One thing you could have done with the head off, was pour light oil or kerosine in the #1 cylinder and see how fast it flows past the rings, compared to the other cylinders. It seems that #1 cylinder fails first in most 5 cyl M-B diesels. Mine did, with chunks of something bouncing around that left deep marks in the piston and pre-chamber. Mine did have the notorious "trap oxidizer" (1985 CA). When I tore it down, ~3 pistons had chunks missing around the ring grooves, so maybe they were close to going also.

One diagnostic I have done on my gas engines is to apply air with the piston at TDC compression, and listen & feel for where it is flowing out - exhaust pipe, intake, or crankcase. I could probably do that on my M-B diesels since my HF compression test kit uses a similar quick-connect fitting.

If you do remove your engine and tear down the block, look-up my post on changing my cylinder sleeves. It was easier than most people indicate. Getting good pistons can be expensive. I left my block with new sleeves, but haven't had the top milled or the sleeves honed. Someday, when I need it.

When I did it on My Volvo Diesel I did not orient the Pistons in any special place. However, the Pistons that were at the top did not get as much MM Oil as the others did as I used the Glow Plug holes to get the MM Oil inside.
So I rotated the Engine a week later and did it again.

If you did the Piston down near Bottom Dead Center there might be a small advantage in that bore is tighter down there and the Oil would not leak by as fast. You could also put more Oil in; all though I don't think that as a good idea as it is going to leak by.
I think it is better to put in 1/4 Cup-1/12 Cup per cylinder (I used 1/4 cup per cylinder but just remembered that My Volvo is a 6 Cylinder and the Cylinder diameter is smaller and also the Pistons are flatter on top so there is less places for the Oil to pool in on top of the Piston.) and let that set and repeat that later as the Oil is going to leak down. Only the Oil that stays in the ring and groove area is going to have a chance to eat on any Carbon.

I suggest looking up some diys on the soaking.

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84 300D, 82 Volvo 244Gl Diesel

One of our Member suggested that if the Fuel Supply Pressure was on the low end that the first Element on the Fuel Injection Pump would receive more Fuel than the other cylinders.
If that is what is happening the number one cylinder would carry more of the load than the other cylinders and be worn more.

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84 300D, 82 Volvo 244Gl Diesel

I was not going to get into that until he repairs the current issue. Basically with chronic low fuel pressure on the 616 engines I believe the first cylinder is forced to carry more of the load.

So more first cylinder wear issues are reported. Especially rod bearing failures. The five cylinder 617 also can display this issue but is not as common.

The low fuel pressure issue has to be present for a very long time I suspect. This is quite possible as well.

One possible culprit is the lift pump produces less fuel pressure by design than does the five cylinder turbo models. Since it only requires a spring change to upgrade the 616 lift pump I recommend doing it. No way to absolutely prove what I believe but it does make some sense.

Just to be sure I am clear. To my knowledge we have never had a case on this site with a 616. Any additional rod bearing clearance drops compression though.

It would take those rod bearings being in an overlap situation. This would jam up an engine . To drop off compression to a hundred pounds. Or horribly worn down well into the bearing material backing.

Actually we do have regular cases of diminished compression with the 3.5 litre diesel blocks. The rods bend a little and the compression becomes so low that cylinder will not fire. Generally speaking rods on the 616 are not plagued with this issue. A much more rugged engine from a time quality was dealt with properly.

I suspect you will probably find a piston/ wall issue really. Or perhaps broken rings. I also hear the pain of sending out the head.

For future reference. I set the head upside down and introduce a little thin fluid to see how the valves are seating. Before taking a head to a machine shop and after it comes back.

Since I have limited ability I also introduce air pressure to any suspect cylinder to find out where it is going. Unfortunatly I have little time to work on mechanical systems now. I can only hope some time gets freed up as I enjoy it when I do.

The 616 is no rocket ship but I truly like the two I have. If only a couple or even just one five speed manual transmission could be obtained for them would make my day.

In case anyone missed it... the easy way to get a W201 5-speed to mate to your OM61X

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"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."