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  #1  
Old 11-16-2004, 04:10 PM
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my shut off problem (W126)

I have done numerous searches and reads on this wonderfull forum on the famed diesel engine shut off woes. My 1984 300SD is/was not shuting down when I removed the key. I have the a new vacuum shut off valve but do not want to install it until I am sure that is the cause.

Automatic door locks work, heat works.

Pulled a mity vac directly to the shut off valve next to the IP and it shuts the engine off.

I have cleaned vacuum conectors, tee pee conector, vacuum lines looking for leaks. Not much improvement. Pulled instrument cluster and the ignition key shut off valve and vacuum lines have black oil on it-semi cleaned. Not much improvement.

Tightened the nuts on the big lines with a 19mm wrench going from the IP and now the engine shuts off, but not perfect.

Questions-Do i need to remove/complete clean or replace the ignition key shut off valve? Do I need to replace the vacuum shut off valve next to the IP? Where is this black oil on the key shut off valve comming from? brake booster? worn diaphram in the vacuum shut off valve? There is no oil in the line comming from the shut off valve to the control valve.

Thanks for the help

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1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

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  #2  
Old 11-16-2004, 04:14 PM
boneheaddoctor's Avatar
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Quote:
Originally Posted by James L
I have done numerous searches and reads on this wonderfull forum on the famed diesel engine shut off woes. My 1984 300SD is/was not shuting down when I removed the key. I have the a new vacuum shut off valve but do not want to install it until I am sure that is the cause.

Automatic door locks work, heat works.

Pulled a mity vac directly to the shut off valve next to the IP and it shuts the engine off.

I have cleaned vacuum conectors, tee pee conector, vacuum lines looking for leaks. Not much improvement. Pulled instrument cluster and the ignition key shut off valve and vacuum lines have black oil on it-semi cleaned. Not much improvement.

Tightened the nuts on the big lines with a 19mm wrench going from the IP and now the engine shuts off, but not perfect.

Questions-Do i need to remove/complete clean or replace the ignition key shut off valve? Do I need to replace the vacuum shut off valve next to the IP? Where is this black oil on the key shut off valve comming from? brake booster? worn diaphram in the vacuum shut off valve? There is no oil in the line comming from the shut off valve to the control valve.

Thanks for the help
Oil in the vacume lines is a sign your vacume pump is in dire need of a rebuild.

Or that it was at some point in its life, and the lines were not cleaned afterwards.
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1983 300D W123
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1989 Honda Civic (Heavily modified)
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  #3  
Old 11-16-2004, 04:23 PM
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Please nooooooooooo boneheadoc!!! not the vacuum pump! The expensive thing on the front of the engine? Why is oil not in any other vacuum lines except the two near the steering lock? Could it be a bad diaphram in the shut off valve next to the injection pump letting oil/fuel through?
__________________
1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

609 Certification
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  #4  
Old 11-16-2004, 04:29 PM
boneheaddoctor's Avatar
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Quote:
Originally Posted by James L
Please nooooooooooo boneheadoc!!! not the vacuum pump! The expensive thing on the front of the engine? Why is oil not in any other vacuum lines except the two near the steering lock? Could it be a bad diaphram in the shut off valve next to the injection pump letting oil/fuel through?
since door locks and stuff works I doubt the pump is bad. Thats how oil usually makes its way into the vacume lines. it could have been that for 5 years for all you know. I don't know if the shutoff valve could do it. Never had one off. But Its not beyond the realm of possibility I guess.
__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche
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  #5  
Old 11-16-2004, 05:14 PM
Rick Miley's Avatar
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Oil in the key switch doesn't come from a faulty vacuum pump, it comes from a faulty shutoff device. The diaphram rips and the vacuum system sucks in oil from the injection pump. If the line from the shutoff to the key switch is clear, then it happened sometime in the past and the shutoff device was replaced.

The problem is that the oil ruins the rubber connectors and rubber parts inside the key switch. If you're lucky, it's just a connector. If not, then you'll need to replace that portion of the key switch.

BTW, your door locks are run from a separate vacuum pump (electric) in the trunk.
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  #6  
Old 11-16-2004, 07:48 PM
boneheaddoctor's Avatar
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Quote:
Originally Posted by Rick Miley
Oil in the key switch doesn't come from a faulty vacuum pump, it comes from a faulty shutoff device. The diaphram rips and the vacuum system sucks in oil from the injection pump. If the line from the shutoff to the key switch is clear, then it happened sometime in the past and the shutoff device was replaced.

The problem is that the oil ruins the rubber connectors and rubber parts inside the key switch. If you're lucky, it's just a connector. If not, then you'll need to replace that portion of the key switch.

BTW, your door locks are run from a separate vacuum pump (electric) in the trunk.
I didn't know the 126 chassis had the electric pump for the doors.THe W116 is the only model I know well.
__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche
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  #7  
Old 11-16-2004, 10:37 PM
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I agree with rick. My 85 300SD has a vacuum pump in the trunk. I don't know how reliable this is, but those Key lock really take a beat'n so I would not discard another suspect just yet. I was having problem with my car not shutting off. I looked at the vaccum pump, I removed the ignition vacuum diaphram....Nothing. Guess what...three rubber diaphrams that control the flaps for a/c ducts were busted. Well, as soon as I replaced them, the car started shutting off immediatley, Plus, my tranny started shiftting smoother. Better take a look around to see if one of your diaphrams is busted!!! If you are having problems with a/c controls and air directed in the wrong way...BINGO!
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  #8  
Old 11-17-2004, 12:39 AM
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Location: Evansville, Indiana
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I believe the shutoff line is brown with a blue stripe, supply is plain brown. You need to check ALL the vac lines and connetors in the engine compartment, they are all getting pretty hard by now.

Other things that leak will cause the vac supply to be low, so what I would do is hook up the mitivac to the shutoff line and pull the key. You must get decent vac there. If you don't, pull off the supply line somewhere in the engine compartment and see if you have vac on the supply side (should be 11" at least). If not, check the fitting for cracks or crap clogging the hole in the main vac line fitting.

Oil in the keyswitch means someone has already replaced the servo. See if it holds vac with the mitiVac (pump down and watch the gauge -- if it doesn't drop off, the servo is fine). Next, with key out, reconnect the vac line to the servo and pump down the brown line. If it won't hold vac, and the rubber connectors are OK, the keyswitch has been ruined by the oil.

Check to make sure the hoses are on the switch are on corretly,, too -- if they are backwards, it leaks.

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #9  
Old 11-17-2004, 09:17 AM
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Location: Greenville, NC
Posts: 533
Insightfull replys all! thanks! Engine is now shutting off, but it takes about 2 seconds. As stated the vac pump mainline 19mm nut was loose.

I am now hearing a periodic flap closing under my drivers dash speaker area. (even when climate control off) Did I disconnect something when pulling instrument cluster?

The lines may be backwards on the back of the key shut off valve! One is blue/brown and one is brown. Does any one know the correct orientation?
Not much room for my hands through the instrument cluster hole or from underneath. Do I need to drop the steering column, remove key cylinder,
or steering lock to access and swap lines-clean/replace? (I would rather not).
__________________
1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

609 Certification
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  #10  
Old 11-17-2004, 09:37 AM
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Try swapping them in the engine bay and see if it works any better. Much easier access there.
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  #11  
Old 11-24-2004, 06:10 PM
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Very interesting thread.

Can someone tell me the exact location of the vacuum shut off valve?

Thanks

Danny
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  #12  
Old 11-28-2004, 12:50 PM
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Danny:

I believe the shutoff servo is on the rear of the IP on that model. Will have a brown plastic line with a blue stripe connected to a nipple on a metal "can" held down by two or three bolts.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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