I am in the process of changing the timing belt and tensioner on my 88 240dl. I have the belt lined up and when I try to do the 720* rotation the belt walks out (meaning that it begins working itself off the cam pulley toward the front of the car). I looked at the stepbystep volvo instructions and he noted the same issue, but no resolution.

Has anyone else had the same issue and figured it out?

Thanks,
Kags

 

There are only a couple of things that will cause a belt to run off a pulley. One is for the pulleys to be out of line. I would check carefully that the crank pulley is seated properly, likewise the cam pulley.
Also check to ensure the idler pulley is sitting perfectly flat against the cylinder block and that it's metal bracket is not warped. Pull it off the engine if you need to and use vernier calipers to measure height from mounting face of metal plate to edge of pulley in several spots. The idler pulley is usually the biggest suspect as it gets pried when removing belts, is never changed etc. It should ALWAYS be changed when a new belt is fitted, for this reason.
Another issue can be if the cam gear has any run out (or wobble). This is not uncommon as the cam gear can get knocked around when removing cam or cylinder head, or if you run without the belt covers on.
It only takes a tiny amount of runout or misalignment to make the belt run out.
On my engine however, the belt does run towards the front of the cam pulley, even after I pushed it back to the rear, so don't confuse that with it running forward, it's just finding it's own place.

Regards, Andrew.

 

In my case, I just reused my old tensioner pulley. It is not flush with the front of the engine. Instead, the top of the pulley is bent forward, but it works. I suspect all three pulleys (camshaft, intermediate, and crankshaft) are not aligned properly. If you can determine which pulley is out of alignment, you may be able to put a correctly sized keyed washer in back of the pulley. I was going to try to make such a washer, but other things in life took precedence.

Just out of curiosity, was your old tensioner pulley also bent?

Good luck!