timing chain slipped while replacing-help! - PeachParts Mercedes-Benz Forum

gschlump · #1 04-10-2006, 01:54 PM

So I purchased the chain replacement kit from Diesel Giant and borrowed the crimping tool with the help of the awesome MercedesShop. Removed necessary parts (I thought), undid the old chain (attatch precariously with the non-crimped temporary link), attatched the new to the old, then my helper and I attempted to reel it on. Problem was that after only a short time the engine would no longer turn. In the grunting and torquing attempts the chain jumped on the camshaft gear and slack was perhaps introduced into the chain on the exiting side. Not good!

We did not remove either the glow plugs or the fuel injection lines because it didn't seem necessary to remove the camshaft cover. We are now told it is important to remove one of these to turn the engine--so I removed both and attempted to gently turn the engine once again. Nothing.

Now I turn to the collective brillance of the list: the old chain is just about to enter where I cant get to it (with the new one attatched). I think the chain slipped so I have no idea if the camshaft, IP, and crankshaft are timed correctly. What do I do now?

A million thanks,
Gretchen
1981 240D

dkveuro · #2 04-10-2006, 02:05 PM

You need to make sure the timing is correct for the cam and crank, don't worry about the pump...just yet.

With the injectors removed you'll be able to move the engine without fighting the compression.

Roll the crank/chain back a little...then if it clears...start rolling the chain in again.

If it goes in okay...then you can pull the pump and reinstall it correctly.

We presume you removed the timing chain tensioner ...yes ?

You may have jammed up against the bolt on the pump drive sprocket that protrudes into the space above the chain/sprocket for the pump....you'll see it on the right side half way down at 3 o'clock on the sprocket bulge...looks like a drain plug.

"You have now been assimilated...your will is to do the bidding of the collective "

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Stevo · #3 04-10-2006, 02:48 PM

Its possable the engine wont turn because the valves are hitting the top of the pistons if the chain jumped more than one tooth. I would back the chain up one tooth and see if that lets it turn. I think it will turn if its off one tooth, which means when you get the chain rolled in you can check the cam and crank marks and sort that out. Then you will have to pull the IP and re install it but its not a big deal on a 240. Then it will need to be timed but like dkveuro said you can worry about that later.

Something like that happened to me the first time I did a chain on my daughters 240.

gschlump · #4 04-11-2006, 05:03 PM

Yes I removed the tensioner (and will replace with new). I attempted to turn the engine back and it went slightly, but did not help the forward turning. The injector lines are out. Should I back out that bolt on the IP side that may be obstructing the line, or what other actions can I take?

Gretchen

d.delano · #5 04-11-2006, 05:17 PM

Quote:

Originally Posted by gschlump

...I attempted to turn the engine back and it went slightly, but did not help the forward turning...

OK- you should never ever EVER turn the engine by its crank bolt counterclockwise. NEVER.
Some will tell you they've done it slightly with no ill effect, but it's common knowledge that you don't ever do that. Kinks up the valvetrain from what I understand. Engine was designed to rotate in one direction only, and that direction is clockwise. This may have something to do with why you can't turn the engine properly now.

gschlump · #6 04-11-2006, 05:46 PM

I don't think the attempt even moved the engine 2mm (thank heavens). I reread the posts and will attempt to step the CHAIN backwards. It did seem just wrong to move the engine in that way.

How much can I move the engine with the chain possibly off a link or two? Basically I'm a newbie and want to know if anything I could do right now could cause major damage. I would feel much more confident experimenting if I knew. If the timing of the cam and crank are off, can I still turn the engine?

Thanks,
Gretchen

1981 240D Odometer jammed at 127xxx km

d.delano · #7 04-11-2006, 06:29 PM

Turning the engine with the cam timing off would be like if the chain broke during normal operation. The pistons would hit the valves that were depressed by the now static camshaft, only not at running speed, at hand-cranking speed. Maybe you can see if you can find a cam in-between spot that will allow for none of the cam lobes to depress any of the valves, and turn your engine then, but you would have to find that spot with the knowledge of it being exactly the precise rotation you want the cam/crank in before you roll the chain in. To find out where this position is will require somebody who is knowledgeable. I'm thinking you are getting in way over your head with this. In fact, you are getting in way over my head with this. What you need is somebody to reset your cam to crank timing now, which may require special tools and professional know-how. Unless you just don't care what happens to this engine anymore I suggest you stop experimenting and get help from someone who knows.

engatwork · #8 04-11-2006, 07:08 PM

Quote:

If the timing of the cam and crank are off, can I still turn the engine?

After one tooth off, which is right at 18 degrees, it will not turn. One tooth off will allow it to turn and run. I have some used pistons that prove it

.

I just had one that was like that after I had pulled the crank to have it ground/polished and replace the brgs and seals. When initially lining up the crank I did not have the tensioner positioned correctly and the cam/crank became one tooth off (I did not break the chain during the procedure). After turning it over for a handful of times the cam was one tooth off. I repositioned the chain on the cam sprocket, pulled the ip and retimed it. Keep in mind this was all done with the engine on a stand so it was pretty simple.

dkveuro · #9 04-11-2006, 07:26 PM

You seem to have a valve piston contact.
You will need to retime the cam to the engine...try turning the cam either way....or loosen off the valve gaps ...(.EDIT.)

Unless you can gently turn the crank again while feeding in the new chain, the above any be unavoidable.
Duh...Of course....you can pop out the rockers to get clearence to turn the crank/pistons so nothing collides...brain fade here.

I've still got my head in this 603 !

,

tram · #10 04-11-2006, 07:27 PM

Did you remove the cam followers (rocker arms) before doing this? This is how we were taught and it eliminates the possibility of any "strike" damage, as well as eliminating compression issues. Once you get the chain on, you then turn it over 3 or 4 revs by hand with the tensioner in to see how things line up.

dieselbeagel · #11 04-11-2006, 09:43 PM

If u r sure u jumped a tooth, then hold up the leading side of the chain - the side going into the engine. Make sure u hold it up tight !

Use a vice grip on the camshaft and turn it clockwise one tooth. U can do this by taking the leading side of the chain and use it as a guide on how much to turn the camshaft.

Once u r done feeding the chain, check the mark on the flywheel and camshaft markers to see if u r good to go. Make sure the flywheel is correctly aligned. Otherwise use the above method to correct the camshaft marks.

Good luck

Hatterasguy · #12 04-11-2006, 11:13 PM

I don't see how you can hurt a valve or piston by slowly turning over an engine by hand. Well unless you really lean on the breaker bar or 1/2 drive that you are using to turn it over with.

I am not familer with the 616 but it probably isn't all that much different then the 603 in this respect. After you free it up as was said above, then you need to time the crank to the camshaft. The FSM should provide the procedure to do this. Once that is set and the new chain is in place then worry about the IP.

Stevo · #13 04-12-2006, 11:43 AM

Gretchen

Like I said a few posts back, this same thing happened to me. I turned the engine, by hand slow..clockwise, ....engine wont go any more, the valves are coming in contact with the top of the pistons. I bunched up the chain and, moved it one tooth on the cam sprocket. Does the engine turn now? Nope , I bunch the chain and move it 2 teeth the other way, it turned. I then got the chain rolled in and then checked the cam and crank marks to make sure. Anyway thats what worked for me. I dont think you could hurt anything by trying that.

gschlump · #14 04-17-2006, 05:43 PM

The chain is wound on and the cam and cranks are timed properly. I ended up removing the rocker arms then it was easy. My new problem, though, involves the master link sent to me by Diesel Giant--the link that goes in between the two chains will not slide on the master link. But that's something to talk with DG about...

What I would like to ask now is: upon turning the engine over by hand it moved fine for most of the cycle, then would need manual assistance for about a quarter of the cycle. Also, fuel would periodically squirt out of the fuel pump (injector lines removed), except for one, which stayed dry the whole time. This just seemed strange to me and I thought the two may be linked somehow. Don't know how it runs yet because of beforementioned link issue.

Thanks for all the help!

Gretchen
1981 240D

psfred · #15 04-17-2006, 09:25 PM

First thing I would do is check cam timing -- line the notch in the thrust washer for the cam sproket up with the bump on the front cam tower, then check the timing mark on the crank. Should be withing a degree or two of 0. If not, it will be off in increments of 12 or 13 degrees, one for each tooth the cam is off.

To fix, keep tension on the cam sproket while removing it from the cam, then lower it a bit and "walk" the chain the correct direction to get it lined up.

You will then need to check the injection timing -- remove the pressure valve holder on #1, remove the valve and spring, and re-install the pressure valve holder (the pressure valve holder is what the injection line screws onto). Attach a hose of some sort, and bend it over in a loop (no crimp, fuel must flow freely), or use the proper MB tool if you have it. Slowly rotate the engine while operating the hand pump (or attach a can) so that there is some pressure in the IP. Fuel will run out, then suddely slow to a drop a second or so -- this is the point were the plunger in the IP covers the fill slot. Crank must read 24 BTDC -- of only a bit off, loosen the three bolts that hold the IP on and rotate so that fuel flow just stops at 24 BTDC, then re-tighten.

If it's way off, you will have to remove those three bolts and pull the IP out. Line up the mark on the end of the driveshaft with the mark on the body of the pump (upper left corner looking at the drive end, I think). There is also a "missing spline" that matches the hash mark.

Re-install the pump with the crank at 24 degrees, and adjust timing to excatly 24.

Good news is that I dropped BOTH ends of the chain on the 220D while pulling a new one in (12 degrees of stretch, for heaven's sake, badly neglected car!) and the IP and cam timing were both OK when I got the ends fished back up.

Peter