Timing Belt Tracking

[BlueDog]

After about 4000 miles of running after my rebuild I've noticed the timing belt has gotten narrower by about 1/8th inch. It's rubbing on the outboard lip of the tensioner pully.

Is there supposed to be a spacer washer between the tensioner and the engine block? Maybe I forgot to install it.

[greg lousy]

there's no washer

[BlueDog]

That being the case, I wonder how I get the belt to stop hugging the passenger side lip of the tensioner pully and track straight.

[bscutt]

Search the forum on this topic. I seem to remember several postings over the years about what injection pump bolts to tighten first, making sure all 4 bolts are present, worn pump shafts, intermediate shaft bearing wear, and surely more that I can't remember.

[greg lousy]

In my experience, timing belt tracking problems have been due to the IP sprocket being out of line. The belt will end up rubbing on the ridges of the intermediate shaft pulley (if its the type with outer rims) or maybe the tensioner. The IP mounting bracket is adjustable. Its held on by 6 or 8 bolts, and the relevant bolt holes on the bracket have eliptical holes, allowing for adjustment should the IP main shaft get out of line. I've always had to remove the IP to make the adjustment just because the screws are hard to reach... There's some under and to the center of the IP, then there's one or two to the left, then there's one in front by the alternator (this one has room for adjustment in the bolt hole). If the belt is rubbing and wearing on the inside, I would start by shifting the bracket as far as possible towards the driver's side. Then run with the belt cover off and see how the belt is tracking and readjust accordingly if you need to. If its still tracking to the inside, towards the engine, beyond the scope of adjustment on the bracket, you have excess wear on the IP mainshaft bearing. The technically sound advice would be to replace the IP, but you could also straighten it out by adding a washer or two to the IP bolt nearest to the radiator on the belt side of the IP. It isn't ideal, and the IP will not be flush with the bracket, but I have, on two occasions run for long periods like this, and the pumps have run well and airtight despite the mainshaft having excessive play

[greg lousy]

adding a washer or two between the IP and the bracket, I mean.

If you end up adjusting the bracket, tighten the front bolt, nearest the alternator first, to set the adjusted position. Also, to avoid removing and installing the timing belt multiple times, you can manually push the IP sprocket towards the camshaft sprocket to simulate timing belt tension after bracket adjustment, then check with a straight edge to see if its lined up with the camshaft sprocket.
I would also put a straight edge between these sprockets before adjusting anything to get a better picture of the tracking problem

[BlueDog]

So I put a couple straight edges on the sprockets. I don't see anything in the way of miss-alignment. I stood there watching as the engine ran and now see that the belt doesn't go around all the sprockets in a straight line. At one place the belt bumps over. I don't know if that's the right way to say it. Maybe the belt has a crooked area. Maybe the cam sprocket is bent. The belt just doesn't track in a straight line and I wish I could find the right words to describe it. The I/P mounting bracket is something I had't considered.

[82vdub]

As others have commented, a lot of this is likely coming from the IP installation. Contrary to common thought of why a belt tracks to one side, a belt will want to "climb" up the side of a pully, if the pully and belt aren't square to each other. Since your belt is riding towards the passenger side, I would say that your IP/pully is low on the drivers side, meaning that the passenger side of the IP pully is higher than the drivers side, so the belt wants to ride to the passenger side. To likely correct this issue, you have to raise up the drivers side of the IP (the high pressure side of the pump). Loosen the bolts and see if you can raise this end up and then check alignment. I've found that the adjustability of the IP brackets aren't so condusive to accomplish this, but if you play with it enough, you can likely get the belt tracking better.

[Fatmobile]

First loosen the tension on the belt and see how much play is in the sprocket.
If it moves side-to-side alot that's your problem.

You might still be able to raise the injector end of the pump by loosening the 2 bolts holding the pump bracket to the block.
These bolts are behind the pump so all 4 of the bolts holding the pump to it's brackets must be removed and the pump pulled away from the block.
I believe I've gotten to these 2 bolts without removing the belt or sprocket.

Lift the end of the bracket as high as you can (you'll have to figure out a way yourself) and bolt it there.

If that doesn't get it back on track your injection pump mainshaft bushing will need to be replaced.

I also worry about it destroying the intermediate shaft thrust ring by slamming it against the block,.. somewhat of an unproven theory on why those break.