Bosch CP3.3 Fuel Transfer Pump – Genuine High-Pressure Common-Rail Supply Solution

The Bosch CP3.3 transfer pump (commonly referenced with OE variants such as 0445020089, 0445020013, and 0445020043) serves as the critical low-pressure fuel supply foundation for high-performance common-rail diesel systems. As the dedicated feed pump paired with the CP3 high-pressure injection pump, this unit is responsible for drawing fuel from the tank and delivering a consistent, aerated-free volume to the high-pressure pumping plungers. For workshops and parts distributors specializing in Cummins ISB/QSB, Duramax, and heavy-duty off-highway engines, the CP3.3 transfer pump is not merely a replacement component but a vital determinant of fuel system reliability, injector longevity, and overall engine uptime.

The versatility of the Bosch CP3.3 transfer pump makes it a stock-keeping essential for diesel specialists. It is predominantly found on Cummins 3.3L, 4.5L, and 6.7L ISBe, ISDe, and QSB series engines (CM850 and CM2150 control systems), as well as Duramax LBZ and LMM platforms . Furthermore, the pump is OE-matched to Dongfeng Renault DCi11 and Kamaz 11.8L V8 heavy-duty engines . In the off-highway sector, it supports Liebherr construction machinery and various agricultural tractors requiring sustained high-load performance. Its radial piston architecture tolerates the extreme temperature fluctuations found in both on-highway trucking and stationary generator sets, making it a staple for repair shops that service a mixed fleet of vocational vehicles and industrial diesel equipment .

Correct installation is the primary determinant of this pump's service life; improper handling is the leading cause of premature warranty claims. The pump must never be "dry-run"-the gear pump requires at least 60 mL of clean diesel injected into the inlet port prior to installation to ensure initial lubrication and avoid scoring the pump gears . Installation does not require camshaft timing alignment due to its non-timed function; however, strict adherence to torque procedures is non-negotiable: the mounting bolts must be tightened to 25–35 N·m and the drive gear nut to 100–110 N·m, preferably in a crisscross pattern to prevent distortion . After mechanical mounting, the system must be fully primed using a hand primer or auxiliary lift pump until fuel free of bubbles exits the filter outlet-only then should the high-pressure lines be connected. 

Investing in a genuine Bosch CP3.3 transfer pump offers measurable long-term value for diesel repair operations. This pump acts as the "gatekeeper" of fuel quality, filtering contaminants before they reach the high-pressure plungers and injectors. In the field, the CP3.3 is notably resilient against low-lubricity biodiesel blends, but it is susceptible to aeration-microscopic air bubbles entering via suction-side leaks. These cause the gear pump to cavitate, leading to loss of rail pressure and erratic engine performance (P0087 low rail pressure codes) . By replacing a worn or internally leaking feed pump, service centers can restore rail pressure stability, eliminate hard-hot-start complaints, and reduce injector strain. The pump's straightforward rebuild process and wide aftermarket support, including "stroker" variants for high-HP builds, ensure that whether maintaining stock work trucks or upgrading fleet vehicles, the CP3.3 remains a cost-effective solution that significantly lowers the risk of catastrophic high-pressure system failure .

Q1: How to confirm compatibility before ordering?
A: Cross-check your original OE number (0445020089 / 0445020013 / 0445020043) and connector type. The CP3.3 uses a 24V AMP Superseal connector with 2.8Ω coil resistance. It is not interchangeable with CP4 pumps without a harness conversion and ECU reflash.

Q2: What symptoms indicate transfer pump failure vs. high-pressure head issues?
A: Failing transfer pump shows prolonged cranking, warm-start surging, and inlet pressure below 4 bar under load. Unlike plunger failure, it rarely sends debris downstream, making it a less costly repair.

Q3: Is hand-priming sufficient after installation?
A: Hand-priming fills the filter and inlet, but we recommend using a vacuum pump on the return line to fully evacuate air from the SCV chamber-air pockets cause erratic rail pressure on first startup.

Q4: What is the expected service life of this pump?
A: Bosch does not specify a fixed mileage interval. With regular fuel filter changes (15,000–20,000 miles) and water separator maintenance, these pumps commonly exceed 500,000 miles in highway applications.

Q5: Does the "Stroker" upgrade affect the transfer pump?
A: The stroker mod modifies the high-pressure head (stroke increase), not the transfer section. However, high-flow builds demand a healthy CP3.3 to supply the extra volume needed at high RPM.

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