Timing marks gone from my OM617 engine
 

Hey folks,

I've been busy working on my W123 1981 300D this weekend - fixing my leaking front crankshaft seal and I've just noticed that some monkey (probably a monkey anyway) has snapped off the timing marks bracket.

Do any of you experts out there reckon I'm going to have problems:-

1) Finding a replacement (new or used)
2) Fitting a replacement bracket and knowing that the position is actually going to be correct?

Any help would be greatly appreciated

(A search for OM617 timing mark gives 3 hits that don't quite answer my problem)

Answer
 

Get one from any OM617 at the pick-n-pull... :D

This is also the bracket that holds the tachometer sensor.








Have a great day..

WOW thanks panic over!

Update
 

You would not believe the hassle I have had getting hold of one of these blinking things...

Most scrap dealers over here don't know what you are talking about - and it is unobtainium at the dealer...

Anyway I've got one now - I've found some information in the FSM for setting it up correctly which I'll add at a later date.

If your Engine is still apart you should have an easy time setting the Pointer.
Ounce you are to the point where everthing is assembled but the Head is not one yet set Up a Dial Indicator over the #1 Piston and rotate it in the direction of rotation till it is just at top dead center. The Pointer that you replaced should point to Zero degrees. Which nicely is the same positon you want to install the Camshaft Gear.

I believe in the Manual to check the Pointer they have you useing the Dial Indicator going down though a Precombustion Chamber hole.
It will be much easier to do with out the head on and way easier to get the Dial Indicator mounted straight.

Indeed and then to set up the correct position for the tach sensor bracket you need to rotate the crankshaft by 20 degrees - which apparently is when #1 piston drops by 3.63mm from TDC...

This will be much easier when the head is off - otherwise you need to disconnect the valve spring from the first valve on #1 cylinder and rest it on top of the piston and measure the deflection of the valve stem to find TDC and then the 20 degree point... (according to the FSM)

Edit:-

For those of you trying to do this with the head on - make sure the piston is close to the top of the cylinder otherwise the valve will drop right in there! An easy way to check the position of the cylinder is to unscrew the glow plug and listen and feel air being pushed out of the cylinder as you rotate it (make sure you stop close to TDC when the air stops coming out - not when the air stops going in!)

Be sure to add this to the W123 Unobtainium thread that is floating around.:D

Good that you found it. That piece does not get used very often, but it is critical when you do need it.

Finally got the bits and all of my ducks lined up and look:-
 

Here are some pictures of setting up and checking the position of the TDC slide. As you can see the head is off - pistons and crank are installed - upper half of the rear crankshaft seal and the front crankshaft seal are in position.

Dial test indicator DTI is used to see when #1 piston reaches end of travel (needle stops moving and starts to head back the way it just came).

There is no adjustment on the pointer bit - just fit it in place - but you can just about see from the picture that there is a hair's breadth of a difference between the zero degree mark on the crankshaft weight and the end of the pointer. Worth remembering!http://www.peachparts.com/shopforum/...1&d=1291214391

http://www.peachparts.com/shopforum/...1&d=1291214391

And here's the bit for the tachometer senor...
 

To find the position for the tachometer sensor you need to rotate the crank clockwise by 20 degrees - this is measured with the DTI => 3.63mm downwards (according to the FSM). You then position the mount for the tachometer sensor so that the pin on the crankshaft weight is in the centre.

http://www.peachparts.com/shopforum/...1&d=1291218433

http://www.peachparts.com/shopforum/...1&d=1291218433

You don't have to do this with the head off - you can do this by resting the first valve at the front of the engine on the top of #1 piston.

Awesome work Army! Looks great.

Congrats on getting that missing piece.

Are you doing a full rebuild or just the head?

Unfortunately it turned from just a head rebuild to a full rebuild - the cylinder bores were a bit patchy. You could see where there was ring contact and where there was not... so I ended up getting a re-bore and new pistons which turned out to be cheaper than having the liners replaced here in Holland (this is partly due to high Dutch labour rates and that my engine is a non-turbo OM617 => these pistons are way cheaper than for the turbo).

A full rebuild wasn't the plan - and it has pushed the project from the summer months into the winter months which makes things a bit more interesting when you're battling with crappy weather as well... hopefully in the New Year I'll get to drive my brand new 30 year old car!