For a 1993 Mercedes-Benz 300E, there is a problem with step for reinstalling the cam sprocket, using this guide - Pelican Mercedes-Benz Tech Article - Mercedes Benz Head Gasket Replacement - 190E, W124, W126, W201, W123 .

The actual step states for reinstalling (from Pelican Parts), "If you have not moved the cam or the crank you should be able to reinstall the cam sprocket and everything should line right up. If you have sent the head out for work, moved the cam or the crank while working on the engine things will not line up and your witness marks will be useless. You will need to set both the crank and cam at TDC for installation. If you did not move anything and everything lines up correctly, it is a good idea once the chain tensioner is re installed and everything is torqued to rotate the engine from the crank to Top Dead Center and check that everything lines up with the witness marks just to be safe."

The problem is, the crank and the cam cannot be adjusted to top dead center (TDC). The left guide rail (I believe that's the name of the part) keeps putting more tension on the timing chain as the crank and cam get closer to top dead center. This makes it impossible to put the cam sprocket back on. You can see a picture of the sprocket here - http://www.pelicanparts.com/techarticles/Mercedes-190E/25-ENGINE-Tackling_Your_Head_Gasket/images_med/pic12.jpg . The left guide rail I am referring to in that picture is directly bellow the middle yellow arrow. Does anyone have any advice to align the crank and cam with top dead center?

Are you trying to find TDC with the chain installed? Why can't you set TDC separately then install the chain?

Because the left guide rail is putting too much tension on the chain, by turning into the chain, as the everything is turned to TDC (using a wrench). The chain tensioner is not installed. I do have a question. Why is the left guide rail turning at all, without the chain tensioner installed, when adjusting things to TDC?

nr:

It may be helpful for your devoted readers if you tell us what operations you undertook that brought you to this pass. Cylinder head removed? Cam chain replacement? Rocker arm replacement? Etc., etc.

What means are you using to rotate the crankshaft, and/or the camshaft?

FYI, the rail to which you refer is on the right side of the engine. When standing in front of the car, and looking into the engine bay, it is the observer who is reversed, not the engine.

It sounds like you didn't completely removed tensioner it has an inner and outer part , it must be removed from the head which will allow you the slack to get gear/chain back on , another possibility is chain dropped down and a link is doubled up under lower gear (usually not a problem on 103 engine) back up and tell us what steps you completed before your problem started

To Nulu, that's a great suggestion. "Another possibility is chain dropped down and a link is doubled up under lower gear (usually not a problem on 103 engine) back up and tell us what steps you completed before your problem started." I think this could be the problem since the engine was tilted in the wrong direction (momentarily), as it was being adjusted (ie to and from TDC). If I remove the bottom cover to the timing chain, are there any suggestions to realign the chain?