Bosch In Line Fuel Injection Pumps

By 4 March 2017

All in-line fuel-injection pumps have a plunger-and-barrel assembly for each cylinder. As the name implies, this comprises the pump barrel and the corresponding plunger. The pump camshaft integrated in the pump and driven by the engine, forces the pump plunger in the delivery direction. The plunger is returned by its spring.

The plunger-and-barrel assemblies are arranged in-line, and plunger lift cannot be varied. In order to permit changes in the delivery quantity, slots have been machined into the plunger, the diagonal edges of which are known as helixes. When the plunger is rotated by the movable control rack, the helixes permit the selection of the required effective stroke. Depending upon the fuel-injection conditions, delivery valves are installed between the pump’s pressure chamber and the fuel-injection lines. These not only precisely terminate the injection process and prevent secondary injection (dribble) at the nozzle, but also ensure a family of uniform pump characteristic curves (pump map).

PE standard in-line fuel-injection pump
Start of fuel delivery is defined by an inlet port which is closed by the plunger’s top edge. The delivery quantity is determined by the second inlet port being opened by the helix which is diagonally machined into the plunger. The control rack’s setting is determined by a mechanical (flyweight) governor or by an electric actuator (EDC).

Control-sleeve in-line fuel-injection pump
The control-sleeve in-line fuel-injection pump differs from a conventional in-line injection pump by having a “control sleeve” which slides up and down the pump plunger. By way of an actuator shaft, this can vary the plunger lift to port closing, and with it the start of delivery and the start of injection. The control sleeve’s position is varied as a function of a variety of different influencing variables. Compared to the standard PE in-line injection pump therefore, the control-sleeve version features an additional degree of freedom.