First some background. 1984 300sd. I replaced the engine earlier this summer. Ran ok. Replaced the injectors with Monarch Injectors. Ran good for a while then lost power and was blowing white smoke. Adjusted the IP timing and everything was good again. Real good. Drove for about a week then found power falling off again and white smoke. Barely starts. Checked everything and the only that stands out is that the IP timing is off again. Very retarded.

What could allow the timing of the ip pump to change??? The only thing I can come up is the Chain tensioner.

This to me is a generally different type of complaint and unusual on these engines. I doubt the chain tensioner as its function when running is to take slack up on the portion of the chain not under load. How much correction in degrees did it drift off the last time?

If the 617 is like the 603, the IP sprocket has an advance mechanism. Maybe yours is sticking.

Sixto
87 300D

That would have been my other guess. Is that common?

I've never heard of one failing. Have you checked the chain for elongation? Is there a standard or offset key in the cam sprocket?

Sixto
87 300D

I agree with Sixto that the advance mechanism is a suspect but they do very rarely give problems. If the springs broke it would advance early not retard. I would suggest removing the Vac pump and check tightness of the center bolt holding the timing mechanism onto the pump drive shaft. The woodruff key on the drive shaft is narrow and designed to sheer in case of a pump jam up. If the bolt came loose it would start to chew through the key like an impact wrench and that would cause an increasing retard. The bolt was originally right hand but was changed to left hand so that if the key sheered it would undo the bolt and cut the engine, not tighten and break the bolt and/or timing chain!

Really the only other thing that could cause this is loose pump attachment bolts. Loose chain tensioner would not alter relationship between crank and pump sprockets.

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Beagle