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Old 01-31-2008, 09:33 AM
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Join Date: Mar 2006
Posts: 8
300D engine will not stop

The engine in my 1985 300D won't stop after I turn off the car and remove the key. I've had to raise the hood each time and push the kill switch. I've only had the car for a few weeks, so I don't know it very well.

My Haynes manual gives me no help as to how to solve this problem. Is it something in the vaccuum system?

Thanks a lot!


"not stopping is better than not starting."

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Old 01-31-2008, 09:36 AM
thesst's Avatar
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Location: Ellensburg, WA
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Yeah it's the vacuum system. Big leak somewhere.
'79 300SD
'82 Chevy Chevette diesel
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Old 01-31-2008, 09:37 AM
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Location: Redmond, WA
Posts: 622
Yes, it's something in the vacuum system.

Prime candidates include power door locks and climate control servos (you probably have automatic climate control.)

Cap off first, one, the other, than both and see if the problem changes at all. For me, it was power locks -- capping off that part of the vacuum system fixed it totally.
1983 Mercedes-Benz 240D
Automatic, A/C, Power Sunroof, Power Right Side Mirror
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Old 01-31-2008, 09:37 AM
TX76513's Avatar
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Join Date: Apr 2003
Location: Brandon, Mississippi
Posts: 5,203
Yes probably vacuum related.
- Leak in system that is not allowing enough vacuum to engage shut off valve
-Shut off valve is broken
-Vacuum valve on ignition switch is broken/leaking

Do you have a Miti-Vac or similar device?
15 VW Passat TDI
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98 E300 DT
97 E420 Donor Car - NEED PARTS? PM ME!
97 S500
97 E300D
86 Holden Jackaroo Turbo D
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Old 01-31-2008, 09:38 AM
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Join Date: Oct 2005
Location: Tennessee
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You're not the first to have this problem and you won't be the last!

There is a brown vacuum line that runs from the drives front wheel well to the shut off valve on the back of the injector pump. Follow that line and make sure the hoses are pushed up in the rubber fittings.

90% of the time that is the issue. It happened to me when I was changing the clear primary filter down by the lift pump. It is easy to do.

BTW, use the search feature, this problem is VERY well documented here on the forum. There are even some nice photos out there.

1995 S350D, Green with black leather interior.
Bought January 2008 w/ 233,xxx miles.
I did 22,000 miles during the first year of ownership.
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Old 01-31-2008, 09:42 AM
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Location: Arlington, VA
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There are great vacuum diagrams at the top of the General Information section. They will probably be helpful to you.
" The market, like the Lord, helps those who help themselves. But, unlike the Lord, the market does not forgive those who know not what they do."- Warren Buffett

OBK #55

1998 Lincoln Continental - Sold
Max 1984 300TD 285,000 miles - Sold
The Dee8gonator 1987 560SEC 196,000 miles - Sold
Orgasmatron - 2006 CLS500 90,000 miles
2002 C320 Wagon 122,000 miles
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Old 01-31-2008, 09:53 AM
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You'll need to trace down the vacuum problem but it is usually not the shut off valve itself that is the problem. In the meantime, buy a 4' length of rubber vacuum hose of suitable diameter. Follow the brown vacuum line described above. Remove the brown vacuum line from the shut off valve and replace with the vacuum hose. With the engine running, suck on the hose. If the engine shuts off, you have confirmed your shut off valve is ok. Run the hose out of the engine compartment at the cowling, leaving about a foot exposed. Now shut the hood. Until you trace down the vacuum leak, you can how shut off your engine without opening the hood by simply sucking on the hose.
Tolerate this solution either until you have learned enough about the vacuum system to isolate the problem or you get too embarassed to do it anymore.
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 01-31-2008, 10:15 AM
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OK. Right by the brake booster you will see vac lines going through the firewall.
Yellow is door locks.
Yellow/gray is vac. cannister in trunk
Green is climate control stuff
Brown is shutoff to key switch
Black is a vent line to under dash area

Golf tees or similar is useful here.
Unplug green line and put tee in rubber connector to block it. Start car, let run for 30 seconds and try and turn off.
Next, if it still runs, unplug yellow line, plug up connector and do the same.
These are the two most common.
The above assumes you do not yet have a Mityvac, which you should be purchasing shortly {around $30-35 bucks}
Also, this assumes you followed the large vac tube from vac pump at front of engine to make sure there was not broken tab off of it, or any unplugged vac line.
Since you didn't mention you had very hard brakes we'll assume the vac pump is working. And it isn't usually the shutoff valve.
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John
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Old 01-31-2008, 10:31 AM
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Location: Roswell, Georgia
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here is a link to the thread that I just went through with all these guys...and they helped me might want to just read through the questions that came up for me and some of the extremely helpful tips from the many responses I had...

1991 300CE Sportline
1983 300SD TurboDiesel (Gone but not forgotten)
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