Fuel Feed Pump for Mercedes-Benz Heavy-Duty Truck Engine
Also known as fuel transfer pump / gear-type fuel priming pump
OEM Part No.: A0040911401 (Replacement Part: A0040910501)
Applicable Models
Fits Mercedes-Benz Actros and Axor heavy-duty tractors / trucks, as well as Mercedes-Benz EvoBus coaches and buses equipped with OM501 and OM502 series diesel engines.
Function
It pre-pressurizes diesel fuel from the fuel tank and delivers it to the high-pressure common rail pump. As a low-pressure fuel supply component of the engine, it is a widely used spare part for Mercedes-Benz European heavy-duty trucks.
Working Principle of Gear-Type Fuel Priming Pump (Fuel Transfer Pump)
It is an external meshing gear pump and serves as the low-pressure fuel supply component for Mercedes-Benz OM501/OM502 engines. Relying on a pair of meshing gears rotating to complete oil suction and pumping, it supplies pre-pressurized fuel to the high-pressure fuel pump.
1. Structural Composition
The pump body contains a driving gear and a driven gear, with minimal clearance between the gears and the end face of the pump housing. The pump housing is fitted with an inlet port (suction chamber) and an outlet port (pressure chamber). The driving gear is driven by the engine timing gear to rotate, which in turn drives the driven gear to rotate in the opposite direction.
2. Operating Process
Oil Suction Stage
On the side where gears disengage, the volume between gear teeth expands and creates a vacuum negative pressure. Diesel fuel from the tank is drawn into the gaps between gear teeth under atmospheric pressure.
Fuel Transportation
As the gears keep rotating, the gear teeth carry diesel fuel along the inner wall of the pump housing from the suction chamber to the pressure chamber on the opposite side.
Pressurization and Discharge
On the side where gears engage, the space between gear teeth is continuously squeezed by meshing teeth, reducing the volume. Diesel fuel is compressed to build low pressure (typically 0.3~1.2 bar) and delivered through the outlet port to the high-pressure fuel pump.
The gears rotate continuously to cycle oil suction, fuel transportation and pressurization. The meshing surfaces of gears act as a seal, separating the suction chamber from the pressure chamber and preventing backflow of high-pressure fuel.
3. Role of This Pump in Mercedes-Benz Heavy Truck Fuel System
Pre-feeds fuel to the high-pressure common rail pump, ensuring stable low-pressure fuel at the inlet of the high-pressure pump and preventing cavitation and wear of the high-pressure pump.
Responsible for fuel delivery in the engine fuel circuit and fuel transfer prior to primary filtration.
Some models integrate a simple overflow valve: when pressure is excessive, the overflow valve opens and fuel flows back to the inlet side to stabilize the output pressure.
