I'm in need of parts for the injection pump's pneumatic governor in the '74 240D. There's a shaft that runs through the rear-most portion of the governor housing, the "Adjusting Shaft", a.k.a. "Poppet Cam Shaft". The Bosch part number for this piece is 1-423-004-000. My car's shaft and the bushings it rides in are worn to the point that side shake is causing a vacuum leak even with fresh o-rings installed. I'd like to replace this shaft and the bushings but am being told by several USA Bosch shops that the shaft is NLA as of years ago. The bushings were not offered as individual parts, only as part of the housing, which also is NLA. I've got a spare pump for reference, and these parts are just as worn as the ones on my car are. I suspect any used parts I find are going to be worn the same way. I want new parts.

I've found one of these shafts in stock and available from a vendor in Germany, but that's it. Nothing on the 'Bay. Struck out at the dealer (they supplied the entire rear governor assembly in the past). If I were to buy that shaft from Germany I'd still be hanging for the bushings. I can't help but think that I'm not the only guy who needs these parts for their car. I also wonder about future availability of these shafts. It would be nice to have a kit that includes a new shaft, new bushings, and fresh o-rings.

I am considering having a few shafts and bushings made by a local shop, but if the stuff is available and will continue to be so I won't bother with having any fabbed up. Before making a decision I'd like to hear other opinions. Maybe I haven't searched enough to find a vendor or some other option. Anybody know a for sure source for this stuff?

For reference, I'm talking about #55 in the upper RH corner of this diagram:

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

Is there one or 2 bushings?

What is wrong with the shaft?

I don't know how prevalent they are in metric sizes but it used to be you could buy generic bushings for things. They were usually longer then you needed. You would have to go to a place the specializes in bearings or look in the Granger or McMasters Karr (speling?) online site.

But you need to know what size you need.

I don't know if this is the case but in the old days when bushings were installed they were sometimes supposed to be reamed to size after installation.

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84 300D, 82 Volvo 244Gl Diesel

Two (2) bushings. One on either side of the cam, frictioned into the housing. I'll take some pics and post them tomorrow.

The shaft is worn badly where it's been pushed into the bushings. And of course the bronze bushings are worn and require replacemant, too. Note item #62 in that diagram above. It's a coil spring that tensions the shaft, thus pushing it into the bushings on one side. The wear is worse on the spring end of the shaft.

I've taken everything apart, cleaned up the parts, taken measurements of the shaft and bushings and made drawings for a machinist. I am looking into the possibility of finding standard bushings that could be modified - great idea there.

I don't think these bushings would require ream-to-fit tolerances. When I pressed them out of the housing they came easy. I doubt installing them causes meaningful deformation. Plus, the original bronze bushings were plated, maybe with nickel. This plating is present inside the bores except for where it's been worn off. This tells me these bushings were not reamed to fit the shaft.

I'll post some pics soon.

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

I might try an older injection pump repair place.They may have some of the parts in stock.

Thanks for the suggestion, Barry. At this point I've spoken with folks at four different shop in New Mexico, Utah, and California. Every one of the fellows I spoke with told me these parts are NLA. One of them told me he has a stash of the shafts but won't sell because he needs them for his rebuilding business. Can't blame him for that.

I'm thinking of limiting the time wasted by having some made up. And if I have some made up I'll have a few to pass along to others in need, saving them the pain of hunting and searching that I've been going through. It would be easy to bundle the gasket, o-rings, and bushings, along with the shaft.

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

Here's the pump, Bosch PES4M with pneumatic governor. These were used on OM615 (220D) and OM616 (240D) in W115 and early W123:


The parts I'm focused on, from the rear end of the pump:


And the wear points:



If you have a car with this pump and it ain't running right, emitting grey un-burnt fuel smoke, do a vacuum test on the governor system. If it leaks the most likely culprits are the diaphragm and this worn shaft and bushings.

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

so those parts just act on the idle dampener. the engine runs fine without it.
you could take out the loose parts and seal it up.

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1977 240D auto w/OM616.916 engine
2005 Matrix 5spd
2006 Prius

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Hmmm. One of the Bosch guys I talked to mentioned a different version of the same thing. His suggestion was to remove the control rod that comes down to the lever and let the coiled spring hold the lever and shaft, and the cam, in that position.

I'm not opposed to a mod. When I do that I prefer to maintain the ability to go back to stock if wanted. My inclination in this moment is to source a good shaft and bushings, put the thing back together with fresh o-rings, and pull the rod as suggested. That would give me fresh stock parts that would be easy to make seal, and they wouldn't wear out again. And if for whatever reason the car needed to be stock again all I would have to do would be to install the rod.

Plenty to think about. Thanks for the feedback.

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

And new owners need to be aware the pump has its own oil sump and must be changed independent of the engine oil. Synthetic 5W40, 15W50 or 20W50 is ok for these engines and pump as long as its Cx rated.

Back in the 1970's the recommendation for oil for the fuel injection pumps was single viscosity 40 wt.

The fist reasons for that were ounce that the oil in the pump gets hot and there is no Oil Cooler to cool the oil.

The 2nd is that in use the oil inside of the Fuel Injection pump becomes mixed with the Fuel that leaks by the plungers and barrels and contaminates/thins out the oil inside of the fuel injection pump. As the fuel mixes with the Oil in the sump the level rises and eventually goes out of the hole for that purpose and leaks out but as time passes there mix is more and more Fuel then oil.

The contaminates/thins out the oil inside of the fuel injection pump also means you need to periodically suck out the old oil (most don't have a way to drain the Oil) and replace it.

A Turkey baster with a tube on it is often used to suck the old oil out.

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84 300D, 82 Volvo 244Gl Diesel

I failed to find one of these "Adjusting Shafts', or "Poppet Cam Shafts", for sale anywhere in the USA. I searched the part number and found several vendors in a variety of countries showing the part number and description but none in stock.

So, I found a local machinist and had him make a run of 20 for me. It was relatively expensive to have one made, but only twice the price to have the 20 made.





One of these is now installed in my '74's injection pump with good used bushings and fresh o-rings, and the engine is running great. I removed the control rod and found, as others have noted, that the car runs fine without it. Typical German over-engineering to have a rod pull the poppet cam back from the damper and rack when the rack is already moving out of the way on its own.

I've also ordered up some oilite bushings from an industrial supplier and am waiting to see how good they fit the shaft and housing. If that's good I'll likely order up some o-rings and gaskets so I can put together a kit for those interested in having all the stuff needed to make the repair. These parts will likely be good for any Bosch PES4M injection pump with the pneumatic governor on them.

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

Pump shops themselves may be a good customer base as well.

'Tis a good thought, indeed. I appreciate it. I'll probably put some up on the 'Bay as they are and see what happens.

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

Thanks. Guys like you are critical to keeping these cars running long after M-B abandoned them. It is good for the earth to fix things and keep valuable resources in use, especially since these engines run fine on bio-diesel (no net-CO2 emissions), which I buy at the pump in CA (no conversion needed).

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Thank you, Bill! That's a fine compliment.

We'll see if there is a real need or desire for these reproduction shafts. I can have more made, if needed. The machinist I found is a talented guy who works from his home-based shop. I was blown away by how well equipped his shop is, way beyond what I expected. He likes doing these smaller scale projects for individuals and small businesses.

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- Greg -
1973 220D, The Prodigal Benz
1974 240D