Cleaned 2 sets of injectors from 2 1985 300d's as per the excellent instructions posted by Jeremy 548, "DIY injector cleaning".

The first set resulted in a dramatic improvement in starting a vehicle that runs mostly on unheated WVO, that had sat for 9 or 10 months. Runs better too, but still smokes some. One injector hole had no heat shield (unless it blew out when i tested compression, 300 p.s.i. all around, cold.)

I was surprised that the inside of those injectors were surprisingly clean for 35,000 miles on WVO and who knows how much by previous owner on diesel. But there was a lot of crud right in the needle area.

The second set was marked 300 bar, and am guessing they were Monarks, 'cuz there was a crown symbol on each injector. They weren't as clean internally as the WVO ones, coming from a car that saw little WVO use. Unfortunately one got damaged on re-assembly 'cuz the pressure pin went askew. I found a Bosch VW injector marked 350 bar, & cleaned that as per the procedure, but it leaks at the seam.

Wondering what the preferred pop pressure is for the OM 617. I have a lot of 130 bar injectors that i think came from old VW rabbits. Mostly Bosch. Would they work well enough? Should i try to find another crown symbol (Monark?) 300 bar unit?

As always, appreciate any advice on this subject.

All of My Cylinders but one have 350 psi plus cold compression. The low one is 300 psi.
That low pressure cylinder nails loud until the Engine is warm and eve then at idle is slighly louder than the Rest.
All the Injectors are in excellent shape and the open pressures are still balanced.

So you have low compression and said you claned but did not rebuild the Injectors so I think the combination of the 2 could easily cause some smoking issue.

Except for not using a Lapping Plate these instructions are the closest I have read to being similar to what a Shop would do when they rebuild the Injectors.
Vince Walden how to rebuild IDI Injectors.
http://vincewaldon.com/index.php?option=com_content&task=view&id=20&Itemid=28

Cleaning the Injectors does nothing to help the seating area where the little Needle/Pintel seats. Not only does the Spring pressure push that thing down and beat Metal to Metal millions of times little particles get caught between the seating area and just like Water errodes away the Land the Fuel Pressure actually errodes away the Steel.

What that means is once the seating area is worn out it will not hold pressure well and the spray pattern will not be good. Time for a new Nozzle.
Also 300 bar = 4,350 psi and that is too much pressure for my 84 300D Turbo Diesel. I think the 300 you are seeing means something else.

http://www.worldwidemetric.com/metcal.htm

When trouble shooting it can be a good idea to use Diesel Fuel during the trouble shooting period to rule out the possibility that the problem is being caused by the alternate Fuel.

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84 300D, 82 Volvo 244Gl Diesel

Wondering if The compression is so low at 300P.S.I. (measured cold) that i should just get rid of the car and not bother with the other issues. I had thought that compression tended to read low with the engine cold.

Also, wonder if 130 bar Bosch injectors from a VW are OK to use; they sure look similar.

Thanks

It is a guess but I am guessing it is a combination of Compression on the Low end and worn out Injectors. Not having the WVO heated also makes it harder for the Injectors to atomize the Fuel.

On the Stock Injectors for My 84 300D pop at 135 bar is on the Injector Body.
In the Manual new is 135-143 Bar. The lowest allowed service pressure on a new Nozzle is 120 bar.

A long with the above the Nozzles opening/pop pressure is not supposed to vary more than 5 bar. And most Shops will try to get it closer than that.

I have not read of anyone doing a hot Engine Compression like the Manual Calls for so I cannot say what the difference would be between hot and cold.

I am only saying that I tested My Injectors trouble shooting for the reason I was getting a nailing sound on one Cylincer and all the Injectors were good (rebuilt 26-28 thousand miles ago) and that lead me to doing the compression test and I found that the Nailing Cylinder was 300 psi.
Also I live in S CA and it is not cold here.
So I am speculating that if My one Cylinder is nailing due to the poor compression what would it be like if all of the Cylinders were at 300 psi?

Concerning the VW Injectors. If they are used Injectors the actual Pop Pressure is going to be lower then is on the Injector Body unless someone has checked and re-set them.

My Volvo Diesel has a VW Engine and VW Injectors in it. The Injector Nozzles are not the same.
The Mercedes Nozzles have tiny Passages drilled in the Needle/Pintel and at idle the Fuel is supposed to go through those passages. The Monar Nozzles and the later Mercedes Nozzles us a flat spot on the side of the Needle/Pintel for that idle Fuel.

The VW Nozzles don't have either set-up for the Idle Fuel. Bosio Nozzles are constructed similar to the VW Nozzles. Some People have said they make more noise at Idle so I suspect the same would happen if you use the VW Nozzles.
I don't think it would hurt anything.

I am using the Monark Nozzles for Mercedes in My Volvo Diesel and have has no issues.

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84 300D, 82 Volvo 244Gl Diesel

I sure wouldn't discard a car because I thought the compression was low. It could simply be your measurement method. It is critical that the compression gage displace the same volume as the injectors did (if going in the top). Some need a ring placed on the end to insure this. Re engine health, I would judge more by the blow-by. You can find videos.

Re pop pressure, I shoot for 1950 psi and am happy if all are within 50 psi, which is about the best I can resolve it, even recording a pressure trace electronically.

I think it is possible that the unheated WVO use is causing Piston Rings to Stick. There is several Threads on how and what people have dumped into the Cylinder and let that soak and over a long period of soaking.
There is a few People who have done that and had the compression go up afterwards.

The same has happned by switching to Synthetic Oil but it takes hundreds of Miles of Driving.

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84 300D, 82 Volvo 244Gl Diesel