Cam Timing / 2mm Lift Method

[cbjukraine]

I did a valve adjustment and checked the timing chain stretch today. I think I did everything correctly (by the FSM). I came up with 11 - 15 degrees of chain stretch, depending on which side of the balancer disc indicator you're supposed to read. I assume it's 15 degrees because the chain is not new and the appropriate value per this FSM is 11 degrees.

Can someone confirm which side of the indicator you're supposed to read? The flat side or the angled side? I hope it's the angled side, then I'm right on and there's no stretch. But I don't think this is the case because I've been noticing a bit more smoke lately.

If I've got 4 degrees of stretch, what is my next move?

By the way, this is in an 84 300D with the 617.952 (I think this is the correct suffix for my 617. I have yet to find the number anywhere on the engine.).

Thanks,
Curtis

[Brian Carlton]

Originally Posted by cbjukraine

I did a valve adjustment and checked the timing chain stretch today. I think I did everything correctly (by the FSM). I came up with 11 - 15 degrees of chain stretch, depending on which side of the balancer disc indicator you're supposed to read.

You do not have 11-15 degrees of "chain stretch". Presumably you have a reading of 15 degrees which is to be compared to the specification of 11 degrees for the 05 camshaft. This would indicate 4 degrees of elongation.

Originally Posted by cbjukraine

Can someone confirm which side of the indicator you're supposed to read? The flat side or the angled side? I hope it's the angled side, then I'm right on and there's no stretch. But I don't think this is the case because I've been noticing a bit more smoke lately.

Your hopes are dashed..........the side without the angle is the side that is read.

Originally Posted by cbjukraine

If I've got 4 degrees of stretch, what is my next move?

If you want perfection, you go to the dealer and order a Woodruff key, p/n 621 991 04 67 and install it between the cam sprocket and the camshaft............be very careful not to drop it in the abyss.............it'll wind up in China.

You should note that most of the vehicles on the forum have elongation that is in the range of yours (including my SD), and the performance is only marginally affected.

[vstech]

Originally Posted by Brian Carlton

If you want perfection, you go to the dealer and order a Woodruff key, p/n 621 991 04 67 and install it between the cam sprocket and the camshaft............be very careful not to drop it in the abyss.............it'll wind up in China.

You should note that most of the vehicles on the forum have elongation that is in the range of yours (including my SD), and the performance is only marginally affected.

... I'd think that True PERFECTION would arrive with the addition of the key, AND the injection pump timed to match the offset...

if not a new chain rolled in.

[Brian Carlton]

Originally Posted by vstech

... I'd think that True PERFECTION would arrive with the addition of the key, AND the injection pump timed to match the offset...

if not a new chain rolled in.

True, of course...........but, let's not go overboard...........we'll be into "drip timing" all over again...........

[cbjukraine]

Is the low-pressure method (drip test) of checking injection timing not a good one?

[Brian Carlton]

Originally Posted by cbjukraine

Is the low-pressure method (drip test) of checking injection timing not a good one?

The method is excellent when used by an individual who is thoroughly familiar with the procedure and the specific techniques required to achieve an accurate result.

In the hands of most others, it's nothing more than a crapshoot.

[cbjukraine]

Makes sense. The whole IP seems daunting to me.

How does the IP timing get out of adjustment? Is it only the result of an elongated timing chain? Or are there other factors at play?

[cbjukraine]

how does an otherwise properly functioning and maintained IP get out of its proper timing adjustment?

[Stretch]

Any machine needs maintenance. In any machine you have moving parts. If you have moving parts you'll have friction on the moving surfaces - that means wear. The IP essentially consists of a camshaft with plungers / pistons that go up and down on top of the cam lobes. These will wear. Eventually it might be necessary to take your pump to a shop to get it all readjusted.

From a DIY mechanic's point of view, however, it is probably realistic to expect that the plungers / pistons can get gunked up with crud - that's why people talk about using additives to clean out their injection systems or to do such things as Italian tune ups - where essentially a load of good old hard work will help clean stuff out. A good example of this is a petrol hedge trimmer / chainsaw that only gets used once a year - a bugger to start at first but use it for a while with vigor! and it will start to become a good tool again.

On these engines, however, the chain elongation often plays a greater part in the effect of performance rather than how dirty / how out of adjustment the IP is. These Bosch IPs are really good bits of kit.

[cbjukraine]

So is my assumption correct that a new timing chain would rectify both cam and IP timing issues or at least get me pretty close to spec?

To my inexperienced eye, rolling in a new timing chain seems easier than messing with taking the cam sprocket off and installing a woodruff key, not to mention messing with drip timing on the IP.

Thoughts? Advice?

Thanks.

[Brian Carlton]

Originally Posted by cbjukraine

To my inexperienced eye, rolling in a new timing chain seems easier than messing with taking the cam sprocket off and installing a woodruff key, not to mention messing with drip timing on the IP.

Thoughts? Advice?

Thanks.

Both have their dangers. You need a minimum of two people...........preferably three............with a careful procedure to prevent loss of the chain from the cam when you roll in a chain. Plenty of folks have screwed that up. You also need the crimper to attach the master link, unless you're very good with a drift.

The cam sprocket comes right off with the removal of one cap screw. The dangers are the camshaft slipping rearward and the thrust washer and/or the Woodruff key falling into the abyss.


The Woodruff key is far less costly and your chain is not elongated by all that much.............

[cbjukraine]

Just read diesel giant's pictorial for timing chain replacement. If something falls into the abyss, wouldn't it end up settling in the oil pan if you rotated the engine slowly by hand? Then you could remove the oil pan to retrieve?

Or am I over-simplifying this?

[Brian Carlton]

Originally Posted by cbjukraine

Just read diesel giant's pictorial for timing chain replacement. If something falls into the abyss, wouldn't it end up settling in the oil pan if you rotated the engine slowly by hand? Then you could remove the oil pan to retrieve?

Or am I over-simplifying this?

In theory, everything ends up in the pan.

But, if it jams in the chain on the way down................much safer to ensure that you cannot drop anything down there.

[Stretch]

Originally Posted by cbjukraine

So is my assumption correct that a new timing chain would rectify both cam and IP timing issues or at least get me pretty close to spec?

To my inexperienced eye, rolling in a new timing chain seems easier than messing with taking the cam sprocket off and installing a woodruff key, not to mention messing with drip timing on the IP.

Thoughts? Advice?

Thanks.

Sorry but I don't follow your logic. Are you trying to avoid drip timing an IP by putting in a new chain? You should really check begin of delivery after replacing the chain.

Do you have access to the factory service manual (FSM)? Chapter 05-320 is your man!

If you want to correct for chain elongation then I'd go for the offset key - although I don't think I'd bother for 4 degrees => from my calculations the MB key is a bit out at the lower degrees of elongation

OM617 (non turbo) cam profile specs, piston height specs etc

I think an offset of 0.49mm is required not 0.7mm - but anyway there's nothing you as a DIY mechanic can do about that discrepancy => you can only choose to use the key or not.

[gonzalo75]

Hello,

In the FSM for the OM601 engine, in the camsaft timing chapter, it says "corrections are not possible at the moment".
I therefore understand that no off-set woodruff keys are available for this engine.
This seems to imply that once a new chain is rolled the camshaft timing will go back to nominal specs. Is my reasoning right?

Thanks
gonzalo