I think you just missed my point in that burning too much fuel relative to air in a diesel causes higher temps...you say its running lean but say its been hot...the two are opposites. But yes, the IP could be out of whack to cause it.


These prechambers are probably well known about in other circles, its a shame I can't read German as their forums would probably shed some light on these interesting prechambers. The other ones I mentioned were actually much later now I think of it, as your ones are the old blunt end design not the round tipped ones.

__________________
1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

NZScott and Barry12345, I'm glad you guys chimed in. I've been scratching my head over all this and most likely over complicating everything along the way. My initial thinking was injection timing but after being told by some folks I think of as knowledgeable to consider mixture I've been doing my best to make it work out in my mind, and having a dickens of a time! I too believe(d) that more fuel = more power and that's it.

Now I understand where you are coming from NZScott, that more fuel means hotter temps (and power). I'm certain that my messing around with the governor setup was the root cause, but have had the problem backwards in my mind re: rich vs lean. I must say that more fuel makes sense considering the amount of power the car had on the highway. On my drive back from Utah it was holding its own on grades better than any other 240D I've experienced, and puffing a little black every now and then when putting my foot to it. Nothing seemed excessive, though, and engine temps stayed steady. Guess it was right over the edge in terms of how much heat and power the engine could take - not so hot that the cooling system couldn't keep up an overall balance, but hot enough in the chambers to cause some trouble.

Thanks for y'alls' thoughts and time! This has been a helpful conversation for me. I think I'm back on track now.

So why would two experts tell me to think "lean"?

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

He's right, you would have to have been over fueling to melt something in a Diesel engine. Diesels are lean burn by design, ie they always burn their fuel in an excess of oxygen.

So to melt the prechamber you would have to have been rich in that cylinder.

Nice documentation though, pictures showing the different chambers are cool.

__________________
2004 F150 4.6L -My Daily
2007 Volvo XC70 -Wife's Daily
1998 Ford F150 -Rear ended
1989 J-spec 420SEL -passed onto its new keeper
1982 BMW 733i -fixed and traded for the 420SEL
2003 Volvo V70 5 Speed -scrapped
1997 E290 Turbo Diesel Wagon -traded for above
1992 BMW 525i -traded in
1990 Silver 300TE -hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold

Yeah, I get it now.


I'm sure all 4 were rich, thanks to my meddling with the governor. Why would #4 be the one to let go? Hotter in the rear end of the head by nature? Something different about that injector, like that needle tip couldn't take the higher heat, came off, and the bad spray pattern did the rest?


Thanks! Pictures help tell the story, and if my experience helps others, here it is.

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

Just out of curiosity, did the pump shop say how far it was out? or which was it was? Rich or Lean?

__________________
2004 F150 4.6L -My Daily
2007 Volvo XC70 -Wife's Daily
1998 Ford F150 -Rear ended
1989 J-spec 420SEL -passed onto its new keeper
1982 BMW 733i -fixed and traded for the 420SEL
2003 Volvo V70 5 Speed -scrapped
1997 E290 Turbo Diesel Wagon -traded for above
1992 BMW 525i -traded in
1990 Silver 300TE -hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold

No, and at the time I didn't think to ask. I had everything figured out, right?

He said the pump was in good mechanical health, the elements were good and that all four were delivering very close to the same amounts as they were, and that the existing diaphragm was fine to keep using (soft, pliable, no tears or cracks). I gave him the governor spring and shims I had from the extra pump. He tested my rebuilt lift pump and it passed both pressure and suction tests. I think the only adjustment involved was setting the governor up.

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

Just following up on this old thread. I FINALLY got around to installing the re-calibrated injection pump and the car is back on the road. Engine seems fine. It sure is nice driving the old W115 after a year sitting in the garage.

Thanks again to everyone who chimed in and helped set me straight on how lean/rich in a diesel gives different results than in a gasser.

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

My experience is mostly non Mercedes, but I've seen a single diesel nozzle fail and ultimately concluded that it suffered poor manufacturing or metal fatigue. Lasted a long time, but eventually gave up the ghost. Very interesting thread. Thanks for posting.

__________________
DS
2010 CL550 - Heaven help me but it's beautiful
87 300D a labor of love
11 GLK 350 So far, so good
08 E350 4matic, Love it.
99 E320 too rusted, sold
87 260E Donated to Newgate School
www.Newgateschool.org - check it out.
12 Ford Escape, sold, forgotten
87 300D, sold, what a mistake
06 Passat 2.0T, PITA, sold

Las Vegas NV

My schedule did not allow for me to do some work last year on one of my diesels.I took it to a mechanic that I have known for years. He made the same statement about lean. A gasoline engine uses unburnt fuel to remove heat. Running lean causes temperatures to skyrocket. With this high temperature, you will experience detonation which is the fuel expanding too early in relation to top dead center. In a diesel engine, the fuel is not added until just before top dead center. So another words it's not hanging around in the cylinder and getting lit off early due to detonation because it's not been injected yet. That is what allows the extreme cylinder pressures inherent to a diesel. The fuel simply has not been injected yet, and cannot detonate.

Wrong fuel in a fuel vendors tanks is not impossible. If possible fuel at busy truck stops or at least a fairly high volume sales place. A gas diesel fuel mixture could have done this.


My issue with smaller volume fuel sellers. Many are supplied with non dedicated tankers. You thought you had more power is almost a giveaway.


Although there is no certainty some fuel issue was a possibility.

Following up on this, I now believe that the problems I was having with this engine came down mostly to over-fueling caused by a vacuum leak in the governor. And what really bites is that the local injection shop that checked out the IP for me either missed or failed to tell me about any problem with the governor. Assuming they checked the IP on their test stand, I find it hard to believe that they missed the leaky governor. I did ask them to replace the governor diaphragm, but they told me it was not necessary, that the diaphragm was bueno. And they were right about that. But something else wasn't right . . .

After getting the IP back on the engine and timed the car was running pretty good, but after driving it more I could tell that something was still not quite right with the injection system. It still was nailing and puffing grey smoke, and power output was "bouncy" and inconsistent at mid-throttle cruising speeds. The grey smoke led me to believe that I hadn't timed it right, that timing was behind, so I advanced timing enough to more or less eliminate the grey smoke. I didn't measure how far I advanced the timing, but it was a lot. And even then it was still nailing under some conditions, and the bouncy power output didn't change. A friend suggested that I should check the governor system for a vacuum leak, and sure enough I did find a leak.

The leak was caused by wear to the adjusting shaft and the bushings it rides in, in the rear-most portion of the governor at the back of the IP. I've since replaced the shaft, bushings, and o-rings. I also re-set injection timing to spec. The engine now is running better than ever, consistent with the performance and feel I get from the rebuilt engine in the '73. I'm going to keep driving it and we'll see how well it works out. At this point I feel confident that I've fixed it.

And to better tie things together, here are two threads I started related to this journey:

Parts for Pneumatic Governor, OM615 and OM616

Adjusting Shaft, Reproduction - Replaces Bosch 1 423 004 000 1423004000

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

Pre-ignition because you don't have control when that leaking oil starts to burn and it would ignitie much faster than the injected fuel.

I remember reading in a service manual that if you notice damage to prechamber you should check the diaphragm on the ip.

Yep, or first check the governor's ability to hold vacuum, before taking anything else apart. The problem could be with the adjusting shaft for the poppet cam, and not with the diaphragm, like it was in my car.

Hopefully all my typing and posting will save other people the trouble of finding things out the hard way!

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

Thank you for following up. This was an interesting thread(s).

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

No. If a diesel is consuming that much oil it would be MASSIVELY smoking.