Rabbit Pickup L4-1588cc 1.6L DSL SOHC (1982)
Fig. 15 Plunger & roller
Input-shaft rotation is transferred to the distributor plunger by dogs on the input shaft and cam plate meshing with a yoke, Fig.15.
By virtue of the roller ring and cam plate, whose surface rides on the rollers, the input shaft's pure rotation is converted into rotary-reciprocating
motion. The plunger is set into the cam plate with its cylindrical fitting piece, and its position relative to the cam plate fixed by a lug.
The plunger is forced up towards its top dead center position by the cam surface, two symmetrically arranged return springs force it back down again
towards its bottom dead center. These springs are backed by the distributor head and act on the plunger by way of a spring link. In addition, the springs
prevent the cam plate from separating from the rollers under high acceleration. So that the plunger is not displaced from its centered position, the return
springs are matched precisely to each other.
Cam Plates and Cam Forms
Fig. 15 Plunger & roller
Besides driving the distributor-pump plunger, the cam plate, Fig. 15, also influences fuel-injection pressure and duration. The decisive criteria here are
cam stroke and lift velocity. These factors must be individually tailored to combustion-chamber configuration and type. For this reason, a special cam
plate surface is developed for each engine type, and is mounted on the cam plate's end face.
Because the cam-plate surface is specific to a given engine type, it is not interchangeable with those of injection pumps for other engines.
Pump Assembly
The distributor head, plunger and control spool are so precisely fitted to each other (actually lapped in) that they seal even at very high pressures.
Small leakage losses are nevertheless inevitable, as well as desirable from the standpoint of plunger lubrication, and they are designed into the assembly.
For this reason, only the complete pump assembly may be replaced - never the plunger, distributor head or control collar separately,
