All 2001 to 2004.5 GM Sierra 2500HD series trucks.
All 2001 to 2004.5 GM Sierra 3500 series trucks.
If the Bosch 0928400535 Fuel Pressure Regulator, MPROP, FCA, Fuel Control Actuator is not correctly functioning; this results in the Engine Control Module / ECM cannot determine the fuel flow rate supplied to the CP3 Fuel injection Pump. In most cases, people first know there is an issue when they have a hard start or no start issue because the MPROP will not allow the pump to build pressure to start correctly. However, by the time this symptom occurs, the truck has probably been delivering less than the genuinely desired amount of fueling for a while already as the FPR is a simple spring design that many times takes a rather slow death and not an immediate failure. The Engine Control Module / ECM uses the fuel control actuator to control the fuel pressure in the LB7 Duramax diesel. The Fuel Pressure Regulator - FPR is an electronically controlled solenoid valve. The ECM controls the amount of fuel that enters the high-pressure pumping chambers by opening and closing the Fuel Pressure Regulator based on demand. The Fuel Pressure Regulator is the device that controls the fuel pressure delivered to the injector rails to provide fuel delivery rates.
What are the symptoms of a failing 6.6L Duramax Duramax Fuel Pressure Regulator - MPROP?
No Start Condition
A Rattling Noise from the engine, which sounds like Fuel Knock.
You have decreased the engine power output level.
Engine operation is rough.
Engine RPM surging
A faulty fuel pressure regulator causes these symptoms. Replacing your 5.9L Cummins regulator can resolve your problem.
How to test if your Duramax Fuel Pressure Regulator - MPROP is working:
If you're experiencing hard start or no start issues, one easy way to confirm whether or not the FCA is causing the problem is to unplug it, thus eliminating any metering simply. The Fuel Control Actuator is a one-inch silver cylinder located on the backside of your CP3 fuel injection pump block. Presuming the truck starts, immediately turn it off as you will have full pressure running to the fuel rail, but at least you have reasonably high certainty that the FCA was causing the issue.