Changed head gasket, runs rough now! - PeachParts Mercedes-Benz Forum

Sugi · #1 06-03-2009, 03:09 PM

1981 300D (non-turbo). This car ran great until the head gasket went out. I let her sit a few months and just got around to slapping a new gasket in. The torque sequence for the head really makes you have to concentrate! Anyhow, it took a while for me to start her up. Lots of bleeding the lines, cursing, and (don't give me grief) a little tiny squirt of ether. It now starts and runs but sounds like a big ol' Cummins truck engine. It won't idle but will run steady if I keep my foot on the pedal a little. I cracked each injector line while it was running (brick on the pedal) and the engine changed tune with all 5 indicating that they all are firing. It's black smoke out the tailpipe- not "tractor pull black" but not where it used to be which was almost no smoke ever. Anyone have any ideas? It seems like it would not run if I got the cam that far off, right?- as far as I can tell, the cam and cam tower marks line up when the engine is at TDC. I adjusted the valves, filters new. Perhaps the I.P.? Any thoughts appreciated...

Sugi
1981 300D (Hermann)

#2 06-03-2009, 03:17 PM

First thing to do is check the timing on it. And then double check the timing. I am sure a haynes manual or the factory bible will have what the timing is supposed to be. Or it might be you jumped a tooth on your gears for the timing chain....maybe. Hope this helps.

JonL · #3 06-03-2009, 05:36 PM

It sure sounds like you have skipped a tooth on either the cam or the IP or both. Probably the IP, since a tooth off on the cam should be pretty obvious with the timing marks. You should perform the factory recommended procedures for checking timing of both the cam and the IP. You should also (perhaps first since it is easier) double check that you adjusted the valve clearances properly. Good luck!

barry123400 · #4 06-03-2009, 11:03 PM

Besides the smoke is power way way down? First check the injection pump timing. Usually you have to remove the camshaft to land up totally wrong on base timing.

You did line up the balancer and cam marks before you removed the chain and lifted the head? Just checking. As long as you did not move the cam between the time you removed the chain and put it back on the base timing should be still good. The cam and balancer marks mean basically nothing if you moved the cam gear quite a bit.

Sugi · #5 06-03-2009, 11:46 PM

OK- when I was changing the head- I had the chain wired up so it wouldn't fall down. Head was off, pulling exhaust manifolds- forgot that I had put the battery cable back on the positive side! Manifold somehow grounded out the started and it went rrr-rrr just a little before I grabbed the manifold and made it stop. Honestly I don't think it moved at all or if it did, only 1/10 of crank rotation. The wire held tight and the chain never went completely slack. Now here's the weird part- you have to pull the cam, rockers and such to get the head off. When I went to put it back together, I had to really wedge the chain up (sprocket was on the chain) to get the hole in the sprocket to match up to the hole in the cam. The chain made a kind of ratcheting sound like I was taking up slack from the tensioner. I did get it back on. The pointer on the balancer was at 0 and the marks on the cam and tower were perfectly lined up. It took a while to fire but it did and it ran rough and sounded very truck like- never heard a MB sound like that- it was not injector nailing, just loud. I did not try to drive it but it "felt" weak when I revved it (you can sorta tell from the torque reaction I think, maybe not). I'm gonna check the IP timing tomorrow(if it doesn't rain) and see if it got off somehow and also recheck the cam timing just to make sure. Thanks for all the suggestions and keep 'em coming.

Sugi · #6 06-04-2009, 07:51 AM

I went out and painted the balancer with silver paint this morning (just a light dusting). It turns out that I was looking at the wrong number! The crank is at 20 BTDC when the cam is lined up. I can't believe it even ran! Now I know my problem, I just have to figure out how to scoot the chain over to the right place...

Sugi · #7 06-04-2009, 08:26 AM

It was easy to pop the cam gear off and rotate the chain over on tooth. I'll post pictures and a running report later, gotta beat the rain!

nhdoc · #8 06-04-2009, 09:41 AM

Quote:

Originally Posted by Sugi

I went out and painted the balancer with silver paint this morning (just a light dusting). It turns out that I was looking at the wrong number! The crank is at 20 BTDC when the cam is lined up. I can't believe it even ran! Now I know my problem, I just have to figure out how to scoot the chain over to the right place...

doubly lucky if you didn't bend a valve too, those clearances are pretty tight!

JonL · #9 06-04-2009, 10:03 AM

Good luck... I'd guess your IP timing might also be off, hopefully you lucked out. Also hopefully you lucked out regarding piston/valve clearance.

Sugi · #10 06-04-2009, 12:28 PM

I got everything back together and cranked it up. Runs and sounds better for sure but still not quite right. I did drive it down the street and it was very weak. Still won't idle at normal speed, had to use a stick between the seat and the pedal to keep it around what I estimate (no tach) at 900-1000 rpm. I let the engine run for a while and get good and warm. Hopefully this will let everything "bed in" some so I can adjust the valves (probably would be out b/c I moved the cam a little). I still have not checked the IP- I need to make or borrow one of those short overflow lines used to check start of delivery. I did run a can of diesel purge and that helped even more. Here's a picture of how far and which direction the cam was off

I painted the red paint where it was at first, then moved the chain around. It was one tooth off, just like you all said it would be. I think this got me out of the valve bender zone (barely I'm sure!)

If that does not work, here's the link http://picasaweb.google.com/lh/photo/VrYOyMdr-swYsmaCeGEc8g?feat=directlink

barry123400 · #11 06-04-2009, 05:21 PM

One tooth off will not bend a valve usually. What in my opinion you should do now is turn the engine over until the number one pump element flows fuel. Might use the welling up method as it is both good enough for your purposes and in the archives.

Then check to make sure the number one cam lobes are pointing at 10 and two oclock when that occurs. There is a possibility still that the injection pump is on the wrong stroke. I would check this first just in case.

The way the engine is running and blowing black smoke. Plus the non existant ability to idle are also typical of this senario. You would not be the first either. Power should also be down in my opinion. Apparently it is I see.

Sure it could be something else. Yet if you invited me by it probably would be the first thing we checked. It is very easy to do and gets the possibility of it either out of the way. Or locates the fault to correct.

These engines will run but not idle properly at all if the injection pump is injecting on the wrong stroke and they will smoke with that problem. Inefficiency of combustion by products cause the black smoke as well. Keep the members informed.

Sugi · #12 06-05-2009, 02:16 PM

I checked the timing this morning using the "bubble method". What I found is that the timing on the IP was advanced to over 40 degrees! I loosened all the bolts and moved the pump as far as it would go away from the engine. Interesting enough, there were deep scribe marks at that position. I could not get the pump far enough out to bring the time any closer than about 30 degrees. The slots that the studs ride in were all the way over. My battery was about dead so I'm charging it now to see it that helped. Any thoughts on what to do about the lack of room to adjust IP timing? Man, that last bolt at the end of the pump near the oil filter is a B!Tch. Any tool better than an open/boxed end gearwrench 13mm? Socket will not fit...

kerry · #13 06-05-2009, 02:43 PM

Not sure how many teeth there are on the cam gear to calculate degrees, but I'd guess you're still off a tooth.

JonL · #14 06-05-2009, 03:46 PM

Sounds like you will have to remove the IP to move it however many teeth on the spline required to get it right. I'm familiar with the process on a 602, but not on yours.

barry123400 · #15 06-05-2009, 09:52 PM

Quote:

Originally Posted by JonL

Sounds like you will have to remove the IP to move it however many teeth on the spline required to get it right. I'm familiar with the process on a 602, but not on yours.

Sounds about right. Degrees per spline where discussed somewhere awhile ago. Perhaps somone with a more retentive memory can post.

One more thought since you are now going to time the pump. Switch over to the drip method might give lesser variation or more accuracy. Hard to mistake the drip method. I suggested the bubble method just to check the stroke/pump relationship.