190D timing chain replacement woes.
 

I also posted this over on benzworld so sorry if you see it in both places.

I finally got enough time to replace the timing chain on the used 190D I picked up back in March, well everything was going well until the temp link between the new and old chain went over the Injection pump gear and some how the chain jumped off the injection pump sprocket.

Well to shorten the story I ended up finally getting the new chain fished all the way through the engine but the injection pump timing is off by about ~25°. It is currently around 10° BTDC instead of 15°ATDC.

Any tips on the best way to get the pump timing back where it needs to be, hopefully without removing the injection pump?

Thanks,
Chadd

Set the cam to #1 TDC, confirm the crank is at TDC or within a couple of degrees. Advance the crank to 15*ATDC, remove the vacuum pump. Fashion a strip of thin metal wider than the chain and just longer than the length of chain that engages the IP timing sprocket. Remove the chain tensioner, turn the cam slowly clockwise to allow slack around the IP timer. Slip the strip of metal between the chain and the IP timer. Remove the plug (17mm wrench) on the side of the IP, turn the IP sprocket until the timing lug is centered in the hole. Ideally, you have an IP lock to positively confirm the position of the timing lug. Remove the strip of metal, engage the chain on the IP timer. Turn the cam counter clockwise to take up the slack. Prime the tensioner by immersing it springy end down in engine oil, push down on the tensioner repeatedly until it feels as firm as it's going to get. A dozen strokes should do it. Install and torque the tensioner, I've had no problem reusing the crush washer. Turn the crank two revolutions to confirm cam and IP timing; crank at TDC, IP at 15*ATDC. Fine tune IP timing if necessary by loosening the 3 bolts (13mm wrench) around the vacuum pump and 1 bolt in the aft end bracket then turning the 8mm hex accordingly. Tighten the 4 bolts. Install the vacuum pump; I've had no problem reusing the metal gasket once.

Sixto
87 300D

Thanks for the reply.

Do you need to remove the cam timing gear to be able to get enough slack to get the chain off the injection pump? Or will it give you enough slack with just the tensioner out?

There should be enough slack with the chain around the cam sprocket. If not, zip tie the chain to the cam sprocket, remove the upper chain guide and pull the sprocket from the cam (mind the woodruff key if there is one). Don't lose cam timing at this point!

Sixto
87 300D

Thanks for the help, I will give it a shot. I did get one of the locking pins ordered so hopefully it will be here in a day or two.

Thanks,
Chadd

One more question I have that you may be able to help me with is, regarding cam timing. I can't get the line on the cam to line up exactly with the mark that is on the #1 bearing cap while the engine is at #1TDC. The best I can do is either 5° before or 10° after TDS. This is with indexing the cam chain one tooth in either direction on the cam gear.

Any ideas here?

Thanks,
Chadd

Appears your chain has stretched beyond spec :/ Offset keys to 3* are available to bring 617 cam timing back into spec, not for a 60x. Regardless, get your IP timed as close to spec as possible without touching the 8mm hex. Get the engine running to confirm. Then roll in a new chain and fine tune IP timing. If you're able, borrow/rent an A-B timing light to make quick work of setting IP timing.

Sixto
87 300D

This is a brand new chain.. Installing the new chain is what started this whole mess.

Oh, shoot, that's right! I lost track of why you're doing this in the first place. are you taking the average or median of a half dozen or so measurements? are you using the correct cam alignment marks? Are you checking cam timing with the tensioner primed and torqued in place and all chain slack between the crank and cam? Are you sure the crank pulley pointer has never moved? MB uses an adjustable pointer, heaven knows why. IP timing won't have anything to do with cam timing.

Sixto
87 300D

Yep I have done all of the above.

I Just got in from the garage where set up a dial indicator similar to what they call out in the manual for checking cam timing. These are the two readings I come up with with chain index one tooth either way.

One position I ended up with 2mm valve movement @ ~7-8° ATDC and the other position I didn't get 2mm valve movement till @ ~17-18° ATDC. The manual says you should see 2mm of movement @ ~11-12° ATDC.

As far as the pointer I have no idea if it is ever been moved. What is the best way to check for TDC? It is easy on a gas engine, just remove a plug and put a dowel rod in there. But I am not sure on a diesel.

Thanks,
Chadd

It's not very different conceptually - pull a prechamber and set a dial gauge on the piston - but a lot more work. Rube Goldberg might suggest instead removing a valve spring and setting a dial gauge on the valve spring. There's a hair's width of a gap between the piston crowns and valves in a 60x that there's no risk of dropping the valve if the piston is anywhere close to TDC.

Sixto
87 300D

Do you have a reference image of a cam sprocket? Maybe your cam sprocket is worn enough to throw off cam timing. IIRC there's a TSB for early 602s with guidance on checking the sprocket for excessive wear. Basically the teeth get pointier as the sprocket wears.

Have you seen these documents?

http://www.w124performance.com/docs/mb/OM60X/OM60x_Timing_Chain_TSB.pdf

http://www.w124performance.com/docs/mb/OM60X/OM60x_Timing_Chain.pdf

Sixto
87 300D

Nope no image, the sprockets very well could be worn this car is over 200k. The cam sprocket doesn't look too bad but it is hard to tell.

Thanks,
Chadd

No offense to Sixto, I would seriously consider his opinions.

Personally, pulling the prechamber on an early aluminum MB diesel head should be avoided.

Put a pressure gauge on the cylinder in question to determine TDC or do the required math. (72* for 5 cylinder or 90* for 4 cylinder). This will be based off the 0* mark for TDC and the firing order... ask if you need us to elaborate.

The accuracy of the indicator that indicates crank position is one thing that is in question. So I am not sure that 0TDC as indicated on the crank pulley is accurate.

What are the other ways to find TDC of #1 on a diesel? Sorry but this is my first diesel car, I have worked on Gas engines for years now but there is a new learning curve with the diesel.

Also I guess I should have mentioned this is an 88 2.5 190D.

Thanks,
Chadd