Replacing an Injection Pump

Hi All

Im new to the forum, and am about to change the DS4 pump on my truck..

The question i have is when removing the pump, after moving the motor around to TDC, can i just make a mark on the flange and bolt the new pump, into position, will the PCM then automatically make fine adjustments to the timing, or will it just retard the timing, also my truck has 85 000kms on it, would it be an idea to change the timing chain while im there, i dont know if it will have enough play in it to worry too much?

Thanks in advance

If all you are doing is replacing the pump, installing it in the same position as the old pump will retain the same timing and PCM response. There may be a slight timing increase, but rarely detectable or noticed. This would depend on how worn the old pump is, as a quicker pressure rise is slightly advanced timing. Usually, the reason for replacing the pump will make this completely oblivious. Replacing a worn timing chain has a more profound effect (if your pump is worn out, the chain is likely past due).

Retiming and completing the learn process is recommended to optimize the new pump. Many folks just replace and move on, w/o any adverse effects. I've done it both ways with mixed results. Much depends on the condition of the replaced and existing components.