How-To: Replace a MKIV ALH Diesel Injection Pump without Changing the Timing Belt

BobnOH said:

Yes I know this is a 5 year old post, but I want know- Were you able to do this with the tensioner in situ? I would think anyone who is very familiar with the belt replace procedure might be able to do this, but for most of us who have only done 1 or 2, I'd recommend following the final steps of the procedure. Cam locked, crank locked pump pinned, tension with pulleys freewheel.

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You can totally do it with tensioner in place. There is no reason to have to remove it. That would make things much harder and unnecessarily way more work.

Once the tensioner is loosened and rotated counter clockwise to its loosest position, the cam sprocket is removed and belt stays in place. At that point, the IP sprocket comes off and IP removed. There is plenty of slack in the belt to get the IP back in place and redo the timing belt tensioning procedure. Setting the tensioner is a bit more to deal with since the motor mount bracket is in place, but other than that, easy sailing.

Tensioner ”in place,” yes. Tensioner still set (which is how I was reading it), not so much.

BobnOH said:

Yes I know this is a 5 year old post, but I want know- Were you able to do this with the tensioner in situ? I would think anyone who is very familiar with the belt replace procedure might be able to do this, but for most of us who have only done 1 or 2, I'd recommend following the final steps of the procedure. Cam locked, crank locked pump pinned, tension with pulleys freewheel.

Click to expand...

Yes, I loosen the belt tensioner. The tensioner tool stays in place and rests against the back of the engine mount.

I just set the engine at tdc, paint mark pump sprocket to belt (this is so you get the pump sprocket back in the exact orientation), pin the pump, zip tie the belt to the cam sprocket, loosen pump sprocket bolts, loosen tensioner, remove pump pin. Then I work the pump sprocket off the hub and out from under the belt. Reverse for install. Just to note. The cam will not move unless you do something really dumb. I've R&R'd dozens of pumps using this method most of the time under 20 minutes including bleed and adjustments.