603 timing chain swap- engine won't turn - PeachParts Mercedes-Benz Forum

New2MB · #1 04-05-2006, 08:19 PM

I decided to finally replace my timing chain, the engine was running ok but the tensioner was all the way in and I'm sure it's the original chain. Prior to this I took off the vacuum pump and got a new one but did not install it yet. I also replaced the cam gear and upper chain guide.

So I started to turn the crankshaft clockwise but it only moved about 45 degrees before it stopped. It feels like a hard stop, not a compression stroke. I put a bit of pressure on it but it seems like any more pushing and I'm going to break something.

Does anyone have any idea what I did that caused this? Do I need install the vac pump?

I looked inside the spot where the vac pump goes and I can still see the chain wrapped around the gear, nothing seems out of place.

This is on my 87 300SDL.

Hatterasguy · #2 04-05-2006, 10:04 PM

Wait a sec let me understand:
You broke the original chain, and connected the new chain to it via the old link? You made sure the connection was secure using the little center plate for the links to really hold them together well? You also tie wrapped the old chain to the cam sprocket and made sure not to lose tension on the chain. (You have to back the tensioner out of course but you need to keep the chain tight against the sprockets!)

So as you are feeding in the new chain and turning the engine over by the crank bolt the engine jammed?

It sounds like your connection to the old chain may have let go. Can you back it up a bit and see if it will move forward again?

I hate to say it but you may be taking the front timing cover off soon!

I just did the chain in my car two weeks ago so the procedure is pretty fresh in my mind.

Pete Burton · #3 04-05-2006, 11:37 PM

or did you loosen and remove the old chain and trying to move crank without cam? If so, that's the problem because the valves will hit the pistons if they're not timed on that engine (I think)

New2MB · #4 04-06-2006, 10:12 AM

Quote:

Originally Posted by Hatterasguy

Wait a sec let me understand:
You broke the original chain, and connected the new chain to it via the old link? You made sure the connection was secure using the little center plate for the links to really hold them together well? You also tie wrapped the old chain to the cam sprocket and made sure not to lose tension on the chain. (You have to back the tensioner out of course but you need to keep the chain tight against the sprockets!)

So as you are feeding in the new chain and turning the engine over by the crank bolt the engine jammed?

It sounds like your connection to the old chain may have let go. Can you back it up a bit and see if it will move forward again?

I hate to say it but you may be taking the front timing cover off soon!

I just did the chain in my car two weeks ago so the procedure is pretty fresh in my mind.

Actually, the crazy part is that I never even got the job started, I just turned the engine over. The old chain is still installed, I haven't even attempted to remove it.

However, after sleeping on it, I realized that when I replaced the cam gear a few weeks ago I probably didn't get the timing set right. I'm guessing that somewhere I have a valve hitting a piston.

I'm assuming that's possible on this engine but I don't know for sure.

So I'm going to remove the cam to release the valves and then see if it turns over. If it does, then I think I just need to get my valve timing set right. I sure am glad I didn't lean into it real hard.

New2MB · #5 04-06-2006, 10:13 AM

Quote:

Originally Posted by Pete Burton

or did you loosen and remove the old chain and trying to move crank without cam? If so, that's the problem because the valves will hit the pistons if they're not timed on that engine (I think)

I think you got it Pete, I changed out the cam gear and I must not have put it back together timed correctly.

Hatterasguy · #6 04-06-2006, 01:36 PM

Well yeah if the timing is out I bet you have a valve hitting a piston. 603's are interference engines.

With the valve cover off you can check the cam to crankshaft timing. The FSM provides the procedure. But if my memory serves me you turn the crank around until it is at 0 degrees and their is a mark on the cam that should line up at that point with a mark on one of the cam bearings.

New2MB · #7 04-06-2006, 09:53 PM

I'm officially a dumbass. I removed the cam gear and tried turning it over and I STILL hit a hard stop! I started thinking that I must have really screwed something up. Then I sat around just looking at it and what do you know, it was much easier than I thought. The assembly that holds the two front motor struts (or whatever those are) had rotated so that when the little stud on the crank pulley came around it would hit and get stuck. So I just rotated the stupid thing out of the way of the crank pulley and voila! Moral of the story: don't be a dumbass.

hughet · #8 04-07-2006, 11:54 AM

You are probably one or two notches off on the sprocket

If you remove the camshaft, be sure to remove the cam bearings in sequence or you may damage the cam. Remove 1, 5 and 6 completely and then remove 2, 3, 4 and 7 one turn at a time.

You may not have to remove the cam so try this first. You are in a tricky situation. You want to get the cam and crank timed right without having to remove and reinstall the injection pump. Did you change the cam sprocket with the motor at TDC? If so, you have turned the crank until a piston hit a valve and can probably go backwards (CCW) 45 degrees or so back to where you were while keeping tension on the cam until the damper is at TDC. I know that going backwards is a no no but it is probably OK if you turn at the crank and the cam bolt at the same time so you keep the chain tight. Then remove the sprocket and reinstall it so that the cam is at the TDC mark along with the crank with a tight chain. You can take the vacuum pump and basket out (you are going to change it anyway) and that will help you determine that the chain is tight while you are turning backwards.

If you didn't change the cam at TDC you will have to remove the cam and turn the motor to TDC and then reinstall the cam. Pay particular attention to the position of the cam remembering that the cam turns once for every two turns of the crank. It is possible to get the injection pump 180 degrees out with the cam and crankshaft aligned!

After you have done all this, turn the motor a few times CW so that you are satisfied that cam and crankshaft are aligned.

Once you have done all that you can now change out your chain. This time start at TDC and follow the directions carefully.

Your worst case scenereo is that you get it all together and the motor won't run because the injection pump is 180 degrees out. If that happens, you will have to either remove the cam again and turn the motor over 360 degrees to TDC or remove and reinstall the injection pump. Either way this is a good time to check your injection pump timing.

Good luck!