I've been reading up on bumping the timing and in some cases people say their timing had slipped. I was just curious, isn't the whole contraption gear driven off of the crank shaft? I would think this would be a pretty closed loop system. How does the timing "slip"?

 

The Injection pump gear is not keyed, it is a "Tapered fit" and the torque of the nut holds it on. Sometimes they will slip.

 

Apparantely, they didnt tighten the nut enough from the factory...therefore, it tends toslip over time.

 

Both trucks I've timed had the lockwasher smashed totally flat. Probably wasn't doing much to help keep things tight.

 

Whenever the nut is removed to set the timing, be sure to spray the shaft with a good brake cleaner, that leaves no film at all, before the nut is reinstalled and torqued. If you don't, you will be in there again doing it all over. The nut will not hold up to heavy rpm's.

..Preston..

 

QD Contact Cleaner (for electrical contacts) is what Cummins says to use. It dries lighting fast - like 3 seconds if the engine is warm. Even in 30 degree weather the stuff is gone in 5 seconds.