I was at the Dealership the other day talking to a customer at the Parts Dept. A Mercedes mechanic overheard me tell a customer how to set up to change out his fuel pump . I said if you turn it a few degrees past TDC you can back it up" On that sentence and the mechanic came excitedly running over and said "See, don't listen to just anybody. He's not a Mercedes employee" The customer fled and the mechanic walked away.

I saw him later as I left. I smiled and I intoduced myself and told him I am an engineer by profession and I asked him politely, "Why can't you turn an engine counterclockwise.What's the real reason" He mulled it for a minute...I asked him, "ever see an engine backfire?" He was young--some of these modern gassers never backfire...
We went through the whole scenario about the tensioning device being on the soft side of the belt-and might have to work harder, but otherwise, there is no difference except the oil pump isn't going to put out pressure.
I wouldn't run the engine ccw. But you can turn it ccw.
At least he was man enought to apologize.

You should NEVER turn the engine CCW for any reason. It can introduce slack into the chain and cause it to skip a tooth. One tooth on the OM6xx diesels is 18*, close enough to possibly cause piston-valve impact.

Even suggesting that it might be okay to turn it CCW is very bad advice.

I agree.

Turning it CCW for small increments is not going to harm anything if the chain is under tension.

You mist beware with that kind of wording. A small increment to you might be 1/4 of a rotation to somebody else.

1/4 rotation is a small increment. No harm will be done to the engine.

Diesels that are properly assembled and timed to run, do not back fire. Backfire on a gas engine usually comes from a flooded or over fueled cylinder that that fires just as you let off the starter.

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Junqueyardjim
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis



1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!

Due to backlash, final positioning most definitely should be in the normal direction of rotation.

Not a good idea on a MB V8 with their really long timing chains!

You can turn them backwards a bit, as said above about 1/4 of an inch or so.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Factory service manual for 615,616,617.91 engines page 05.4-210/3

Subject- Valve adjustment

"Do not turn crankshaft backward"

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Diesel-guy

sigghhhhhhhh now i know why..............................

this one i really loved

Really now, just how often does a modern diesel engine run in reverse?

Never seen one do it. OTH a 2 stroke engine, yes.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

I know that it was possible with the old engines. I don't know if that still applies.

They used to reverse the old Packards in the PT boats. They didn't have a reverse gear, the engines would have to be stopped and started again. That was pretty commen back then.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200