617.912 Timing Question

[savagetom]

I've got a new 1984 300D Euro version. Adjusted the valves the other day for the first time. When I finished I lined up the cam TDC mark on the bearing support with the notch in the cam shaft. When I checked the chain stretch this is what I saw.

It looks to me like the cam must be off a tooth. I'm assuming the little triangle shape piece is the timing pointer. Is this correct?

Is it possible for the balancer to have rotated out of position? It doesn't look like from the diagrams in the manual.

I know the car has had some head work in the past by the first owner. I'm the third so details are sketchy. I guess it is possible that it was assembled incorrectly.

Amazingly it runs pretty well. Starts perfectly and seems to have good power although I don't have a good frame of reference here. I haven't driven other non turbo models.

I don't want to fix something that isn't broken so I thought I should check in here first.

Thoughts?

[engatwork]

Something does not look right with the pointer. I will have to look at mine tomorrow and see if I can tell what looks out of place. Are you sure you were on tdc on the #1 piston. If it starts/runs good I think I would leave it along.
You should get some simple green, spray it all down in the area you took the pic at and then wash it off at a car wash. There is nothing you can hurt in that area with the hi pressure wash.

[leathermang]

Remember not to get ANY water on the injection pump when it is warm . The tolerances inside it are VERY CLOSE and you can mess it up otherwise...

[autozen]

If you lined up the marks carefully, it looks like a lot of chain stretch. You are not off a tooth, because if you were, the marks would be off 18 degrees. If it were me I'd fix something that isn't broke, because if you wait long enough it will be. If you wait til it breaks, you can take some comfort in knowing that it really is broke, but it will be a lot more expensive. Interesting little known fact is that the timing chain in the 240D, 300 non turbo, and the 300 turbo is the same chain.

Peter

[engatwork]

If it were chain stretch causing this then the crank indication would be past zero when the cam mark is lined up. This one looks like the crank mark is ahead of 0 when the cam mark is lined up. I'm still wondering if #1 is on tdc?

[savagetom]

Thnaks for the feedback, guys.

Jim, I agree with you on the picture indicating that the crank is behind the cam not ahead of. I read it as about 3 degrees of stretch and being off 1 tooth or 18 deg for a net reading of 15 deg.

As for the cam being lined up - I'm pretty sure I did this correctly. I've used the procedure on my son's 1982 300d Turbo saw reading of 3-4 deg ahead of the cam. The big difference is that on his car there is an obvious sharp point sticking out from the block to use as a pointer. It looks to be in about the same place as the triangle on my car, though. Once you know where to look for the cam TDC notch and the mark on the bearing holder, it is pretty hard to mess up.

Does anyone have any experience with the cam being off a tooth. Is it feasible for the car to be running fairly well?

[engatwork]

I ran the last engine in my 300D with one tooth off after I screwed up removing/replacing the cylinder head. It ran alright one on the road but shook like crazy at idle. I still have the old pistons, they have little exhaust valve indentations in the tops of them that I suspect could be machined out without a lot of trouble. I've been thinking about having the cam set one tooth early like yours and feel that it will run like that but I don't think it would be making the type of power that it should be capable of when timed properly. I'm also thinking that ever who got it off probably just adjusted the ip to get it to run "good" but this is only speculation. It is easy enough to advance the cam sprocket/chain relationship one tooth and then see how it runs. Will be interesting to see if you have to make an ip adjustment.

[autozen]

Jim,

You are absolutely correct. I blew it on this one. I must have had my head up my you know what thinking about other things. The 18 gegrees per tooth still stands. I've done valve timing many times making the measurement with a dial indicator and then using the proper offset key. The only way to be sure to know what is going on with this car is to take the measurement with a dial indicator using MBs SOP and see what's what. Thank's for catching my screw up, Jim.

Peter

[samiam4]

I've had experience here-

Yes, it's possible that you've got a harmonic balancer problem, an aftermarket timing gear etc... One tooth off and they should not turn-over(18 degrees).

You need figure it out. How does the car run compare to the other 300d??? If the timing is truely off-you'd know it in performance.


Michael

[engatwork]

I must have had my head up my you know what thinking about other things.

We all have days like that.

[savagetom]

I got the car fixed today! Here
s what I did.

I checked the crank positon indicator by removing the no 1 cylinder glow plug and inserting a clear tube filled with oil. As I rotated the engine from 15 BTC the oil level went up and then dropped after passing the zero mark on the balancer. This told me that the TDC mark on the crank was correct.

I then proceeded to pull the cam sprocket and rotate it back one tooth. This is a pretty staight forward job and is generally described in the section of the manual on replacing the cam shaft. I didn't have a pin hammer but had no trouble fashioning a puller from a 8x40 mm bolt from Lowe's along with a nut, a few washers and a socket. I used a rawhide hammer to tap the sprocket off the shaft.

I've got to tell you that you need at least 3 hands to lift the chain off the sprocket and rotate the sprocket one tooth. The chain wraps around more than 180 degrees of the sprocket and its hard to get all the teeth disenganged so that you can rotate the sprocket. It is easy to get confused on how much you have moved it. I should have marked the sprocket and chain with a dab of paint or whiteout or something. It took a couple of tries but my son and I were able to get it lined up.

Getting the timing correct has made a HUGE difference. The biggest difference is sound and noise level. At idle the engine now sounds more diesel like and at speed the car is much quieter. There was a siginficant noise level in the car coming from the right hand side of the transmission tunnel when engine rpms were elevated. I assumed this was due to less insulation in the Euro version. I now believe this was due to the the valves opening early during the combustion stroke and letting some of the explosion into the exhaust system. Anyway, it is much quieter now.

The car also has noticably more power. I didn't do a zero to 60 check before the change, but I can now power right up hills I would have bogged down and downsifted on before.

Bottom line, the car runs better and I feel like I accomplished something this Saturday afternoon.

[leathermang]

" its hard to get all the teeth disenganged so that you can rotate the sprocket. "
I think some people fashion a holder out of something like a coffee can..

[P.E.Haiges]

savagetom,

Great idea of the oil tube to find TDC. I would never have thought of that.

I'm surprised that the pistons didn't hit the valves with the cam timing off one tooth.

Have you figured out how the cam became mistimed? Could it be that you need a new chain tensioner?

P E H

[engatwork]

quote by PEH

I'm surprised that the pistons didn't hit the valves with the cam timing off one tooth.

I suspect that if the spkt had been one tooth off the other way then he would be running modified pistons (I've got a set in the garage if anyone is interested) but you won't know until you pull the head or remove the pre-chamber and use a borescope to inspect the cylinder/piston.

[psfred]

One tooth early shouldn't be a problem. One tooth late and the valves hit the pistons. Gently, I suppose, as these things go, but contact.

Funny how much better a diesel runs with proper timing....

Peter