WTF stumper question/guesses--200TDI broke down with STRANGEST symptom

[MountainD]

OK, so this one has troubled a lot of my friends and truth be known, I just got it to the house after breakdown so I don't know the answer. It is such an interesting one from a symptom standpoint, that it would be fun to see what you folks think and if you have a good TDI game .

Truck: 1991 200TDI.

What happened? My wife and dogs went up to the mountains, up an offroad trail and at the tip top of the trail before it becomes impassible from snow, the truck stopped. No odd sounds (like you can hear anything over a 200TDI anyways), no stuttering, just driving along and it's like I turned the key off. Boom. Off.

What I tried: Friend brought up 10 gallons of diesel. Thought it was out. there we go. Turn it over, it sounds like it is turning over pretty easy but there is some resistance but still feels a little light to turn over. Nothing. Not even an attempt to catch. Just turns over very strong. Exhaust doesn't even smell like diesel although air is being pushed through exhaust enough to blow a mask off the tailpipe.

Leave it for the night. In the wood, alone. Not ideal. Get there the next day loaded with tools as I know a thing or two about diesels now.
What I tried: Checked the fuel stop solenoid. Seemed obvious. Checked it and it worked find. Checked the voltage on the wire, even cranking, fine. Threw in a known good one...nothing changed. Changed the fuel filter. Changed the lift pump. No change. Nothing just cranking over. Everything looked good on the trail, just didn't run. Cracked the injectors. Spitting fuel. WTF?

Jabber came up and strapped me to get to a road. Towed it the rest of the way home.

Cloud looks nice. Screw you cloud.

Today, went to drive way. Cranked it over just cause. Removed inspection plate for IP and all bolts tight so didn't slip timing. Cracked injectors, they were doing this:

So I removed the rocker cover and saw a very bizarre thing:

So bizarre that I would like to see what you folks think before I dig in. Just cause I think it would be fun to see who gets closest.

Keep in mind-- IP is turning...cam is not... both run by the belt...

 

[SARTech]

Hmmm, Sheered Woodruff key on camshaft? Never seen that before but would explain what's going on.

 

[erover82]

Somehow sheared the camshaft on the red line?

Edit: SARTech's Woodruff key issue does seem more likely.

 

[rocky]

Time to remove the timing belt cover?

 

[jymmiejamz]

Must be a snapped cam or woodruff key. You wouldnt have fuel at the rail if the timing belt broke.

 

[Z.G]

Hmmm, Sheered Woodruff key on camshaft? Never seen that before but would explain what's going on.

I've seen it on a tdi. The keyway gets worn out and then it snapped. Extremely uncommon

 

[jymmiejamz]

I've seen it on a tdi. The keyway gets worn out and then it snapped. Extremely uncommon

I’ve seen it several times on the crank, but never the cam.

 

[Z.G]

I’ve seen it several times on the crank, but never the cam.

I was thinking crank, yeah never seen it on the cam

 

[meatblanket]

If the cam is not turning, there should be pistons hitting valves and bending pushrods. However, it looks like all of the valves are fully closed......

 

[jymmiejamz]

I was thinking crank, yeah never seen it on the cam

If it had happened to the crank woodruff key, the injection pump wouldn’t be spinning

 

[Z.G]

If it had happened to the crank woodruff key, the injection pump wouldn’t be spinning

Yeah I didnt' mean to say that was the cause, just commenting that I've seen a few snapped Woodruff keys, didn't notice he mentioned cam

 

[MountainD]

Cam snapping? Probably take a lot of force that cam doesn’t typically see, but I’m not ruling anything out!

key shearing? Have to say it was/is high on my list but looking at the key (I have 2 x200TDI disassembled in my garage to look at) it is pretty large with a ton of engagement. Just seems so....unlikely, but so do my conditions.

also, take another look at valve train video...all springs are same height...bent pushrods? Most likely, or one of my theories is that the cam gear bolt loosened so much that camshaft recessed into block so much that cam followers fell off cam lobes? I’ll look at other engines to see if even possible, but I can tell you the cam can recess further into block if gear isn’t attached. Then cam spins, timing belt spins, but cam misses drivetrain (still unlikely).
here is recessed cam on one engine I have:

seems every guess is unlikely or stupid rare... just my luck, lol. Better get one of my spare blocks/heads to machine shop pronto!

 

[jymmiejamz]

Well if the cam stopped spinning and the motor was rotated the push rods would have probably all bent

 

[Mffoster]

Was driving my 200Tdi recently on a highway at ~65 mph and suddenly lost oil pressure. Pulled over, checked usual things. Truck would not restart, had to be towed home. Began pulling things apart and turned out the end of the camshaft had snapped off right at the keyway. Only additional damage seemed to be 2 bent pushrods. Per Turner engineering that does happen occasionally because the cam pulley is so heavy and the stock bolt holding it on ends right at about the keyway, the weakest spot. Got my replacement cam and bits from Turner, used a longer bolt in the end of the cam. Checking end of injection pump didn’t help, since it still turned when cranking engine. Cam pulley stayed basically in place, so timing belt still ”looked fine” until removing front cover. should be able to rule out cam by removing valve cover and turning over engine - if valves move then cam shouldn’t be broken. Did you confirm you still have oil pressure? I have a gage in addition to the idiot light, so was pretty certain about the lack of oil pressure when it happened.

 

[MountainD]

Sounds like a legit reason. I'd put that at the top of the list knowing it is a "thing"... and I can tell you right now that the valves don't move. That is why I thought it may be missing the lobes (which I have never heard of, so that makes this the leader)

 

[MountainD]

Took off the front cover this week and figured out what happened although I am not fully sure in what order they happened. What seems most logical and actually one of my theories, was that the camshaft bolt loosened and allowed the cam to float back into the engine so that the camshaft gear was only partially engaged on the woodruff key. My theory was that the partial engagement sheared the key... but nope. It destroyed the entire nose of the gear! WOW! The good news is that the engine just stopped when that happened, no bad sounds or anything, just died. I'm not even sure I bent a pushrod. But at the same time, I'm not digging into that right now as I have bigger fish to fry in my garage.

For posterity...