OM-615, to woodruff key or replace timing chain?
 

So, I've moved back to New Mexico and "Trudy," my 1972 220D needs some serious refreshing. I know the timing chain is stretched 5-6 degrees just from using the timing mark on the camshaft and the mark on the crankshaft balancer. I'm hoping that 5deg is chain alone. If it already has a woodruff key installed, then we're talking serious stretch. The car runs great though so I'm thinking it's just the original chain.
Anyway, like the thread title says, should I woodruff key the gear and refresh a few things while I'm in there or should I just roll in a new timing chain from the top?
The former is way cheaper but takes marginally more work.
The latter is the better, longer term solution but way more expensive.

The car still has great compression on all four cylinders. Still has good pickup, even at 7000+ feet altitude (I've adjusted the IP and linkage to compensate for the lower air density here.) Still needs the IP to be timed better to the engine. I know my chain stretch and black smoke tells me that.

Opinions?

Thanks all.
Phil Forrest

Do the best that you can afford. You clearly know which is the better solution. And only you can decide if you can afford it.

Hey Phil, I'm not far from you in ABQ. North 14, right? We should meet up sometime. I too like W115 diesels.

As for deciding to replace the chain or go with an offset key, I just went through all of this myself on the '74. I decided to go with an offset key.

I started by measuring the cam timing in relation to the crank following the "2mm #1 intake valve down" method. I found the cam to be behind the crank by about 3.5 degrees from the specified range, at the crank (1.75 degrees at the cam).

I read into it and came to the spot you are now - chain or offset key? More information and thought was needed.

One thing I did was to check for an offset key being in there to begin with. I was able to do so by loosening the cam gear bolt part way and pulling the gear forward enough to have a look at the woodruff key. I used the bolt to stop the gear from coming all the way off, to provide just enough of a slot to shine some light on part of the key. I was able to do it without pulling the exposed slide rail. I found that my engine did not have an offset key.

Something I read about was damaged teeth on the timing related sprockets, and the need to replace the cam, crank, and intermediate sprockets, and maybe the injection timing device too. The damage is caused by the chain rollers contacting the teeth in the wrong way, from them wearing on the pins that center them. So I took a close look at teeth on the cam, the intermediate wheel, and on the crank sprockets. After cleaning the oil off in places and using magnification I could see a wear pattern down in the space between the teeth, but I could still machine marks on the fronts and backs of the tooth tips. Nothing indicated to me that an advanced wear patter had set in.

With that information I decided to go with the offset key, one that advances the cam 2 degrees (4 degrees at the crank). In the process of doing that I dropped and lost the offset key! There's a thread devoted to that recently updated chapter . . .

Now, If I had found an offset key in there to begin with I'd have wanted to install a new chain. But in the '74's case I figured I could go for a while on the offset key, since the "stretch" was not so bad with a straight key installed.

And something funny I discovered during the hunt for the lost woodruff key was that the engine had a new chain installed at some point anyway, albeit with unknown hours use as of now.

Sum: Do the 2mm intake test to get a firm number on how far behind the cam is. See if it already has an offset key. Check for wear on other components. Make decision.

I've got the dial indicator for doing the 2mm test. I'd help roll a new chain in if you decide to go that route. I'll send my contact information via PM.

Where's Stretch with all his links? :)

Just want to chime in here to say I'm in the same boat as Phil.

I can't offer any guidance but I would be happy to send an extra injection line if you would like to make a "drip tube tool". PM me with your address.

Also, thanks Gregory for the info.

I have a new chain on order for my OM617. As a race engine, it's cheap insurance as I have NO clue about the state/age of the existing chain. Besides, I want to advance the cam a bit for performance reasons - the guys in the Diesel Performance section say it's a power-adder and I need all I can get. So 2* and a 5* key are also coming.

Really, I just wanted to say that this thread is what makes this forum worthwhile! I love that the OP got helpful support without a lot of crap!

Yea, US!!!!

Dan

Re racing, I would think retarding the valve timing would give more power at high rpm, since that is true in gasoline engines, and it is the same issue of getting max air charge into the cylinder. Gas engine "timing sets" often have 3 or 7 keyways so one can pick an advance or retard from the "straight up" design. Advance gives better low rpm performance (torque) and mileage. Drag racers go w/ the retarded settings. They don't care about low rpm because they rev the engines at the starting line and release the brake, or slam the tranny in (sometimes explodes). I had a friend who drag raced a Pinto and would retard the timing (rubber belt) one tooth before racing.

Re an offset Woodruff key, I see no issue using one as long as the chain isn't so worn that the teeth aren't meshing correctly. If you ever fooled with bicycles, you know you need a new chain when it only contacts the first teeth and is slack behind. Too worn and the chain starts skipping on the front sprocket. Otherwise, there is already plenty of slack in the timing chain, so as long as the tensioner can keep it tight on the return side, there should be no problem.

I am fooling with this currently, and trying to get a good measurement with my dial indicator. Last time I checked my 1984, it had 2 deg crank retard, which is the factory 10,000 mi wear-in spec, but I recall using the marks to measure that (inexact). I replaced my tensioner chain because the original was riding cocked (contact circles ~1/2 off) and the rubber liner appeared hard & cracked when I removed it.

Right Bill - I misspoke, thinking about advancing the IP timing. Silly me!

Dan

UPDATE!
 

Ok folks, so gmog220d (Greg) helped me out a ton the other day. We got a few things sussed out: oil change, valve adjustment, checking timing with the 2mm method, pulling out my cam gear to see the offset key and were finally left with the question of what is a #18 camshaft? More specifically, we couldn't find the cam timing specs for the #18 camshaft, which is what my engine has on it. From the tag on the block, it looks like it is a Mercedes-Benz rebuild.

Things I thought I knew before working at Greg's shop:
-The timing chain was stretched about 5 degrees using the camshaft notch/tower notch against the crank.
-The IP definitely needs timing.

After the work:
-I have a camshaft with 18 stamped in the back.
-18 is not listed for cam timing specs.
-Against the 2mm valve test, my crankshaft balancer reads 16~17 degrees.
-Cam gear wear is very minimal. Teeth look good. Chain looks good.
-I have what we think is a 2deg offset key installed right now.
-My IP was missing the overflow banjo bolt/drain tube.
-I really should replace my front main seal...

Now, do any of you folks with the super secret Mercedes knowledge have the timing specs on that #18 camshaft?

Thanks all!

Phil Forrest

The W123 FSM has a bit of information about the OM615 in the non turbo section

http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/05-215.pdf

There is a 08 cam specified for the OM617 (non turbo) but I wouldn't feel safe using those specifications just yet.

My (non turbo) OM617 had a non listed code (code 11 if I remember correctly) which also made me wonder about woodruff keys...

...someone (I think it might have been JT20 - what ever happened to him?) looked up the data for me in EPC and there was more information about my cam code. In my case it turned out to be the same as code 08 and was specified in EPC as such.

(so after all that information)

Check in EPC - there might be some information in there.


I personally would just replace the chain.

I did a little bit of measuring based research on these woodruff keys and determined that their supposed correction values are a bit off. (I can link to this if you're interested)

Glad to see this posted Phil.

Cam #18 was a surprise to me. I've done the 2mm test on a few cars and always found the cam code on the chart. I'm interested to see how this one shakes out.

G

Bump.

Phil Forrest

Hey Phil, Looks like it's time to give Benz a call about that cam code.

My W115 71 220D where the engine is actually a 1973 220D has a camshaft # that was not listed in the manual too. It might have been a #18 as well. I was trying to make sure it has the correct camshaft for the valve rocker arms and nuts (soft vs hardened), but never was able to figure it out.

On the chain situation, when I had the engine apart, I closely inspected my chain and saw 2 tiny metal shavings embedded in the chain links and preventing the chain from swiveling the way it should in two spots, so I had to replace it. If it hadn't been damaged, I would have reused it with an offset key (about 6 deg. stretch).
Against everyone's recommendation, I decided to use the beck/arnley chain. The reasons (not necessary in order of importance):
1. It is a continuous chain and doesn't have to be crimped (obviously it can only be installed with the crankshaft and all guides out of the block).
2. It is made in Japan.
3. It costs $45 shipped.

The IWIS chain may be better, but it costs $120, the crimp tool is very expensive and there is the chance that you might not crimp it correctly.

That is why I would vote for using an offset key unless you are doing a full rebuild, but that's just me :)

Now a question for you - You said "I've adjusted the IP and linkage to compensate for the lower air density here."
can you elaborate on that?
I am in Salt Lake City (4400 feet altitude) and I get gray smoke when first taking off in 1st and halfway trough second, and through 3rd and 4th I see some black smoke when accelerating. My diaphragm spring had 2 thick and 1 thin shim, I removed the 2 thick shims and the smoke seems much less - I assume that the same amount of vacuum will now be able to pull the rod a little more toward less fuel. What else is there to be adjusted? And what about the ip linkage? Maybe the tickler shaft engagement - it is half ball length right now (per FSM), maybe increase it to full ball's length so that at idle and low throttle, the tickler is slightly more pulled back and applies less fuel?

X2 this is an EPC / WIS look up problem now

Called the Albuquerque, NM Mercedes dealership and talked with parts for a minute who knew exactly what i needed and transferred me to the service department. The parts guy is great but he just didn't have the service system access to find the timing for that camshaft. So, this was formerly the most helpful Mercedes dealership for odd questions I had on my old diesels. I've inquired a bunch of times about my old 1979 300D as well as my current 220D. This last call to the service department was unacceptable. After explaining my issue in detail, the service rep said, "You're free to bring it in for us to check it out and we'll correct your timing.You probably need to upgrade to a double row chain and need all the other parts in there replaced" I replied, "I have a double row chain and I'm going to do the work myself, I just want to know how the camshaft is timed since this code is not in the FSM." He said, "Well, there are forms online for that." And I promptly hung up on him.

I'll see if one of my contacts in north Jersey can help me with that code.

Now to the adjustment of the IP in tedd's question.

tedd, I removed one of the thick spacers under the diaphragm spring then have been tweaking the linkage to get the air/fuel proportion correct. I think, as the fuel impulse is a set amount per-injection, the throttle body linkage has to be adjusted separately. This is the one that crossed over the valve cover. I lengthened it this morning by one full turn on each end and she's smoking a lot less. There was some gray smoke but now it's only black after the car is warmed up. As the engine and IP are set nominally for sea-level, the lower air pressure at higher altitude will result in slight air starvation, even if the linkage is adjusted proportionally because of the log change in oxygen with altitude. Really, I need the engine and IP to be timed properly before I could get this mixture correct.

Thanks all for the help.

Phil Forrest

Boy, I knew the service guys at the ABQ dealer were "special", but not that special! Thanks for your support?

All the parts folks I've dealt with are helpful, Pedro especially. My only brush with the service department was the windshield seal I had them replace in a W123 300CD. They butchered the trim! And and I spoke with the "tech" before having them do the work, to make sure they knew how to deal with the pull seal and trim, and was assured it would be done properly . . . . .

I've got a fuel line cut and bent for a dripper. Lemme know if you want to come down to ABQ for that job, Phil.

Not sure if this timing specs from the Tech data manual helps. It shows a "13" camshaft for the 115.954 engine. Is it possible the "13" was misread as an "18"?

http://i31.photobucket.com/albums/c3...715_160118.jpg

Prompted by funola's contribution I had a quick look in the German language version of the W123 FSM and found the answer

http://www.peachparts.com/shopforum/...1&d=1436995006

http://www.peachparts.com/shopforum/...1&d=1436995006

Good on you Stretch!

Better late than never I suppose (should have checked earlier and saved parts guy encounter from happening)

Thanks Stretch! Now we're in business.

Pretty sure that we saw an "18" in there, funola. Looks like code "13" has the same specs, though.

Greg, thnaks for telling me the answer was in my thread, today.
I haven't checked this thread in over a month as Bethanne and I have been moving then moving then moving again (landlord, et al difficulties.)
Anyway, back in July on the 15th we were in an area withzero cell reception and hadn't gotten our internet set up so I just didn't see the reply.
Anyway, thanks Stretch and funola!
I've decided since I'm pretty broke, just moved into a new place, saving up for a second set of wheels for some snow tires, saqving up for snow tires and having to get my main camera shutter replaced, I'm going to take the risk of sticking in an offset key and praying I get at least through the winter. The chain wasn't badly worn, the gear teeth looked good, so I should be ok. I also figure if something catastrophic is going to happen, it's going to happen. Ouch. Yes, the new chain is a bit of extra insurance but it's 10X the price of a key and quite a bit more work.
We'll get the key in there, time the IP then I'll get that linkage readjusted for altitude.

Then I'm going to attempt to use this car as my winter vehicle up in the northern New Mexico mountains. It's al we've got and it's all we can afford. She's made it so far through some really bad winters all across the country, I think she can handle it.

Thanks all!
Phil Forrest

If your 2mm lift tests consistently read 16 to 17 degrees then I wouldn't bother with the offset key.

For the #18 camshaft that's the expected wear after 20,000km - as far as the elongation is concerned "that's a pretty new chain".

Furthermore - according to my boredom a few winters back - when I measured the camshaft profile in my OM617 and other daft things - I reckon the lower valve offset keys don't adjust for what they are meant to adjust!

See =>

http://www.peachparts.com/shopforum/2836492-post25.html

(if you want)

Phil, no sweat on the heads up. Sorry I couldn't check it for you right then as we were in the middle of packing boxes and moving stuff into storage in preparation for our upcoming move.

I really didn't take a close look at the data or give this any thought after Stretch posted his copy of the chart. Indeed, it appears that 16 ~ 17 degrees at the crank on the 2mm test would be just in spec, as Stretch has pointed out. The 2 degree (at cam) key would improve your cam timing a bit, and wouldn't be a total waste of time, perhaps. But also can see how leaving it as-is would be fine.

Why are the specified ranges so much larger for this group of cams?

Stretch, I am curious to hear more about how the smaller offset keys don't actually adjust how we want them to. When I went through this on the '74 the cam timing was behind the outer spec by about 3.5 degrees at the crank. I installed the 2 degree (at cam) key and it brought cam timing up about 4 degrees (at crank), to just within the specified range.

That is wrong... you can not compare gas engines to our diesels on some factors... and this is one of the most important.. it is the reason our engines are so efficient ... gas engine users change the valve overlap when they want more power... wasting fuel in exchange for more complete exchanging of the gas air in the cylinder during the compression stroke. By definition our engines relationships are determined by the IP rpm curve built into the IP.
And OTHERS.... NOTE the threads in my signature with regard to timing.

I'm not sure but I assume that's because of the influence of the development of the OM617 turbo. The second generation non turbo OM617s were upgraded with "some of the lessons learned" from the turbo development - I guess the cam profiles were from that era.

Finally discussion!

I've been wondering about these offset keys for years. As explained above I did some measurements for myself a few years back (when I was really bored). The FSM gives the offset value in terms of mm and degrees. According to my measurements I got the impression that the smallest key did a better job at adjusting 6 degrees instead of four (at the camshaft)...

...I didn't get so bored as to go and buy an offset key - measure the offset in mm and then check the measurements and calculations I had made...

...you see I'm only about 80% geek! Should have gone the extra 20% just to see.

I must say your report does give me a little bit more confidence in these keys. I wonder how many people re-perform the 2mm lift test after fitting an offset key though - that would seem like a pretty good working practice! (Especially as I've heard of people putting them in the wrong way round)

Interesting to look into it now that I'm awake and see that the chain is still within spec, though just on the edge.
Although I already have an offset key with a very small offset. Maybe 2 degrees?
So, no offset key to take up that stretch just do the IP timing? Although it's on the edge of being within spec, wouldn't accounting for a few more degrees of stretch make some sense?

Again, thanks to all for your advice!
Phil Forrest

Phil, I've got a 4 degree (at cam) key that we could compare yours to to get an idea of what its offset is.

Stretch, yes I did check the cam timing again via 2mm test after installing the offset key. I also noted observations of the crank in relation the cam tower marks before and after the key was installed. All my measurements/observations indicated that I did indeed get maybe a hair on the plus side of 4 degrees at the crank from the 2 degree (at cam) offset key (~ 17 degrees went to ~ 13 degrees 2mm test, and 4 ~ 5 degrees by the cam tower marks method went to ~ 0). So my cam timing actually ended up slightly in the "new" chain range. Should be good for a while yet, and next time I'll just replace the chain. This particular engine is a 616.916 with cam 06. And my notes indicate I used 13.5 degrees as the benchmark.

I find it good practice to take measurements at least twice to ensure consistent readings. If the two measurements are not consistent I'll repeat until I get a feel for the average.