w123 300D help me figure out why it died - PeachParts Mercedes-Benz Forum

orthotomeo · #1 11-01-2006, 03:10 PM

I was gonig down the freeway at about 90KM an hour or so and all of a sudden heard a whackety whackety whackety whackety (etc. until the car stopped).

It won't start at all and it feels like theirs very little resistance. I took off the valve cover and the chain and cam look in tact. Any ideas what this could be?

I looked through the search, but couldn't get any conclusions.

MattBelliveau · #2 11-01-2006, 04:12 PM

Was the engine still running under these noise conditions? Did the engine die, then start making the noise? Did you check chain tension while you had that valve cover off? Could be a rail. Could be a rod. Give more specific info, please. Thanks!

barry123400 · #3 11-01-2006, 06:59 PM

I just guess since you state no or not much resistance when engine rolling over now that you might have jumped your chain. Set engine to mark and check position of cam mark. The no resistance or very little when turning over might be cam off but hopefully not to the extent of bent valves. About the only thing I can think of that would lower compression so much that engine spins over pretty freely. Or a lot easier than before. I hope the wackety whack sound was not the valves hitting the pistons but might have been. Make sure the cam is turning at the far end of the engine as well when checking if the cam timing seems on. Broken cam although unusual could do this as well I imagine. Again the real clue from your description is you have very little compression to slow the starter down apparently now.

Mister Byrnzoil · #4 11-01-2006, 07:05 PM

vacuum pump grenaded? altho I'm not sure how this would cause a no start condition.

barry123400 · #5 11-01-2006, 07:21 PM

Sure chain could pick up a piece of the vacuum pump and feed it through a sprocket putting the timing off. Happened reciently with a member I believe and was not cheap to rectify.

#6 11-01-2006, 07:28 PM

Quote:

Originally Posted by barry123400

Sure chain could pick up a piece of the vacuum pump and feed it through a sprocket putting the timing off. Happened reciently with a member I believe and was not cheap to rectify.

That would be me.

Fortunately, in my case the chain only moved one tooth and the valves did not make contact. The car would restart, with very low power and lots of black smoke. I ended up replacing the vacuum pump, timing chain, tensioner, rails, cam sprocket, and valve cover. Lots of debris ended up in the oil pan too.

orthotomeo · #7 11-01-2006, 07:45 PM

I expected a mess when I opened it up, but what brief look I did take didn't cause any alarm. I'll have to look into the suggestions. I've never had to set a timing chain before so I'm not sure what I'm supposed to be doing.

Sadly I have no free time to pour into the 300d. (I've got a camry whose transmission just blew the day after the mercedes broke down)

unkl300d · #8 11-01-2006, 10:20 PM

did the engine cut off or did you stop because of the noise??

Is your starter motor working???

your post is not too detailed.

hope it is a simple matter.

barry123400 · #9 11-01-2006, 10:38 PM

It never rains but pours from time to time for you as well as me it seems. If your valve cover is still off it should take no more than ten minutes to put the damper pully on zero and see if the camshaft marks line up. Simple quick conclusive test. If you do not know what the cam timing marks look like on these old diesels just look in the archives. There is no physical evidence to find if chain has jumped sometimes. Most the time problems are visable when chain has broken. Of course paying attention to that area is only really required if the starter seems able to turn the engine over much faster now than it ever did before. Otherwise it is just something to check in the natural progression of locating a problem.

orthotomeo · #10 11-02-2006, 05:39 PM

So the starter turns over easier than ever before. I'll have to do some research to find out about those timing marks. Thanks for the advice.

orthotomeo · #11 11-13-2006, 09:08 PM

So I've done the research and found out how to check the state of the cam timing. 1st Cylinder at Top Dead center and check the cam notch lines up. Is that correct?

Now when I look at this (probably tomorrow) I'm wondering how to fix the problem if this is it? Do I back out the cam tensioner and then lift the chain and adjust the cam position?

Thanks.

t walgamuth · #12 11-13-2006, 11:15 PM

when you turn the key is the engine actually turning over?

if it is not it could be a bad starter or (shudder) a broken crank. or a sheared off flywheel.

tom w

orthotomeo · #13 11-16-2006, 01:50 PM

Could someone confirm that for me to adjust the chain that I'll need to back out the tensioner.

Also, are mysteps correct? How do I check for top dead center? Can I do it by just manually cranking the engine around? if so what am I looking for. I have some ideas, but I don't want to make a mistake.

rhodes2010 · #14 11-16-2006, 03:17 PM

You can probably leave the tensioner alone. I only back mine out when replacing the chain.

For purposes of your test simply rotating the engine clockwise until the
timing mark on the crank dampner and the block line up to zero are enough.

Then you are either at TDC (Top Dead Center) for number one compression or
exhaust (exhaust at beginning of intake).
For TDC compression both lobes on the cam would be away from the valves
on the first cylinder and the bottom part would be closest to the valves.
Look on the camshaft gear, there should be a dimple/indent mark. This mark
is either lined up with the cam support , or it is 180 degrees off (at the bottom).

My guess is you did jump a link or two. That would cause the easy spinning
from no compression. This could also have resulted in bent valves (don't be alarmed - it happens), which also cause easy spinning no compression.

I cannot comment on how to check the rods, if you here any clunking during your cranking of the engine that would be my guess though.

A compression test is in order here too. You can probably borrow a guage if you do not have one.

If you search the forum for chain stretch you can find how to check the chain for being stretched, these same directions apply to figuring out if your
chain is correctly aligned.

Good luck.

orthotomeo · #15 06-26-2007, 12:13 PM

Sorry, I forgot to follow up on this. I guess it was dark when I looked at the engine last time. I took the whole valve cover off and took a look. The camshaft looked ok, but when I pulled it it ended up being broken in two places. I tugged on the chain and it came off. Looks like the timing chain was the culprit. It broke.

I now have a parts car for my new 300D. He 1980 is now in the garage. I'm sure I'll be needing the a/ccompressor etc.

Thanks for the advice btw.