My 79 300 sd is not shutting off with the key lately. It wouldn't even shut off today with the "stop" lever under the hood. Ended up pulling the fuel line at the inline filter and running it out of fuel~
According to the Haynes manual, there is a fault in the fuel system cut off solenoid, Now if they would only show me where it is!!
Can someone please tell me what the heck I am looking for!?

The shut valve is on the back of the injection pump. It a round thing about maybe an inch and a quarter in diameter. It has a vacuum line going to it. You'll need a mity vac to test it. You hook the mity vac up the the valve, start the car then give the mity vac a couple pumps and it should shut the car down. If it doesn't then you need to replace the shut off valve.

The stop lever should shut the car down no matter what. I would suspect that the linkages need adjustment, and that when you press the stop lever its not fully actuating, which won't shut the car off.

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Insid the Red Square is the Fuel Injection Pump Vacuum shutoff and the Lavender Arrow point to where the Vacuum Hose connects to it.

If you do not have a Mighty Vac you can remove the Brown Vacuum Tubing and the short Hose on the end and connect up a length of Vacuum Hose and simply suck on it. If if the Engine shuts off you are OK with the exception that if when you pull off the origional Vacuum Hose/Tubing there is Engine Oil there. If so you have a hole in your IP Vacuum Shutoff and it will need to be replaced.

More often the shutoff does not work due to a Vacuum leak In the other areas. Like the Door Locks, the Climate Control, those little white valves up on the Valve cover that operate the EGR and of course a Weak Vacuum Pump (are you haveing any hard braking issues).

If all of the above stuff is OK that pretty much leaves the other Vacuum Shutoff Valve located on the Steering Wheel Lock Housing. The Valve or the Hoses/Tubings that connect to it could be leaking.
Some of the issues are covered here:
vacuum issue

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84 300D, 82 Volvo 244Gl Diesel

The manual idle control knob may be turned up high enough to hinder full travel of the stop lever linkage. You can test the shut off valve without starting the engine by pulling a vacuum on it. It should hold vacuum. If it doesn't and if you suck oil, it's bad. But failure to turn off is most often an indication of a vacuum leak somewhere else in the system.

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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

Spent the last couple of weeks looking for our mightyvac, have decided that it has gone AWOL.
Went and got one at the parts store, pulled the brown vac. line, pumped the vac. tested and nothing~ no change in idle, no stop, nothing.
Pulled the other 2 lines on the unit (see photo) same nothingness!
Have tried to adjust the idle, but could not get enough "distance" to make a noticable difference on the linkage that runs horizontal and is connected to the "stop" lever. (sigh)
There was no oil in any of the Vac. lines.
Finally just pulled the fuel line again and ran it out of fuel.

If I am reading the post of Biodiesel300TD, this means I need to replace the shut off valve, right?

p.s. no braking issued,but the door locks don't work! Guess that 's next, but not as pressing!

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This may sound odd, but which end did you pull the vacuum on? Vacuum needs to be pulled on the shut off valve which is down between the IP and oil filter housing. Did you remove the brown vacuum line and then connect the mity vac to the fitting on the back of the IP. No real need to have waited for the mity vac. You can just suck with your mouth and shut if off. If that shut off valve is not holding vacuum, it should be leaking oil into the mity vac or your mouth.
The other lines going to the plastic fitting on top of the IP are vacuum lines going to the vacuum control valve (VCV) which is the plastic device on top of the IP.

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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

I am confused also. He needs to disconnect the Brown Hose shown in his pic and connect a separate Hose from the Mighty Vac down to that actual Shut off Valve/Solenoid. Down below the where the Brown Hose connects; see the yellow arrow.

Ounce connected start pumping on the Mighty Vac and see if it shuts down the Engine.

It also would have been nice for Him to have used the Mighty Vac and see how much Vacuum your Vacuum Pump is putting out.

I added a pic, the Red Arrow points to the spot where the Vacuum Hose from the Mighty Vac to the shut off should go. I this case there is a Rubbe Elbow on it already.

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84 300D, 82 Volvo 244Gl Diesel

Guess I had it in my head that I put it on the vac. line.
Next time I fire up the car I will try to shut it off by putting the mightyvac on the shut off valve~
Thanks for setting me straight on that, will let you know how it all turns out!

Finally had the time to fire up the car knowing that it might take a while to shut it back down.
Yes, when I put the mighty vac into the back of the IP valve and give it a couple of squeezes it shuts rights down. (this means the shut off valve is bad, right?)

No it means the opposite. The shut off valve is fine. It's not shutting down because it's not getting vacuum for some reason. You'll need to trace down the source of the low vacuum.

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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

Perfect timing on this thread. I just replaced all the belts on my 85 300SD and after starting and running it same thing ---- would not shut off except manually.
I looked around any where that I had to get in upto my elbow in and found the small brown vac line disconnected. I pushed it back in and now all is right with
the world.
Alan

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92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )

you have a vacume valve that is atached to your ingnition switch that sends vacume to the cut off switch at the pump , sounds like eather the vacume line is off or it is bad.