If you get too much smoke, you could turn back the full-load stop on the pump, it will inject less diesel at full-load.

You can check the diaphragm with a vacuum gauge, or with your thumb. With the engine off, take of the vacuum line at the diesel pump. Remove the cable from the starter knob. Now move the lever into the stop position (to the front) and keep it there. Put your thumb over the open vacuum connection of the pump. Put the lever back in the normal (drive) position. Now remove your thumb. You should hear a click when the control rod moves back. You can check it while holding your thumb for longer periods.

With a vacuum gauge it is the same, but connect a vacuum gauge instead of your thumb. You should read around 90 mbar of vacuum if you put the lever back into the normal position.

If it doesn't hold vacuum, it is usually the axle of the poppet cam (at the back of the governor, inside red line in picture below) which leaks. You can buy a new cover (including poppet cam, inside blue line in picture below) or just replace the axle seals (but you must find the parts from a diesel service company).

How did you try to adjust the timing of the pump? And did you succeed?

How is general maintenance? Air filter clean? Adjusted the valves recently? Diesel filter new?

 

Hi Thanks so much for the help. Do I understand rightly that it won't hold vacuum with the engine simply shut off? If the injector pump is leaking air, than I find it odd that the idle isn't high. I wouldn't think that an over-fuel condition would tend to raise engine speed even if it is starved for air (limited by throttle position). The engine speed certainly increases if I remove (or crimp) the line from the throttle body to the fuel injector pump.
It smokes (white-gray) at all times, but it's worse at idle than freeway driving. What are the "axle seals"? I thought that if it is leaking it would be the diaphram.
Now I have a "dumb question." What does the vertical rod (and lever) that connects from the throttle to the fuel injection pump do? Since fuel delivery is being controlled indirectly through partial engine vacuum this connection to the injector pump and purpose isn't clear to me.
Thanks,
Greg

 

The vacuum chamber of the governor should hold vacuum with the engine off, check by the thumb/vacuum gauge method described above.

If the vacuum chamber is leaky, the accelerator pedal is usually not pressed deeply enough to prevent overspeeding, but there is enough air or the engine has to work to suck in air. The idle has to be high too, above 800 rpm, if the valve in the air intake has not been adjusted (you can adjust the valve in the air intake, by closing it more, more vacuum is created to compensate for the leaky vacuum chamber).

Here you can see a diagram of the vacuum chamber, nr. 10 is the diaphragm. Nr. 12 is where the air hose is connected. Nr. 15 is the poppet cam, at idle it is moved into position 15b, at full load it is in position 15a. The rod controls that. It prevents the engine from "loping" or "sawing" (an unsteady idle) at idle and low speeds. The axle of the poppet cam can leak (quite common). Other possibilities are the gasket between poppet cam housing and the connection of the air hose and of course, the diaphragm.

 

OK, I think I'm begining to understand; thanks! However, I only see a position 15a and 15t; I don't see a 15b. I assume that 15b is where the cam is shown and 15a is the "shadow" line where it would be retracted? It would seem to me that the retracted position would be at idle (moving the shaft in the same direction - right, as vacuum). Am I looking at it wrong?

These parts look like they're serviceable with the injector pump in place, without requiring removal; is that so?
Thanks again,
Greg

 

15t = 15b, part of the b fell away. 15b is the idle position, 15a (shadow line) the full-load position.

The governor is indeed servicable with the pump on the engine, but be careful, parts can fall out.

If you want to read more, see here:
07.1 Diesel Injection System - OM616
Select 07-010 (section A)
and other links with "pneumatic" in them. It is the Service Manual of the W123, but it is applicable on the W115-220D.

 

I've located a vacuum gauge and will check it tonight per your instructions, but I'm pretty confident that it will come up leaking since my primitive test of sucking on the tube tells me it leaks. I just got off the phone with a MB dealership and he said "come in with your vehicle vin and Bosch injector part numbers and I'll show you what's available, but there isn't much." Not very encouraging. I know you're in Europe, but do you know of a company from whom I could obtain these parts? If it leaks I presume your advice would be to replace the entire cover and see if that solves the problem? (if not it's likely the diaphram then?)
To answer an earlier question, I did adjust the valves (they were all tight). I adjusted the injection timing by loosening the bolts that hold the injection pump and rotated the pump a little away from the engine. It didn't help so I moved it back. Not terribly technical I know, but the "onset of injection procedure" in the Haynes book was very poorly written and described and I don't have the little spout tool, so I figured if the timing is retarded due to wear and chain stretch then a little movement in the presumptive right direction should help if that is indeed the problem; it didn't help.

 

How did you check exactly with the vacuum gauge? Disconnected the air line at the pump, push lever into the stop position and held it there, connected vacuum gauge and released lever? If no vacuum is measured, than there is a leak.

The next problem is establishing where the leak is. It could be the axle of the poppet cam or the diaphragm. If you douse both sides of the axle of the poppet cam in oil (so that air cannot leak there) with running engine, you should notice a reduction in rpm if the leak is there. Sometimes you have to move the poppet cam a bit so that the oil seals the axle. You can also try the vacuum gauge test with the engine off.

Of course a leak at the poppet cam does not rule out a leaky diaphragm. Both can leak at the same time.

You can replace the entire cover or replace the axle shaft seals. The first solution is more expensive, the seal replacement is more difficult but cheaper, especially finding the parts required. The parts numbers of the axle shaft seals are:

Name--------------------bosch number-----------quantity required
VERSTELWELLE------------1 423 004 000----------1
SINTERBUCHSE------------1 900 301 012----------2
AUSGLEICHSCHEIBE--------1 420 100 012----------4
SCHENKELFEDER-----------1 414 651 060----------1
O-RING------------------1 900 210 105----------2
SICHERUNGSSCHEIBE-------2 916 080 910----------1
DICHTPLATTE-------------1 420 034 010----------1

The MB part number for the entire cover is A0000750004, I don't know the Bosch number. If the MB dealer doesn't have one, try a (Bosch) diesel service station. If you're lucky, they have the cover and are happy to get rid of it, as these pneumatic governors are not used anymore. The Bosch website has a search facility for diesel service centers and service dealers:
Finding a Service Center for Car and Truck Repair
Other diesel repair shops can help you too if they have Bosch parts.

The injection timing can also be checked using the well-up method. Turn the engine so that it is at around 30 degrees BTDC in the compression stroke of the first cylinder. Remove the steel injector line of the first cylinder at the pump. Now slowly move the engine degree by degree (an extension is advisable) and watch the open pipe connection. If diesel starts to well up, read the position of the engine. That is the start of delivery. It is not as accurate as the overflow method, but it is easier. Simply moving the pump by hand isn't advisable, slight movement of the pump can have major impact and can cause engine damage. By the way: you can make the spout from an old injector line.

Oil in the throttle body is usually caused by oil in the blow-by air coming from the ventilation on top of the valve cover. The air filter should be filled with oil up to the level indicated inside. Don't overfill, as the engine can suck in the oil and can run on that oil and that can cause a runaway engine in the most extreme case.

 

That's lots of useful information; thanks again. Yes, I did the vacuum procedure as you outlined. I have some really thick oil that should work nicely to seal the poppet shaft seal to redo the test and perhaps check the engine running also.
What do you mean by turning the pump by hand? I didn't even know there was some place one could turn the pump. Would you mind summarizing the "over-flow" method? And I am right that rotating the pump away from the engine advances the injection timing?
Thanks again,
Greg

 

Something new to report: I applied oil to the poppet shaft and it made a big difference in the vacuum test. Where before it would read something like 20 torr when I released the lever and within seconds blead down to zero, now it jumps to about 70 torr and very slowly drops. This is inspired me to run the engine. Unfortunately no change: a whole lot of white-gray smoke which smells of unburned diesel fuel. This inclines me to think that though the shaft seals do leak, they're probably not leaking fast enough to create the problem. It seems more and more like it might be very retarded timing. Is it possible that the injection pump gear somehow jumped a tooth? The thing I don't get is that the problem has gotten steadily worse. I don't see how the timing could be "slipping" over time. If it's off it would seem like it would be off and not progress. THis is quite aggrevating. I will check the "well-up" timing method this weekend.
Greg

 

By turning the pump I meant swivel the pump, like you did.

You can check the timing chain stretch by putting the camshaft exactly on its mark:

and than reading the position of the crankshaft

In this case about six degrees late. More than six degrees is not good and the timing chain should be replaced.

Jumping a teeth is not very likely, unless you turned the engine in the wrong way or used the camshaft bolt to turn the engine. Timing chain stretch is was normally delays injection timing and valve timing.


The overflow method.

You start by cleaning your diesel pump, use brake cleaner, toothbrush and such like so that there is no dirt on the outside. Remove the securing bolt with the two half moons that is inbetween the pipe connections.

Move engine to about 30 degrees BTDC in the compression stroke of cylinder 1.

Remove the injector line from cylinder one. Here you can see the pipe connections without the injector lines. You need only to remove the first line at this stage. It is a slightly more modern MRSF pump, but the principle is the same. Remove the securing bolt with the two half moons that is inbetween the pipe connections.

Now unscrew the pipe connection and carefully lift it out, now you can see this:

Take a pair of pliers (clean it first thoroughly with brake cleaner or something similar) and carefully remove the spring.

Now you can see this, the delivery valve in the delivery valve holder and a copper seal ring.

Use the pliers to remove the delivery valve

And store both spring and delivery valve in a safe and clean spot:

Now you see this, the delivery valve holder and the copper ring.

Make sure it is somewhat in the middle, screw back the pipe connection and torque to about 30-35 Nm. Screw on the spout.

Start and keep pumping the hand pump and watch the spout. When it drips about 1 drip a second, it is the start of delivery. If it is flowing, the engine has to turn further. If it doesn't drip, start of delivery has passed.

Here is a youtube movie, not entirely perfect, but you get the idea of the dripping. I was hand pumping and filming at the same time, I swivelled the pump some more to get the correct dripping.

Normally the diesel will flow at 30 degrees BTDC. Now turn the engine a degree at the time until diesel starts to drip at 1 drop a second. Now read the position of the engine on the harmonic balancer. If adjustment is necessary, unscrew the three bolts, the bolt at the back of the pump and the hard injector lines. Swivel the pump to adjust, towards the engine advances the start of delivery; from the engine is a later begin of delivery.

When you start pumping the handpump, fasten a bolt of the diesel pump, otherwise timing might be affected. If correct fasten the other two.

There should not be pressure on the hard injector lines when you screw them back on. Bent them by hand and carefully.

Now the spout can be removed. Unscrew the pipe connection. Renew the copper washer (get one at the MB dealer, do not use a generic copper washer) and you might want to renew the rubber O ring around the pipe connection. Put back the delivery valve and spring. Screw the pipe connection into place. Now you need to torque it, that is essential. First torque to 30 Nm, than loosen it. Torque it again to 30 Nm and loosen it. Now finally torque it to 35 Nm. Put back the bolt with the two half moons.

 

By turning the pump I meant swivel the pump, like you did.

You can check the timing chain stretch by putting the camshaft exactly on its mark:

and than reading the position of the crankshaft

In this case about six degrees late. More than six degrees is not good and the timing chain should be replaced.

Jumping a teeth is not very likely, unless you turned the engine in the wrong way or used the camshaft bolt to turn the engine. Timing chain stretch is was normally delays injection timing and valve timing.


The overflow method.

You start by cleaning your diesel pump, use brake cleaner, toothbrush and such like so that there is no dirt on the outside. Remove the securing bolt with the two half moons that is inbetween the pipe connections.

Move engine to about 30 degrees BTDC in the compression stroke of cylinder 1.

Remove the injector line from cylinder one. Here you can see the pipe connections without the injector lines. You need only to remove the first line at this stage. It is a slightly more modern MRSF pump, but the principle is the same. Remove the securing bolt with the two half moons that is inbetween the pipe connections.

Now unscrew the pipe connection and carefully lift it out, now you can see this:

Take a pair of pliers (clean it first thoroughly with brake cleaner or something similar) and carefully remove the spring.

Now you can see this, the delivery valve in the delivery valve holder and a copper seal ring.

Use the pliers to remove the delivery valve

And store both spring and delivery valve in a safe and clean spot:

Now you see this, the delivery valve holder and the copper ring.

Make sure it is somewhat in the middle, screw back the pipe connection and torque to about 30-35 Nm. Screw on the spout.

Start and keep pumping the hand pump and watch the spout. When it drips about 1 drip a second, it is the start of delivery. If it is flowing, the engine has to turn further. If it doesn't drip, start of delivery has passed.

Here is a youtube movie, not entirely perfect, but you get the idea of the dripping. I was hand pumping and filming at the same time, I swivelled the pump some more to get the correct dripping.

YouTube - Timing MRSF diesel pump on a Mercedes-Benz OM616 engine

Normally the diesel will flow at 30 degrees BTDC. Now turn the engine a degree at the time until diesel starts to drip at 1 drop a second. Now read the position of the engine on the harmonic balancer. If adjustment is necessary, unscrew the three bolts, the bolt at the back of the pump and the hard injector lines. Swivel the pump to adjust, towards the engine advances the start of delivery; from the engine is a later begin of delivery.

When you start pumping the handpump, fasten a bolt of the diesel pump, otherwise timing might be affected. If correct fasten the other two.

There should not be pressure on the hard injector lines when you screw them back on. Bent them by hand and carefully.

Now the spout can be removed. Unscrew the pipe connection. Renew the copper washer (get one at the MB dealer, do not use a generic copper washer) and you might want to renew the rubber O ring around the pipe connection. Put back the delivery valve and spring. Screw the pipe connection into place. Now you need to torque it, that is essential. First torque to 30 Nm, than loosen it. Torque it again to 30 Nm and loosen it. Now finally torque it to 35 Nm. Put back the bolt with the two half moons.

Hi Again, I checked the chain stretch as you directed, aligning the notch on the camshaft washer with the mark in the camshaft bearing support, then checking the crankshaft pulley timing marks. It was no more than 2 degrees off.
I then checked the onset of injection using the well-up method you described earlier. Boy it is tough to see since the volume is so tiny, but it's 15 deg BTDC at earliest. THe problem I have is that the injection pump is swiveled as far up as it goes (closest to the engine). So do you think this is the root of my problem? How did the timing change? Why has it gotten progressively worse if the chains not stretched?
Thanks again,
Greg

 

OK, I have an odd-ball thought. I told you earlier that I adjusted the timing of the injection pump before but it did no good so put it back. Is it possible that when I loosened the three bolts holding the pump and moved it that there was enough play that it skipped a tooth then? Hmmm.... very confusing.

 

I repeated the well-up method several times and I seem to get a little better at it each time. When I note the fuel just begining to well-up in the injector I check the timing marks and it's just past 15 deg BTDC (before 10 deg BTDC). I'm tempted to pull the pump out and reinstall in order to be able to have some adjustment. Do you think this is wise, or should I try the other method (drip spout) before I do this?

 

Normally the well-up method is helped by screwing a thin, thermometer-like tube on the pipe connection, so that you can see the diesel rising more easily. The well-up method is less precise than the overflow method. The question is whether the 15 BTDC is correct, if so, that can explain the smoke. Diesel injected at 15 degrees BTDC cannot warm up and ignite. If you want to be sure, get a spout (MB part # 636589022300) and do the test again. Alternatively you can use the well-up method to put the begin of delivery at 24 degrees and see if that helps. A slight warning: diesel injection advances too much leads to high temperature and stress on the engine (piston is still moving up while the diesel ignites and push down on the piston). If you take the pump out, you might want to use a new gasket. If it really is at 15 degrees and the pump is swivelled to the engine (have you removed the bracket at the back of the pump?), than the pump has to come out and put back so that you have room to swivel.

If you do get a spout (or make one), you can also check the pump by testing the begin of delivery of cylinder nr. 4. There should be no more than 2 degrees difference.

Leaves the question how the pump moved from 24 degrees to 15 without a stretched chain. The worst I've seen is 19 degrees on a 300TDT. I don't know the answer to this one. Maybe the injection timing device is not working properly?

Skipping a teeth is not really possible unless you pull the pump out of the engine.

How many miles are on the engine?

 

The odometer stopped working many many years ago, so I really don't have a clue. This is the second of 3 MB diesels that my Dad owned. The first was a 1964 190D - that had a lot of miles on it. He bought this one used and a few years later bought a 300 TD. By then the 220D wasn't driven much. He passed away 9 years ago and the 220D has just sat with my brother starting it once a month to "keep the juices flowing" until I started driving it about a year ago.

Thanks for the comment on the gearing of the pump. If I pull it out I'll have to take a good look. I don't really understand how it can be geared to the intermediate shaft and turn in the same direction, but of course you're right. Thanks for the diagram, but I'm really not sure what I'm looking at. I moved the pump yesterday afternoon to confirm it (can't help myself!); I checked the timing after moving the pump away from the engine and it was at about 0 deg TDC.
Greg

 

This is how the chain runs through the engine:

98 is the timing device, which is connected to the intermediate gear shaft, which drives the injection pump. If the crankshaft turns to the right, the intermediate gear shaft turns to the right.

This diagram shows the intermediate gear shaft:

98 is again the timing device, just above 94 you can see the chain. 111 is the diesel pump. It is slightly different with your engine, because the diesel pump has its own oil and is not provided through the engine oil circuit, but the principle is the same. The diesel pump is connected directly on the intermediate gear shaft.

Starting engines and not running them until warm is not good for engines. The oil becomes very acidic.

 

OK, I get it! Those are splines on the end of the injection pump not a spur gear! I doubt that you'll be back here until tomorrow, so I probably should have asked this earlier, but are there any pitfalls to avoid in removing and reinstalling the injection pump? Any special hints to get it right?
Thanks,
Greg

 

It is not a spur gear, the pump is driven by a coupling sleeve over the splines.

There might be a rubber O ring on the axle of the injection pump that needs to be replaced and a new gasket is also advisable to prevent oil leakage.

The shaft of the pump needs to be free of oil and grease.

Take the pump out on 24 degrees BTDC and look if the marks on the pump line up when you take it out. That gives you an indication of whether timing of the pump was off the mark.

Also cover the open pipe connections of the pump with same plastic cling film (or special plastic caps) to prevent dirt entering the pump.

 

Thanks for the tips. I pulled the pump out and to my surprise the splines on the coupling bolted to the injection pump are internal, not external as your diagram and my book have it. I could not make out any similar markings or gap in the splines as your diagram shows. I simply put the pump back in but a little lower than I removed it. I then put things back and checked the onset of injection timing. I managed to get it right around 24 deg BTDC.
The bad news is that after putting everything back together it still smokes - a lot; marginally less than it did before and it does have more pep, but it still smokes. AGGRAVATION!!!!!!!!!!
Reflecting on the situation, I bet the fuel timing has been wrong for a long time. The same guy who elected not to refill the oil in the air filter probably was responsible for the bad timing. I keep "fixing things" that are wrong but are not the source of the problem.

 

Maybe I need to go back to thinking about the injectors. I don't have a neat hydraulic pump with a 20 bar gauge on it, so to test the injectors I simply attached them one at a time to the # 1 nozzle and connected a remote starting switch to the starter and observed the spray pattern, force of spray etc; all highly subjective I know, but I would recognize an odd spray pattern or a clogged injector or a leaky one. THey all delivered a small but forceful stream straight down. I caught the fluid in a dish and they all delivered enough fuel to aerosolize a little bit of diesel fuel as the stream struck the dish. I also tested three injectors I removed from a 240D at a junk yard in the same way. They behaved similarly. Am I kidding myself here? Should I buy new injectors or get a hydraulic tester? Any other thoughts of what could be at fault here that is slowly getting worse all the time? After each service I've performed I get marginal improvement but the trajectory of performance is downward.
Thanks,
Greg

 

Yes, I meant 200 bar not 20. An order of magnitude issue, probably because I really think in pounds per square inch, not bar or Pascal.

That makes sense about the splines. Silly me, I read your post when you mentioned the collar, but I was still expecting to see a male and female part rather than two external splines with a collar joining them. Oh well, despite my misapprehesion this adjustment seemed to go OK.

I will fiddle with the idle at lunch hour. Some weeks ago when this problem began to appear I had raised the idle since I found it smoked less at a higher idle, but had rather optamistically turned it back this weekend thinking that I wanted to reset everything to "normal."

Yes, there is the leaky pneumatic governor situation, but I found that when I put the viscous oil on the poppet shaft it did help it hold vacuum, yet made no perceptible difference in how the engine ran. This inclined me to believe that this is really not a problem, even if it could be better.

The flow from the injectors is conical but very tight, to the point that it appears to be a straight stream, isn't that right? This is how it appears to me on the video I've seen anyway (and how it looked when I connected the injectors). If it was indeed coming out as a solid stream I can't imagine that it would be straight down; wouldn't it be directed to one side of the other since the nozzle opening creates this cone when the tip rises out of the whole in the nozzle when the pre-set pressure has been achieved? If it were a solid stream that would mean it was only coming out on one side of the nozzle or the other.

Yes, I do realize that I'm rather handicapped because I don't have proper test equipment, so I'm relying on observation and inference (and I'm too cheap to take it in to the shop .

Thanks again for the advice; I will persevere.
Greg

 

I will fiddle with the idle at lunch hour. Some weeks ago when this problem began to appear I had raised the idle since I found it smoked less at a higher idle, but had rather optamistically turned it back this weekend thinking that I wanted to reset everything to "normal."

Yes, there is the leaky pneumatic governor situation, but I found that when I put the viscous oil on the poppet shaft it did help it hold vacuum, yet made no perceptible difference in how the engine ran. This inclined me to believe that this is really not a problem, even if it could be better.

You've established with a vacuum gauge that the governor doesn't hold vacuum, that is a problem. That will cause smoke and diesel not being burnt because of lack of air.

What happens is the following. Under normal conditions you have to open the air valve half way and than the engine runs at let's say 3000 rpm. If the governor cannot hold vacuum, you only need to open the air valve for a little bit for the engine to run at 3000 rpm. The problem is that the air valve doesn't let enough air through to the cylinders, but the amount of diesel injected is still the same.

Good to hear that the compression is in order. Did you check with the air valve completely open?

If you have checked through the injector openings, don't forget to use new heat shields under the injectors.

 

You are shooting in the dark. Do the compression test before you go any further. Anything below 300 p.s.i. is suspect.

 

Thanks Mike, yes I was thinking last night that I need to get the tool (I have a compression tester for gasoline engines but doesn't fit diesels) and do that to rule it out. Low compression was not my first thoguht because it starts so easily, but there's nothing like some hard data.
Greg

 

Ok. Now you know; compression is good, valves are not burnt, head gasket is not blown and it is not an internal engine mechanical problem.

Next step. What did you determine the pump timing to be? You must check the pump by either drip or rise method at the #1 compression stroke. I'm guessing you are but make sure you are on the compression cycle. Pull the valve cover and check. (turn the crank until the #1 intake valve opens then continue turning to 24-30 degrees BTDC).

 

...i just want to say that both of you guys are an asset to this place, the exchange of knowledge between you is most respectable and invaluable. :bowdown:

 

The diesel engine has a tendency to run out of control even with a limited amount of diesel injected, certainly if there is no load on it. If that happens, air flow increases, vacuum increases and less diesel is injected. It is a feedback loop. Feeding a constant vacuum to the governor doesn't work.

That is also why there was less smoke at 3000 rpm. Only a limited amount of diesel was injected, but the speed of the engine wasn't controlled by the governor. At 3000 rpm more air is drawn in, but the amount of diesel was still low.

The oil seal on the poppet cam shaft is temporary, and sometimes it will take a while to make the seal. The puppet cam shaft isn't the only place where it can leak, the diaphragm can leak too.

 

Hi Govert,
OK, that makes a lot of sense to me. So, what would you do, replace the cover with all its parts and then see if things are OK and if not have the injector pump diaphram replaced? I presume that is not something I could likely do myself, but would have to have done professionally.

One thing I did notice with both a hand vacuum pump and my little lab vacuum pump is that I couldn't get a good vacuum on it even with dousing the poppet cam shaft seal with oil. The fuel shut-off lever test that you described worked fine with the oil, but actually pulling a vacuum didn't go above 10 inches of mercury (250 torr or 330 mbar), If my recollection is correct. I didn't keep the vacuum on it that long not knowing if I could do harm to the unit if it never experiences high vacuum. Would you expect the vacuum to keep rising? Do you think this indicates a leak elsewhere (like the diaphragm?) or have I simply overcome the film strength of the oil on the shaft?
Thanks,
Greg

 

Or does it? The piston speed increases when the engine speed increases, but does that mean it can suck in more air through the closed air valve?

I recently worked on a OM616 engine with a governor with no leaks at all. I did the vacuum test: removed air hose, pushed lever in stop position, connected vacuum gauge, released lever. The gauge showed slightly below 100 mbar of vacuum and that is what you should expect. The FSM says 70-90 mbar, see:
07.1 Diesel Injection System - OM616
and select 07-125 over there.
I can make pictures or a movie this saturday of that governor, for comparison.

If you connect a vacuum pump to the governor, and if there are no leaks, the vacuum can go as high as the pump can provide (usually around 800 mbar of vacuum). It will not damage the governor, you are doing the same thing as putting the engine into the stop position.

According to my information you cannot get the engine to run well with a leaky governor housing. A slow leak is acceptable, but we are talking half a minute/minute here.

You can replace the diaphragm yourself, it is very well described in the FSM. You do need a micrometer and you have to watch out for small parts.

(That is my hand)

Fixing the diaphragma to the control rod is the most difficult, but do-able.

 

Hi Govert,
I assume your "or does it" refers to whether the engine can draw in more air? From what I can tell these engines's butterfly valves do not limit air flow nearly so much as in a typical gasoline engine. For one thing they still draw air through an ostensibly closed butterfly even though there seems to be no bypass - you can feel the air flow around the edges of the disc. Also the pneumatic line from the injector pump is attached to a channel in the throttle body which is open to both sides of the butterfly valve which has a notch cut into to it to accomodate this channel. I think a lot of air must be able to pass through this channel. This also suggests to me that the vacuum remains relatively low in this line. Besides all this the shear volume of air from the tail pipe of an idling diesel is amazing - even these engines with throttle bodies.

Can you tell me what the part number is for diaphragm? and do I need to pull the pump out (please say no )

Thanks,
Greg

 

I was doubting my own words whether more air per stroke is sucked in with increased engine speed.

The channel in the throttle body is the venturi, that produces the vacuum. If you open the air valve the venturi is bypassed, so the vacuum decreases.

The pump can stay on the engine to replace the diaphragm, but there is not much space to work in a W115, but it is possible.

I held my hand for the air intake of a idling W115-200D, the amount of air sucked in was considerably less than with my W123-200D, which does not have a air valve.

I have to look up that part number, MB sells them, but other manufacturers too, sometimes at lower prices.

 

Thanks Govert, I'd appreciate that very much. So far I'm not impressed with MB dealerships parts departments, but I may be premature in my judgment. Also I've tried searching the internet for the part number of the cover and so far no luck. Do you have internet suppliers that you recommend?
Greg

 

The MB part number for the diaphragm (or membrane) is A0000750607

The MB part number for the poppet cam cover is A0000750004
That number isn't know in the Bosch catalogue, probably because the poppet cam cover doesn't have a single number in the Bosch catalogue. I do include two PDFs from the BOSCH website: Bosch Automotive Tradition which lists all the parts of the pneumatic governor and an exploded view. It is in German, but the Bosch parts numbers are there. You might want to go the way of replacing the axle seals yourself, that is cheaper than buying the entire cover ready made.

The MB part number for the gasket between poppet cam cover and the rest of the housing is A0010742380

Although my friendly neighbourhood Mercedes-Benz dealer is very good (I was at the parts department once, said that a wanted a certain part number. Upon hearing the number the man helping me said: "that is that rubber hose for the engine ventilation") I always look up the numbers in the EPC (Electronic Parts Catalog) first. For Americans access to the EPC is free, look here for more info: EPC-net Online

If you want to keep the car and work on it yourself, get a Factory Service Manual, that has a ton of information.

I know only one internetsupplier Auto Parts at AutohausAZ - OEM Auto Parts - Discount Replacement Parts, Resources and Car Care Tips but I don't think it has these parts.

 

Hi Govert,
I'm having a devil of a time finding the parts you specified. The MB dealership says that they're all back order items from Germany without an arrival time, meaning they may or maynot be available.

The Bosch link you gave me earlier has a dealer finder but the dealers are independent foreign car repair shops. I called a couple and they have only limited access to Bosch parts. From the diagram you posted it looks like the shaft seals are simply O-rings (also how they're identified on the parts list you gave me earlier). Might I be able to use any good quality nitrile O-ring of the proper size? The diaphragm is going to be harder of course; no such thing as a generic or standard diaphragm. I have a couple of e-mails into diesel parts suppliers on the US east coast who do carry Bosch equipment, but I won't know until they reply.

One question I had about the poppet cam operation: you've identified "b" as the idle position and "a" as the full load position, but it appears that "a" is the retracted position and the same direction (right on the diagram) that vacuum pulls toward. I think I must be looking at this thing wrong somehow.
Greg