PeachParts Mercedes-Benz Forum - View Single Post - Why is turning the engine over counter clockwise bad?

whunter · #12 12-13-2010, 12:38 AM

Quote:

Originally Posted by okyoureabeast

This is a question coming from mere curiosity as I try to respect all of the warnings in the FSM and on this forum.

Why is turning the engine over counter clockwise very bad?

There are many factors of why it is bad.

* Tension must be fully loaded in the correct direction to determine/set base mechanical timing = backing up generates slack on the wrong side even with a new timing chain chain = you must rotate one full crankshaft revolution in the correct direction to guarantee chain loading.

* Excess load on the timing chain tension rail (banana rail), breaking the plastic guide surface.

* Defective/damaged timing chain tensioner ratchet failure = collapsing = chain slack = skipping teeth/timing loss = possible mechanical engine damage.

* Lack of lubrication.

Quote:

Originally Posted by auspumpen

If I had to guess, I'd say that the problem with counter-rotating the engine is in the injection pump. If you look at the camshafts in these inline pumps, you'll see that the cam lobes have a very steep drop-off when the plungers are unsprung, so going backwards up that ramp is possible, but potentially problematic.

Here you can see OM615 and OM606 camshafts side by side:

Thanks for the great picture.

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