I just bought a 1983 240D. It ran great until last Friday. I had a little difficulty turning the ignition but finally got engine turned on. Then when I turned it off the motor kept running, even after the key was out. It was difficult to turn off even with the stop mechanism under the hood. I have only had the car a couple weeks. The owner said it ran fine and I actually drove it a week before buying it. It ran great up until Friday. HELP! I am afraid to drive it (I actually won't drive it until fixed.)My husband has checked the hoses and they seem to be fine. Any suggestions on where to go next?Is this a common problem with diesels?

Don't panic. It is most likely a simple vacuum leak. Simple in terms of expense, but can be a bear to locate. Try following the lines to/from the vacuum control module. I'm not sure where it is on a W123, but you will see several vacuum lines going to/from it.

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Chris

'04 ML500 - 53k, Inspiration Edition, Desert Silver
'11 Audi A4 Avant - Brilliant Black
'87 300SDL sold
'99 C280 Sport sold
'85 190E 2.3 sold

My car did this and I had to replace a diaphragm valve thing on the side of the injection pump. To check it you take off the plastic line that leads to it and see if there is any oil in it. This is a fairly common problem and a little tricky to fix. You must be SURE the new one is "engaged" or you cause some kind of catastrophic "can't shut it off" problem. Lots of Luck

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When I close my eyes, and inhale, I can smell No. 2.

You stated that you "had a little difficulty turning the ignition but finally got engine turned on". Did you mean that the engine was hard start or that you had difficulty turning the key? If the problem was the key in the ignition switch, then this could also be the cause of shut off problems. The ignition switch on our 240d is pretty worn. If my wife isn't careful about how she puts the key in, the ignition switch is difficult to turn on AND the car sometimes won't shut off unless she puts the key back in correctly, and turn the switch off again. There's a small vacuum switch on the back of the ignition houusing (that controls the the shut-off on the fuel pump)that's not releasing if she's not careful with the key.
Do you have vacumm going to other items on the car (door locks, brakes, auto trans)???

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1980 Mercedes 240D
1982 Mercedes 300SD
1985 Mercedes 300D
1993 Dodge Cummins Turbo Diesel

Where is the ignition housing on the 83 240D? Is it difficult to get to?

Greetings Susieq,

You are experiencing one of three posssible problems trying to shut off your engine. The first is the ignition switch, or for us diesel addicts it's a vacuum operated switch for the engine to pull the fuel rack back to the no fuel position. Does the key switch operate smoothly in all positions? With the key turned to the off position, does it provide vacuum to the shut off valve? The shut off valve is the second area where the problem might exist. It is located on the rear of you injection pump and will have a vacuum line going to the top end of it. If there is no vacuum line connected to the top, then you have reached the third problem area, and also the easiest to fix. There should be a vacuum line connected to the rear of this shut off valve. If there isn't, it's tangling in your engine compartment and needs to be put back onto it's connection on the valve. Check the line out first, then tell me about your key switch condition.


Charles

I have an 82 240D that will not shut off with
the key now too. I just replaced the steering
lock and ignition tumbler and also the
"switch over" valves under the black box on top
of the valve cover. Now, this no shut off
problem starts. I've checked the vacuum lines
and don't "see" anything obvious. I replaced
the brown line to the upper (outer) connection
on the steering lock and the brown with blue
line to the lower (inner) connection. I also
replaced the vacuum lines with the switch
over valves.

When I drive the car for a short distance,
the key WILL shut off the engine. If I start
and stop it in my driveway after a drive, it
will shut off about 2 times before not shutting
off again.

Seems like a vacuum leak, but where?!

Is the vacuum pump diaphragm a separately
replaceable item?

Maybe it's time to get a vacuum gauge and
hand pump? Does Sears carry them?

Any advice or suggestions welcomed.
I need a vacuum troubleshooting guide for
beginners.

- Jeff

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- Jeff

1957 W121 190 (history)
1966 W108 250S
1967 W108 250S (parts)
1982 W123 240D (history)
1989 W124 260E

There are always new ways for things as complex as the control system for a 240D to fail, but the most likely ones are the first places to look.

I have never had the ignition switch fail to operate the vacuum valve to shut the engine off, but I have had the diaphragm in the shut off mechanism fail, and allow oil to leak into the switch. This caused the vacuum line rubber end fitting to swell and the line fell off, spewing oil under the dash and down the driver's side of the console about where my knee touches it. A mess and the car would not shut off.

I have also had the vacuum line to the shut off mechanism come off, most likely while I was either changing the oil filter, or doing some other poking around in the area. That was easy to fix. And I have had the little vacuum check valves fail, as well as the door lock mechanisms, all of which conspire to make the vacuum storage features useless, and once again the car would not shut off.

So, if your door locks work, you probably do not have gross vacuum leakage that disables the system. The problem is more likely limited to the vacuum circuit that controls the shut off valve. In that case, I would inspect the lines and connections in the engine compartment, on the driver's side of the engine to see if any lines are disconnected, or the fittings at the ends are swollen, cracked or loose. I would also pull the line from the fuel shut-off mechanism on the rear, top of the injection pump to see if there is oil on the inside. If there is oil there it is leaking through a ruptured diaphragm in the shut-off mechanism and you will probably need a to install a new mechanism and clean out the lines to and from the ignition switch. If there is no oil, the mechanism is probably ok.

Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Here is a test of the vacuum diaphram that shuts off the fuel. Find the brown vacuum line that goes to the rear of the Injection pump (IP). Pull it off and put on another vacuum line long enough too reach your mouth. Suck on this line when the engine is running and if the engine shuts off, the shutoff parts in the IP are OK and the problem is something else.
Get a vacuum gage and see if there is vacuum in the brown line you removed earlier with the key off. There probably won't be any vacuum there so next check one of the lines near the vacuum pump. If vacuum is OK near the pump, then you will have to trace the lines to and from the the Key switch (Diesels` do not have an ignition switch).

P E H

Just to make sure:
Where is the shut off valve?
Is this the white plastic contraption
on the top-rear of the injection pump?



This car is new to me and I don't know what
I'm looking at yet. w123 CD-ROM "in the mail".

So the diaphragm is a R+R piece on the shut off
valve but maybe not on the main pump.

Thanks for the correction on the "ignition switch"
term. Should have known it wasn't called that.

Jeff

In the picture I see a brown vacuum line. I think this is the shut off line. The off white thing in the picture is the vacuun valve. It controls the vacuum to the transmission. If you take the vacuum lines off the vacuum valve, make sure you replace them the same way or you can ruin the transmission like I did. ~~~~P E H~~~~

You can't ruin the transmission by leaving the vacuum line off. it will only shift hard.

If your manual stop (red) lever barely shuts it off, the lever itself can be adjusted easily. I had to do this with mine as a first step before looking for all the vacuum leaks. Once I adjusted it, the manual stop lever shut down the car immediately.

Don

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DAILY DRIVERS:
'84 300DT 298k (Aubrey's)
'99.5 Jetta TDI IV 251k (Julie's)
'97 Jetta TDI 127k (Amber's)
'97 Jetta TDI 186k (Matt's)
'96 Passat TDI 237k (Don's
'84 300D 211k Mint (Arne- Undergoing Greasecar Conversion)

SOLD:
'82 240D 229k (Matt's - Converted-300DT w/ 4 speed

Maybe leaving the vacuumline off won't ruin the transmission, but if that 3 way connector is put back so that the trans gets full vacuum all the time, The transmission will start to slip and will have to be rebuilt. It may take thousands of miles to start to slip, but eventually it will. ~~~~P E H~~~~

I found the problem. I had replaced the vacuum
line that runs from the vacuum pump to the
brake booster. The rigid line with the
valve in the middle. Having tracked down all
kinds of vacuum lines all day with no luck,
I decided to put the old line back in (from the
pump to the booster). Engine stops again with
the key.

Only problem now is that I'm back to my funky
shifts (automatic). Shifts too soon and
flares between gears.

What is the "problem" with the new vacuum line?

Can I adjust something so that I can use the
new vacuum line and get the great shifts but
also get the engine to turn off with the key?

- Jeff