300tdi timing belt quandary

Dipodomys

Member
So I collected my "new" 90 at a southern California port about three weeks ago and drove it the 550 miles or so to Tucson, AZ. The vehicle is in excellent condition and had received a full service in the UK, including timing belt, prior to shipment, so I wasn't too concerned about any problems. The trip went well, but when I pulled into the driveway that's when I noticed that I was leaking something from the front of the engine. In the dark I initially assumed it was coolant, but upon further investigation (with my nose) I found that it was diesel fuel. Huh?

I did the usual online searches and found that diesel will leak from the bottom of the front cover if the forward seal on the injector pump has failed. That sounded just like my situation, so I set about securing the needed parts. I also learned that diesel fuel in the timing case will quickly ruin a timing belt, so I went ahead and ordered all of those parts as well, even though I knew the timing belt only had about 600 miles on it.

Upon cracking open the front end, I was confronted with the horror show that can be seen in the photo below. I was very close to disaster. The belt was largely destroyed, and the case was filled with debris, with long strings of disintegrated timing belt wrapped around everything and jammed behind the pulleys and gears. What a mess.

So putting in a new injector pump seal and timing components is fairly straightforward if you plan ahead and take it methodically. I've done timing belts and chains before, but never on a diesel, but it looks like just a few more steps are required related to the injection timing. No sweat. Read the instructions carefully, plan the job, and work methodically. Using one of those timing tool sets from RN, I inserted the pin in the flywheel housing and turned the crank until it engaged in the flywheel's slot. That's when I got stumped. If you look below at the second photo, you'll see a drawing from the 300tdi shop manual. The drawing indicates where the timing marks on the crankshaft and the cam gear pulley should be located when the timing pin is engaged and the No. 1 cylinder is at top dead center. The woodruff key on the crank should be positioned at 12:00, and the mark on the cam gear should be pointing at the arrow on the casing at about 8:00. Unexplainably, to me anyway, my marks aren't anywhere near those points. See the marked up drawing for where my marks land...the woodruff key on the crank is at 3:00 and the timing mark on the cam gear pulley is at 10:00. I have checked and rechecked this a dozen times...when the flywheel pin engages, this is where the marks are located.

How could this be? How could the engine even run like this? I can see how someone could have possibly put the cam gear pulley on incorrectly (it's possible, I guess, though it would take some effort). But the location of the crank key isn't something I can explain. Can anyone else? And of course the next question...what should I do? What am I missing?
 

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erover82

Well-known member
There are two timing notches on the flywheel. The pin should only drop into the larger one. They’re about 90 degrees out from each other, suspiciously similar to how much your crank pulley timing mark is off.

Otherwise the timing on the pump must be way off.
This video should help with understanding how it’s set.
 

Baldewin

Well-known member
Correct me if I'm wrong (that will happen anyway) isn't there two types or a later type timing gear regarding this type of wear?
 

Dipodomys

Member
There are two timing notches on the flywheel. The pin should only drop into the larger one. They’re about 90 degrees out from each other, suspiciously similar to how much your crank pulley timing mark is off.

Otherwise the timing on the pump must be way off.
This video should help with understanding how it’s set.
Thanks. I've watched and rewatched many of Mike's videos, and they are very helpful, and also entertaining! I'm planning to set my timing per his instructions in this and a couple of other videos he has on the subject, and have ordered the necessary tools to do so.

I'll recheck the timing mark question. I, too, note exactly how they are off, and have suspected that perhaps that might be the case. The problem is, none of the manuals or videos talk about their being two different marks. They are all very definitive in stating that you wait for the click and there you are. There are several pins in the RN timing kit. I'll try one of the other pins to see if it catches the other mark. If so, problem solved, and that would certainly ease my mind!
 

Dipodomys

Member
Correct me if I'm wrong (that will happen anyway) isn't there two types or a later type timing gear regarding this type of wear?
I'm not sure I follow. Can you elaborate? Are you saying that my timing gear might be "special"? I'd be perfectly satisfied with ordinary!
 

erover82

Well-known member
Correct me if I'm wrong (that will happen anyway) isn't there two types or a later type timing gear regarding this type of wear?

There are a few issues along those lines. This thread covers several of them. Worth a read.

 

DefendersNW

Well-known member
The flanged crank timing pulley was introduced to prevent belt walk. Yours is already the later flanged type, so replace with like for like.

Have a good look under the valve cover to make sure nothing made contact, but it sounds like you have have lucked out and only the IP timing slipped and not the cam. Clean everything, replace all the seals, address the IP leak, setup cam/crank first, install IP, set timing with cam/crank position first - then IP - then tensioner, run it through a couple revolutions by hand, loosen and set again.
 

Dipodomys

Member
Thanks. I've done all of the above and it has all come together nicely. I dialed in the timing with a dial gauge and it is now spot on. In conversations with Mike at Britannic Restoration, a common problem with these engines is that people overtighten the timing belt. Doing so pulls the timing case out of alignment, which causes premature wear of the timing belt (or destruction of the belt, as was the case with mine) and can also cause off-center wear on the front seal of the injection pump, causing rapid failure. I think that's what happened to mine, and it explains why my timing case became a diesel fuel aquarium and why the timing belt got eaten along its forward edge. My guess is that whoever installed the timing belt in the UK before my vehicle was shipped cranked hard on the tensioner and figured that was good. More is better, right? It's supposed to be 11 Nm only, which doesn't seem like much, so I expect a lot of folks opt to pour on the torque. Not good.

That's my working theory, anyway. Time will tell!
 
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