Hello everyone and a good day, too!

Now where should I begin. Fair enough. I have a 300D 2.5 Turbo, 1991, 602 engine. Yesterday I noticed when I pressed on the shock absorber which is mounted with the belt tensioner that some rattle that was present with the running engine stoped. I went to the local MB dealer and bought an entire new belt tensioner. Today I replaced the tensioner and found out I was right with my suspicion - the old tensioner's bearing was fallen apart, thus the tensioner wasn't alligned properly and also transmitted vibrations which made the engine rattle.

The other thing I noticed was that the IP leaked slightly from the top. The leak wasn't diesel but oil it appeared (dark black). I traced the source of the leak to be one part mounted on the top of the IP. The part has a ring around it which secures the part. What I did was to unscrew the ring as I thought I'd put either some kind of rubber gasket underneath it or silicone to stop the leak. I was half-way up with undoing the ring when I decided I wouldn't go for it because there wasn't enough access for me to put silicone around and I rotated the ring back - tightened it. I noticed the part on the top of the IP (around which the ring was) tilted slightly left and right, simply, it could be moved lightly. I didn't pay attention to that and simply tightened the ring around it back as it was.

Now for the intriguing part - I cranked up the engine to hear the result - I expected the engine to be quieter as a result of a new belt tensioner. It was for a moment but after I revved it up a few times it started to rattle like a harvester. A very loud banging, metal on metal. It seems to go away when I rev up but when on idle the sound is very much to be heard.

I have come to 2 reasons for that - the sound I get to hear is typical for either

1. The valve lifter (is this the correct word for it?) gave up. I know all of the lifters have been signed with age and when the engine was cold, especially in winter, they every now and then sounded this way. When the engine warmed up they went silent (more or less) though.

2. Fuel mixture (diesel) being too rich. This would indicate that the part I fiddled with on the IP had to do something with adjusting the fuel richness. To leave out this option I went back to my dealer and searched through EPC catalogues for the car to identify the part. Incredibly enough, all diagrams of IPs were of some other IP and the part did not show on them at all!

So my question is - can you identify this part for me and tell me what its purpose is? It is situated on the top side of IP, right beside the actuator to STOP lever. There comes an electric 3-line cable connected on the top of this part, wrapped in rubber. The connector to this part is secured with a black plastic ring which unlocks the connector when you turn it counterclockwise about an inch. I hope you know which one I mean, there is no other electric connector that goes to the top of IP. A part number for it would also be great if someone would know.

So it either must be a big coincidence that a lifter gave up exactly when I fiddled with that part or that very part I fiddled with is the culprit. When I unplug the connector from that part it seems it has no effect on the engine, it idles just as before, no changes noticed, the same goes for revving it up. So maybe that part has no effect on fuel whatsoever. On the other hand, there must be some purpose to it, just tell me what it is please. When I drove the car afterwards I think it was more responsive, had better acceleration. It was either my imagination or the fuel was indeed richer. But... there is no smoke, apart from normal smoke when under heavy acceleration. Now do tell what it is

Thanks a lot in advance.