Pump, Fuel Injection, High Pressure: Operation
WARNING: This page is about a different car, the 2017 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
- The timed fuel injection pressure pump is driven by the crankshaft through a toothed belt and sprocket arrangement. The pump must be supplied fuel through the low pressure circuit with a minimum pressure of 3.5 bar and a minimum flow rate of 160 liters per hour to ensure correct operation. This supply is achieved by means of the low pressure electric fuel pump integral to the fuel pump module submersed within the fuel tank.
- The three pump pistons are operated by the rotation of a triangular-shaped cam integrated with the pump input shaft. This cam causes the movement of the three pistons in succession, through the movement of a mechanical interface (tappet) between the cam and the base of the piston. The contact between the cam and each individual tappet is maintained by means of a spring.
- Each pumping unit is equipped with a plate type intake valve and a ball type supply valve. All three delivery valves of the pumping elements are united inside the pump and deliver the pressurized fuel to the common rail (manifold) through a single high pressure tube. A feature of this pump is that it is lubricated and cooled at the same time by the diesel fuel circulating inside it, via special ports.
- The fuel quantity solenoid on the pump adjusts the supply pressure at the pump intake as needed to compress only the amount of diesel fuel needed to reach the pressure targeted by the Powertrain Control Module (PCM).
- The pump is driven by the engine at a rotation speed equal to 2/3 (4 volts) and 25/43 (2 volts) of that of the actual engine, by means of a toothed belt transmission. The timing and injection duration are, in this injection system, tasks of the electronic control system; this pump only carries out the task of permanently maintaining the fuel contained in the manifold at the requested pressure level.