Repair Pontiac Mid-size 1974-1983 Repair Guide

Diesel Injection Timing


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Fig. Fig. 1 Diesel engine timing marks and injection pump lines

For the engine to be properly timed, the marks on the top of the injection pump adaptor and the flange of the injection pump must be aligned. The engine must be turned off when the timing is set.


A magnetic pick-up tachometer is necessary for diesel work because of the lack of an ignition system. The tachometer probe is inserted into the hole in the timing indicator.

A special GM service tool, J-26987, must be used for this adjustment. These are available through most GM car dealers.

  1. Loosen the three pump retaining nuts using special tool J-26987.
  3. Align the mark on the injection pump with marks on the adapter and tighten the nuts to 35 ft. lbs.

Use a 3 / 4 in. open end wrench on the nut at the front of the injection pump to aid in rotating the pump to align the marks.

  1. Adjust the throttle linkage if necessary.