Have you considered this issue?
http://www.peachparts.com/shopforum/vintage-mercedes/223548-what-symptoms-bad-ip-governor-diaphragm.html

74 240d Grey smoke questions

1973 220D W115 Injection Pump Gasket - Mercedes-Benz Forum

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I just put in a brand new IP diaphragm at the beginning of September. I've recently pulled a vacuum on the governor and it is still airtight.

The car started smoking a bit more under a load proportionally to our altitude gain on the trip across the country. Just west of Tucumcari, NM it blew out a ton of carbon but otherwise has been working pretty well when warmed up.

When I start it, the engine has some up-down-up-down sawing but it only does that for about 30 seconds after first starting it up. That's not really the issue but I thought I'd mention it. Startup is a bit rough but its down around freezing almost and the high altitude can't be helping.

Anyway, the day after we got to New Mexico I did a valve adjustment and a diesel purge.

Right now I'm getting ~27mpg and when I was in the northeast before leaving New Jersey, I got upwards of 34mpg. I think I also had access to much better fuel (I was burning B20 or B30 all the time there) and New Mexico has probably already switched to winter diesel.

At the lower elevation, the car didn't smoke either unless I really got into the pedal but then it was only a slight amount. Granted, that's also a function of the B20 and its better combustion properties. There are TWO biodiesel pumps within 100 miles and soon I'm going to go fill up there. I may take a few diesel containers as well and get 15 more gallons for the future. I wish I had a secondary tank...

So my fuel mileage data set is variable with regard to fuel type but I always dose the tank with the appropriate amount of cetane boost so there is a constant. I've burned through three full tanks since I've been here and fuel mileage has been constant. I know I'm only staying for another five weeks but I don't want this stuff building up on my pistons, valves and coking up my prechambers.

By the way, my coolant level is fine and there is no oil or grime in it. My timing chain is stretched just about 5deg but 2700 miles ago when I had a very reputable indy mechanic in NJ fully check over the car as well as do an oil change, he said the timing chain was fine and didn't need replacement. When i did my recent valve adjustment, I checked the chain stretch against the camshaft notch and the crankshaft and it was still about 5deg.

Surely Mercedes had a high altitude compensation procedure for these cars back when they still went to the dealers for maintenance regularly.

Thanks all.
Phil Forrest

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1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson

I'm not 100% sure about my understanding of this diaphragm system but I guess in a way it does have altitude adjustment because the governor is "governed" by the differential pressure at the diaphragm. Whilst you will have less dense air at higher altitude that is a constant factor on both sides of the diaphragm.

However, I guess there'll be a point where the stiffness of the diaphragm and the mechanism that is attached to it plays a greater roll in system - I can imagine that as the air gets thinner and thinner - you just won't get the deflections you'd need for the system to operate...

...but then I guess the air would be so thin that you'd end up with combustion problems - as in there just isn't enough oxygen content to make a decent bang.

So moving on from my ramblings => You could try putting in a lighter weight oil in the IP (to reduce the friction in the IP to help the whole differential pressure thing along)


Even so I think Kerry is right - a turbo charger would be the real solution to the problem.

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I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

The spring which I am thinking of removing a washer from under the base (acts like a shim which increases spring pressure) pushes the IP towards max load. The venturi vacuum fights this. While there would be lower pressure on both sides of the diaphragm, the spring is not affected by air pressure and so keeps delivering fuel as if the car is at sea level. With less density for the vacuum to pull and less density on the open side of the diaphragm to push, my theory is the spring pressure is overwhelming the pull of the diaphragm and so is creating the richer condition I have. I was just hoping one of the forum members might know if these spring shims are the item I need to attend to or if other adjustments should be made as well. In theory, there should be X number of meters in altitude which correspond to removal of y number of spring shims to better equalize the spring tension vs. venturi vacuum.

This is definitely happening tomorrow. I'm going to record the engine sound after warmup with the current number of shims under the spring then I'll do the same after I remove one or even two. I'll take it on a test drive and let the forum know what I come up with. I'm at 1/3 of a tank right now so I don't have enough fuel to do a mileage test. I'll start that after my next fill up.

Phil Forrest

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1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson

I warmed up the car and then recorded 20 seconds at idling on my audio recorder.
The idle has been a little high since I got up to this altitude, due to the lighter air not being able to pull as hard on the diaphragm. At this altitude, I've adjusted down the throttle body plate to lower the idle but it didn't come down much at all before this fix.

So I opened up the IP governor and took out two washers behind the spring.
After that, I put it back together and started it up. The idle was noticeably slower. I disconnected the the linkage rod to the IP governor while it was idling and then adjusted the throttle throttle body plate down and the idle finally dropped. I was able to almost stall the car with enough adjustment down, so I set the idle where it smoothed out, maybe about ~700 RPM.

I took the car on a hard drive on the freeway and there is noticeably less smoke. It still smokes when I get in the pedal and accellerate heavily, but there is no smoke when cruising. Yes, it has less power climbing hills but that is expected. It also accellerates slower if I go easy on the fuel to keep the smoke down.

I'm just about at the end of a tank of fuel so I'll start to measure fuel economy when I fill up and drive normally through the next tank. I think that if anything, the lower idle speed is going to reduce fuel consumption.

When I get the sound recordings downloaded and cleaned up, I'll post links to them.

Phil Forrest

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1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson

Keep in mind that retarded cam timing will reduce the engine's ability to pump air. Since a 240 at sea level normally runs with an almost invisible exhaust, that's where I would start.

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'83 300D, 126K miles.

I'm only here for another month so I don't want to do anything that drastic. Also, changing the spring tension spacers effectively allows the diaphragm to move like the air pressure is greater. Also, most 240s have ADAs on them so they automatically compensate for air pressure and will usually smoke much less than a pneumatically governed motor.

I don't want to pump less air, I want to pump more. I'm in agreement with the folks who say a turbo will do better but that's too much work for only a month more of high altitude.

Phil Forrest

__________________
1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson

I don't want to pump less air, I want to pump more.

I understand that; your retarded cam timing is giving you less air. Replacing the timing chain may restore the engine's volumetric efficiency to where it was when new.

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'83 300D, 126K miles.

I think the 220D only has a Pneumatic Governor.
If that is so I don't think any turbo that would boost over normal sea level atmospheric pressure would work.

I thought there was some adjustment on the Butterfly Valve or linkages that would compensate for the now excess Fuel.
Dose someone have the Manual for the 220D showing the Buttery fly linkages?

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84 300D, 82 Volvo 244Gl Diesel

I was thinking about this and since the pneumatic governor operates on ambient pressure there is no way to put a turbo on since it would not build vacuum in the venturi.

It all comes down to that way the spring pushes against the diaphragm and how to make the IP think the air pressure is greater. The only way to decrease the smoke and increase fuel efficiency now is by changing the spring out to one with a softer response. Problem is my acceleration will be awful so I will just deal with the way it runs right now and in a month will be heading back to sea level.

Phil Forrest

__________________
1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson

This may be a stupid thought but I have read and heard about a few members who have put a newer w123 240d injection pump on these older w115s.....they said it was a real easy conversation.....all that was needed was to add an oil feed line to lube the pump.....usually comment from the oil pan.....I never looked to far into this....but this would be an easy way to fix the altitude problem as then there would be an ada.....

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Yeah, an injector pump with the ADA is an idea but again, I'm only going to be here another month and I really want to keep the car as original as possible. One more month at 28mpg isn't bad. After this recent spring tension fix, the idle has dropped and the car is still very drivable so I think I will gain a little bit of efficiency.

Phil Forrest

__________________
1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson

Don't know if this was covered, but there is a diaphram in the exhaust system. I had the same problem on my 1976 220/240D. It was the last year they had the diaphram. When I sold my car to Pierre Hedary, he immediately went for that part, which he said was non-existent, as it was so eroded. I had been getting 30-33 mpg in high altitude but got a blast of black smoke out the tailpipe taking off from stop signs. After Pierre replaced the diaphram, the black smoke went away and fuel mileage went up to 36 mpg around Miami. Pierre also told me that because this part was hugely forgotten, most people tried everything and spent lots of money trying to fix the problem. Try this first, before messing with IP fixes, or otherwise other expensive repairs.

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1983 300D, the "Avocado"
1976 240D, 4-spd the "Pumpkin", SOLD to Pierre
1984 190D, 2.2L, 5-spd, my intro to MBZ diesels, crashed into in 2002

I wouldn't complain about 28 mpg. I usually get around 25 in the 300D.

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88 Jaguar XJS V12 94,xxx miles. Work in progress.

Do you know of a part number?

I don't have access to a pre-W123 FSM, and i can't find any reference to a diaphragm in the exhaust but I only started searching.

Yeah, I know but when I've gotten 35mpg out of this car, 28mpg is a big percentage loss.

Thanks!
Phil Forrest

__________________
1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson