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  #1  
Old 12-12-2007, 12:41 PM
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W123 300D won't shut off--vacuum leak? HELP!

I need a bit of quick help here. I am bidding on an '84 300D non-turbo stick. It apparently starts and runs fine but will not shut off. The interim method is to stall it. Owner says this is due to a vacuum leak.
Does this sound right? I just want to be sure it can't be a defective fuel pump ($$$).
I have to decide what to do in the next few hours so any help would be much appreciated!
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  #2  
Old 12-12-2007, 12:54 PM
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This problem has been addressed a number of times on this forum but I am not computer savvy enough to direct you to the postings. In a nutshell a vacuum soleniod is employed when the ignition switch is turned off and the solenoid blocks the flow of fuel. A quick way to shut the engine off it to manually push the lever (that says 'STOP) by the injector pump. In pushing the lever, your hand is providing the power that should be provided by the vacuum. Repairing this problem is not too difficult and is explained in depth in those postings I spoke of. Good luck
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  #3  
Old 12-12-2007, 01:11 PM
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Almost certainly a minor problem. Could be a leak, disconnected line, bad shut off diaphragm or bad vacuum pump. Non of these are serious problems especially if you have any shade tree mechanic experience.
These kinds of problems are godsends when when purchasing an MB diesel because they keep the buying pool small. It does say something about the mechanical ability and marketing intelligence of the seller.
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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
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Old 12-12-2007, 01:18 PM
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agreed

this isn't (well, probably not) a costly fix...and Kerry is right, chances are.....the seller has inadvertantly whittled away all the bidders foolish enough to dramatically inflate the car's worth.....so the few remaining that know and understand MB's probably won't bid too much.

Even if you're not mechanically inclined, presuming that you can read and search this forum - you'll be fine.

Good luck
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Old 12-12-2007, 01:25 PM
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Ok, thanks. I am feeling much better about this. I'm not much of a mechanic but can follow directions and part of the reason I am interested in a W123 is the famed ease of working on them. So long as I've got another car to get to work in in case I screw up I'm not afraid to dig in.

Question: While I'm working on the vacuum system is there any chance of putting the car into a runaway state as discussed here (skip halfway down the page to get to the Mercedes part
http://www.motorwatch.com/automotivebible/mechanics_nightmares/mnmDiesel.htm
Quote:
You're probably wondering why MBZ diesels run away. First, they rarely throw off their flywheels and seldom explode. But, it can happen in one of two ways. The first is when the throttle linkage sticks. This isn't much of a problem as long as you keep the ball-sockets properly lubricated. MBZ fits the engine with a shut-down lever that looks like a choke knob. Also, located right above the injection pump, is a manual fuel cut-off device. But, modem MBZ diesel engines use a shutdown system that's operated by the ignition key. A small vacuum motor mounted on the rear of the injection pump performs the shut down.

The second way is when the vacuum motor diaphragm ruptures. The owner find that the only way to shut down the engine is to get out, open the hood, and press the manual shut down lever. Not the sort of thing that MBZ owners could be likely to do, huh? Well, the replacement of the vacuum motor can be tricky. It has a small tang on it that must catch in a notch on the injection pump rack. If it doesn't, it'll jamb the rack in a wide-open-throttle position and bingo, "Runaway Diesel."
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Old 12-12-2007, 01:37 PM
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Yes, replacing a vacuum shut off diaphragm incorrectly can cause the engine to runaway. It is a simple problem to avoid. All you need is a readily available method of stopping the engine should you make the mistake.
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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
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Old 12-12-2007, 01:42 PM
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welcome to forum

Quote:
Originally Posted by herring View Post
Ok, thanks. I am feeling much better about this. I'm not much of a mechanic but can follow directions and part of the reason I am interested in a W123 is the famed ease of working on them. So long as I've got another car to get to work in in case I screw up I'm not afraid to dig in.
seriously, you've come to right place.....as for having another car in case something goes wrong? Well, I can't help you there....for I'm but a foolish boy.

bad morning

See post 32
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Old 12-12-2007, 01:57 PM
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My three experiences were always door lock actuators. A quick way to test this is to start the car shut it off (assuming that it will not) and then lock the doors. If it then shuts off (slowly) then you likey have a bad door lock line or actuator.
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  #9  
Old 12-12-2007, 03:04 PM
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I like the transmission, but I think all imports to the US from '82 on were turbos, and NO sticks. It wouldn't surprise me it's a gray market car, makes ordering parts an adventure!
Yes, there is a vacuum leak somewhere, and no that will not cause a runaway.
Try pulling vacuum with a device, mity-vac, or something similar to see if the shut off valve itself works. The brown with purple stripe vac line under my hand goes to the shut off valve, with the car running, pull vacuum, if the car shuts off, the valve is good.
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Old 12-12-2007, 05:02 PM
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Quote:
Originally Posted by toomany MBZ View Post
I like the transmission, but I think all imports to the US from '82 on were turbos, and NO sticks. It wouldn't surprise me it's a gray market car, makes ordering parts an adventure!
Yes, gray-market import. Originally sold in Germany. Unfortunately, it's over $3,600 now. Not sure at what point it becomes 'not worth it' on a car I've never seen.
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Old 12-12-2007, 10:10 PM
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Quote:
Originally Posted by herring View Post
Yes, gray-market import. Originally sold in Germany. Unfortunately, it's over $3,600 now. Not sure at what point it becomes 'not worth it' on a car I've never seen.
That's going to be a personal decision, yet depending on how many miles, and what climate control system it has, if a manual set up, manual sun roof too, that is a desirable car, watch the price go up. I paid $10,000 for the CD a few years ago, with 83k on the clock.
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Old 12-12-2007, 10:10 PM
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