In diesel engines with four to twelve cylinders, (figure 1) the in-line injection pump should pump the diesel fuel in exactly measured amounts and at predetermined times under very high pressure to the single nozzles. The use of this type of pump is important in large-capacity engines with a higher fuel necessity.

The driving force is supplied by a camshaft chain or a spur gear. The fuel is sucked in by a fuel booster pump unit. This consists of at least the piston pump, can however, depending on the version, also contain the pre-cleaner and the manual pump. The piston-pump is driven by an eccentric on the camshaft of the fuel injection pump. Depending on the construction it boosts with each- or every second stroke. The fuel is boosted through a simple- or double filter into the upper part of the fuel injection pump.

The in-line injection pump typically has, per engine cylinder, one pumping element. The piston is driven by the camshaft of the fuel injection pump by roller tappets. These pump the fuel through a pressure reduction valve individually at the specified point into the injection lines. Whereby, the injection amount is determined by the specified torsion through a common gear rack (fuel control rack).

In older pumps, (figure 2) the fuel control rack is connected with the accelerator pedal as well as with the centrifugal governor (on the left). With newer pumps (figure 1) the fuel control rack is driven electrically. No matter whether full power is given or not, the fuel control rack is drawn back if a certain maximum RPM is exceeded. In addition, steady idling must be also be provided for. In older pumps the injection advance device (on the right) is responsible for an earlier fuel delivery at higher RPMs, in the newer ones the cylinders of the individual pump elements are shifted electrically.

The in-line injection pump (below) is lubricated in the area of the camshaft by a fixed oil filling or by the engine oil cycle. The lubrication of the high-pressure pistons (on top) takes place as with the distributor-type fuel-injection pump, exclusively through diesel fuel. The construction of a diesel in-line fuel injection system does not efficiently prevent an opposing rotational direction of the crankshaft. This would be possible should kick-back occur when starting (similar to older single cylinder engines) or by towing in reverse gear, this however, would have fatal results. e.g., the lubrication would not function. Therefore, engines which are threatened in this direction, have a camshaft with a very asymmetric profile. In the event of reverse running, the increase would be so slow that no injection pressure would be built up. 09/08

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