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  #1  
Old 05-26-2013, 07:38 AM
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81 300SD won't shut down with key

This happened the other day when i went to pay for the car. The engine will not shut down with the key. All vacuum lines are fine.

I personally think it's the ignition switch itself.

This happened a few times randomly when i was going over the car, but then it would work fine.

Now it refuses to shut down with the key.

Electrically the car will shut down just fine.

Do the vacuum sections in the ignition switch go bad? Can said section just be sticky from sitting or from a lot of miles.

Would this be solved by changing the tumbler? The key does seem to stick a little. For example, when i turn it to start, it will go 1/2 way back to "run" then i have to turn it manually the rest of the way to get everything in the car to power on.

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  #2  
Old 05-26-2013, 09:57 AM
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The shutoff system works on Vacuum.
You are going to need to trouble shoot the System and a Hand Held Vacuum Tester generically know as a Mighty Vac (althoug Mighty Vac makes one) is helpful.

The problem can be caused by low Vacuum (you did not say you where having hard Braking issues).

The low vacuum can be caused buy a Vacuu leak of leaks anywere in your Vacuum System including your door locks and climate control.

What you need to do is disconnect and cap off (the end that supply the Vacuum) the Vacuum lines going through the fire Wall but leave the Brown Vacuum Lines connected.
That removes them from the System.

If you Engine shuts off normal whan that is done you have a leak in the Climate or your Locking System or if you have one the adjustable Seat (but you did not complain about these issues).

So we will focus on the Brown Vacuum Lines.
On mine the soild Brown Vacuum Line going through the Fire Wall is the Vacuum Supply line and goes to a Vacuum Switch on the Steering Colum Lock and the brown line with a dark blue (black?) strip goes fromt he Vacuum Switch to the Shutoff Vavle on the Fuel Injection Pump.

Start your Engine and disconnect the Brown Line with the Blue where it attaches to the Vacuum Shutoff Valve on the Fuel Injection Pump.
Connect a separate section of Vacuum Hose to the Vacuum Shutoff Valve on the Fuel Injection Pump and either suck on it or use the Hand Held Vacuum Tester to create Vacuum.
If that shutts off the Engine the Shutoff Valve on the Fuel Injection Pump is still good enough to work. However, if you found Engine Oil in the brown line with a strip the Shutoff Valve has some holes in it as it is leaking Oil.
Reconnect to the Shutoff Valve

Next disconnect the solid brown line going into the fire wall and do the same test with the Key in the off positionn. It should turn your Engine off. If not you have an issue with the other Vacuum Valve located on the Steering Colum or the Vacuum line or the rubber connections.

The pic is of the inside of the Steering Colum Lock and the Plastic Cam that operates the Vacuum Switch on it. I suppose it is possible for something to happen to that Cam but none our Members have had that Happen.

I had the center shaft break off but that effected the Ignition Switch not the Shut off Valve.
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81 300SD won't shut down with key-steering-colum-lock-vacuum-valvel-cam.jpg  
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  #3  
Old 05-26-2013, 10:39 AM
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Most likely cause is the vacuum shutoff valve. Test as described by diesel911 and then hollar at me if you need a good working used replacement shutoff valve.
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  #4  
Old 05-26-2013, 09:18 PM
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The 300SD only uses the vacuum pump for shutdown and climate control. The door locks have their own pump in the trunk that uses vacuum to pull the locks closed and pressure to push them back open.

I took the climate control out of the system, and it didn't make a difference. It still wouldn't shut down with the key.

It did this sometimes before when i was messing with the car, and i figured it was a fluke from it sitting so long.

It's gotten to the point where i think it's the key switch itself. I have to test with vac directly to the shutoff valve on the IP next time i'm at where the car is parked.

If it is the ignition switch itself, how hard are they to replace?

the key does seem to stick when turning, so i think the assembly is just plain worn out.

It does have 297,6xx miles on it.
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  #5  
Old 05-26-2013, 11:46 PM
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Quote:
Originally Posted by IamDave0887 View Post
The 300SD only uses the vacuum pump for shutdown and climate control. The door locks have their own pump in the trunk that uses vacuum to pull the locks closed and pressure to push them back open.

I took the climate control out of the system, and it didn't make a difference. It still wouldn't shut down with the key.

It did this sometimes before when i was messing with the car, and i figured it was a fluke from it sitting so long.

It's gotten to the point where i think it's the key switch itself. I have to test with vac directly to the shutoff valve on the IP next time i'm at where the car is parked.


If it is the ignition switch itself, how hard are they to replace?

the key does seem to stick when turning, so i think the assembly is just plain worn out.

It does have 297,6xx miles on it.
I have a differen year and mode. On mine when the Kick Panel is removed you can loo up under the Dash Board and you can see the Valve.

Itis very tight up there but I suppose someone could get in there and remove the 2 screws that hold the valve in place. I know I would have a tough time with that.
I was mainly taking the pic to show the Oil Leak but that is the Valve.

I read on another Forum wher someone had that Valve get plugged up.

No one so far has said they had a problem with the Plastic Cam that actuates that valve but that does not rule that out. The Cam is part of the Steering Colum Lock.
I just replace My Steering Colum Lock about 3 months ago. Most places sell the Steering Colum Lock as an assembly. You get the Steering Colum Lock, a new Ignition Switch and a new Vacuum Valve as an assembly.

But, it is best to do some trouble shooting before buying parts.

One person has had the ends of the Lock Tumbler worn. You would have to pull the Tumbler out to see that.
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81 300SD won't shut down with key-steering-colum-vacuum-valve-oil-leak.jpg  
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  #6  
Old 05-26-2013, 11:50 PM
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i will have to check and see if there is oil on the switch. that would indicate that the valve on the IP is bad correct?

How hard are those valves to change?

I plan on testing the vac switch part of the ign switch by hooking my vacuum gauge to the line that goes to the IP vac shut off and checking the gauge when the key is turned.

I'm thankful the 300SD is a seperate system for the door locks. that system seems to make more sense than the single vac system for everything. The single system becomes overly complicated, not to mention the whole not shutting down via the key scenario would be exponentially increased as the vac system grew in the car.
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  #7  
Old 05-27-2013, 12:09 AM
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Diesel911 gave great advice. I have dealt with this on both my 300D's. Usually the problem is either low vacuum (bad pump or leaks) or a bad shut-off valve on the IP, not the vac switch on the side of the key switch. It is easy to determine which component is bad w/ a hand vacuum pump and a vacuum gage, both cheap at Harbor Freight.

For the 2 tubes to the key vac switch, the polarity matters. It is analogous to a "single pole, double throw" electrical switch, if that helps. The tube to the shut-off valve is the "common" and the switch connects it to either "vent" or "vacuum". I didn't think of that and bought a new vac switch thinking that was the problem (they are fairly cheap). It wasn't easy to install, I ended up removing the switch stalk to access the screws (read up for the tricks to get that off).

Re your ignition switch being sticky, I had one like that. Search for my post. The spring-loaded detent ball failed inside, jamming it. I think that is common. Your tumbler part is probably fine.
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  #8  
Old 05-27-2013, 01:07 AM
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Hi Dave, (you da same guy from the DP forum?) welcome to My playground! it could be the flexible connectors that link the brown vacuum lines to the switch, or it could be the IP shutoff valve, or the vac valve in the ignition assembly itself. from your description, at a minimum you have an electrical problem in the ignition switch, as the spring that positions things after you start is in there. pullapart/pickandpull finds of any diesel after 82 will net you a good assembly, fairly simple to remove once you get access to the switch removing dash panels and such. if you pull an assembly from a vehicle newer than 89, you will have the ability to integrate the cable to lock the shifter with the key out, and require the brake to be pressed to move the shifter out of P... the key and tumbler can be ordered from any dealer matched to the vin of your vehicle.
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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Old 05-27-2013, 01:29 AM
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I found your thread on the GM forum...
good pics, repost them here please! and get some closeups of the engine IP area so we can see any issues you might have...

I'm copying my post from your other thread here.

from the pics the bumper rust is easy to fix with a replacement bumper, the vinyl seats will last a long time, but likely the springs supporting them have failed... pool noodles work well to firm them up, but your pics look like they are in good shape. the hole in the coin tray is likely from a replacement cigar lighter or accessory power socket attempt. I've got dozens of interiors if you want it back stock...
from all the pine needles under the wipers, I'd bet you have lots under the brake booster... get them all out of there, the blower speed resistor is under there, and is known to start a fire with leaves and such are in contact when the blower is on low speeds... you've got the wrong radiator reservoir cap on there, and the oil fill cap is from a v8 (it's slanted, not in line with the valve cover) also, I note you have 134 conversion caps on the a/c... Connecticut summers will likely survive on it, but if you drive in the south much that's a mistake!
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #10  
Old 05-28-2013, 08:24 AM
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I need to locate a replacement front bumper at some point.

What thread are the studs that hold the bumper on?

Mine are missing the nuts like someone planned to replace the front bumper and never finished. They look to be M12 sized jsut by eye-balling the stud size.

Also the master cylinder looks to be empty up front, yet full in back. When i went to fill it the back level went up, but the front level stayed low. I put my finger down the fill hole after topping it off and there's a plastic wall in between the front and rear chambers with what appears to be no way to fill the front chamber. What am i missing?


The A/C system probably doesn't work. The power connector for the compressor is hanging, unplugged.

The high side has a 134A fitting, the low side has an R12 fitting. Not sure what was being accomplished here, but it was never completed. I plan to put it back to R-12 as i have a bunch. I see it uses the GM R-4 compressor. those love to blown their front seal, so i have to see if it's any good before charging the system.

Sunroof doesn't work, not sure why. I hear no motor run, nor do i have any blown fuses when i use the switch.
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  #11  
Old 05-28-2013, 08:43 AM
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The brake fluid reservoir does have a wall between the front and back, but filling it up should overflow it.

My SD A/C compressor was seized up and when I turned it on, the belt ripped apart knocking the plug katty-whomppus.

The sunroof may be a bad switch, but pull all fuses in the fuse box and inspect the ends. I replace all of 'em when I get one of these cars.
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Last edited by toomany MBZ; 05-28-2013 at 08:46 AM. Reason: more info
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  #12  
Old 05-28-2013, 06:46 PM
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Quote:
Originally Posted by toomany MBZ View Post
The brake fluid reservoir does have a wall between the front and back, but filling it up should overflow it.

My SD A/C compressor was seized up and when I turned it on, the belt ripped apart knocking the plug katty-whomppus.

The sunroof may be a bad switch, but pull all fuses in the fuse box and inspect the ends. I replace all of 'em when I get one of these cars.
I read about changing all the fuses, and have already done this. It seems to fix a few things, but others remained the same.

At some point i plan to pull the sunroof switch out and jump it to see if it works that way.

The drive belt on the compressor is stupid loose right now, just basically sitting on the pulleys and flopping about. The plug seems to be intact, just filthy. I have to get a closer look at it.

The R4 compressor was a POS basically. it's a GM/Harrison unit that loves to blow it's front seal, leak all the refrigerant and oil out and lock up.

Wish i could fit an A6 in there instead. I'd be blowing ice cubes out of the vents then.

The rear of the reservoir appears to be full, but i may try adding more to see if it overflows into the front section.

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