The CP3 is a Bosch high-pressure fuel pump that feeds the common rail on many diesel trucks, building fuel pressure of more than 20,000 psi for the injectors. Ram used it on the common-rail 5.9 Cummins from 2003 and on the 6.7 Cummins through the 2018 model year, and GM used it on Duramax engines up to 2010. It has a reputation for durability, and when it does fail the usual signs are hard starting, low rail pressure codes such as P0087 and loss of power.
What a CP3 pump does
A low-pressure lift pump supplies fuel from the tank through the filters to the CP3. The CP3, driven by the engine, pressurizes that fuel and sends it to the common rail, where the engine computer controls rail pressure and fires each injector electronically. Because the injection pressure is so high, the CP3 depends on clean fuel and a steady supply from the lift pump.
Which trucks use the CP3?
| Engine | Pump |
|---|---|
| 5.9 Cummins common rail (2003-2007 Ram) | CP3 |
| 6.7 Cummins (2007.5-2018 Ram) | CP3 |
| 6.7 Cummins (2019 and later Ram) | CP4 family |
| Duramax LB7 through LMM (2001-2010 GM) | CP3 |
Later engines moved to Bosch’s CP4 family, which drew attention for failures that can send metal through the whole fuel system. That history is a big part of why the CP3 is so often discussed.
Symptoms of a failing CP3
- Long cranking or hard starting, especially when hot
- Low rail pressure codes such as P0087 (fuel rail or system pressure too low)
- Loss of power or the truck going into a reduced-power mode under load; see limp mode
- Stalling, stumbling or rough running
- Metal debris in the fuel filter, a sign of internal wear
Many of these symptoms can also come from a weak lift pump, clogged filters, air in the fuel or leaking injectors, so check supply pressure and the filters before condemning the pump.
What damages a CP3
- Contaminated fuel: water and dirt wear the pump’s internal parts. Change fuel filters on schedule and drain the water separator.
- Low supply pressure: a failing lift pump starves the CP3.
- Running out of fuel or air in the system.
Replacing a CP3
When a high-pressure pump fails, debris can travel to the rail and injectors, so a proper repair checks the whole high-pressure side, not just the pump. For trucks that need a complete engine, the D&J Ready Run packages we carry include the fuel system: the 5.9L Ready Run for 2004.5-2007 Ram 2500/3500 and the 6.7L Ready Run for 2007.5-2018 Ram 2500/3500 each list a remanufactured CP3 injection pump, tested injectors, a new fuel rail and new high-pressure lines along with a remanufactured long block.
More on these engines: 6.7 Cummins specs, 6.7 Cummins problems, 12 valve vs 24 valve vs common rail and Cummins engines.
More guides: fuel filter · fuel pressure regulator · CP3 vs CP4 · diesel won’t start · bad diesel injector symptoms · water in diesel fuel.
Trouble codes: P0087 Fuel Rail Pressure Too Low · P0088 Fuel Rail Pressure Too High · P0089 Fuel Pressure Regulator Performance · P0191 Fuel Rail Pressure Sensor Range · P0190 Fuel Rail Pressure Sensor Circuit · all OBD2 codes.
Shipping is a flat $80.00 per order to US addresses, with 15-day free returns. Questions? Ask a parts specialist.