Because in-line pumps like the PES4A are lubricated via the engine's oil circuit , regular oil changes are critical to prevent internal wear. Bosch PES4A Diesel Engine Manual | PDF | Fuel Injection
The PES4A operates through a synchronized camshaft that drives individual plungers for each engine cylinder. bosch pes4a manual
: A common control rack moves the helical notch on the plungers. This rotation changes the "effective stroke," adjusting how much fuel is sent to the injectors versus how much is bypassed. Because in-line pumps like the PES4A are lubricated