240D shutoff valve on the ignition lock.

[pj67coll]

My car wont shut off with the key and I believe based on the troubleshooting I've been doing with the Mityvac that the issue is the vacuum gizmo on the ignition switch. Am I going to have to pull the dash and then the ignition lock to get to this or can it be reached from below? Anybody ever have to replace one of these gadgets?

- Peter.

[Sugar Bear]

No dash removal, remove lock cylinder, then steering lock assembly with ignition switch. Not that bad to do. You might but I'm not sure, be able to remove just the valve with everything in place but I've never tried it.

Good luck!!!

[Diesel911]

The shut off valve is in the pic. It is held in with 2 screws. In theory if you mange to remove the 2 screws you can exchange the valve for a new one. However, it is extremely cramped in there.

However, If you did get it off you could replace the screws with Allen head screws which I believe would make it easier to tighten when you put in the new one.

Another however, is that the cam part that actuates the shutoff valve is made of plastic and after 25+ years it could have deteriorated. So it is likely better to remove the Steering Colum Lock and inspect it.

The lower right item is approximately the position the lock is in when it is mounted.

[pj67coll]

When you say steering column lock. Do you mean that entire contraption in the picture?

- Peter.

[BillGrissom]

Not sure which car you are talking about. In my W123, I can easily remove the vacuum switch by itself. You must remove the under-dash cover (how many times have I done that?). I might have used a phillips insert in 1/4" socket wrench due to limited clearance.

Before doing all that, you can test the vacuum switch. It would be easy to swap the 2 brown tubes going to it, in which case it wouldn't work. It is a SPDT switch. The tube from the shutdown valve should go to the "pole". The vacuum source should go to the "terminal" which is active with key switch in OFF. The other "terminal" should be open to the air (can't see it) and active when key switch is in RUN and CRANK.

[pj67coll]

Originally Posted by BillGrissom

Not sure which car you are talking about. In my W123, I can easily remove the vacuum switch by itself. You must remove the under-dash cover (how many times have I done that?). I might have used a phillips insert in 1/4" socket wrench due to limited clearance.

Before doing all that, you can test the vacuum switch. It would be easy to swap the 2 brown tubes going to it, in which case it wouldn't work. It is a SPDT switch. The tube from the shutdown valve should go to the "pole". The vacuum source should go to the "terminal" which is active with key switch in OFF. The other "terminal" should be open to the air (can't see it) and active when key switch is in RUN and CRANK.

It's my 81 240D I'm talking about. I suspect a problem in the internals of the contraption because when I switch off I get a slight attempt at an engine slowdown, as if the system is trying to shut off but thinking, nah, can't be bothered. If it push and twist hard on the key (not hard enough to break it etc...) it seems to have slightly more effect, but nowhere near enough to switch off. Which seems to indicate some internal issue rather than a compromised vacuum line.

I shall attempt to get in there from under the dash and see what can be done before resorting to screwing around with the whole instrument cluster and ignition lock removal.

- Peter.

[Diseasel300]

Have you checked the shutdown diaphragm before blaming the key switch? Get a mityvac and see if you can pull and hold vacuum on it (it should hold vacuum indefinitely). The vacuum "switch" is usually not the problem, it's generally a degraded vacuum line or a failed vacuum element in the shutdown pod.

You also haven't mentioned what the vacuum is on the supply side of the key switch. If it's low, or if the vacuum in the system is low in general, you can expect problems. You could have vacuum pump issues, leaking lock system, leaking brake booster, failed check valves, rotten rubber connections, etc.

[pj67coll]

Originally Posted by Diseasel300

Have you checked the shutdown diaphragm before blaming the key switch? Get a mityvac and see if you can pull and hold vacuum on it (it should hold vacuum indefinitely). The vacuum "switch" is usually not the problem, it's generally a degraded vacuum line or a failed vacuum element in the shutdown pod.

You also haven't mentioned what the vacuum is on the supply side of the key switch. If it's low, or if the vacuum in the system is low in general, you can expect problems. You could have vacuum pump issues, leaking lock system, leaking brake booster, failed check valves, rotten rubber connections, etc.

I've already used the mityvac to test. I get 23.5 Hg with the engine Idling when connected directly to the large black line from the pump (Which was rebuilt a few years before I got the car). Brakes seem fine, with good bite and no sign of having to press the pedal unusually hard to stop.

Door locks are buggered but were from before I got the car. Had no problesm shutting off over several years until a couple of weeks ago. I had stopped driving it daily about a month ago when I fixed the AC in my truck which is now my summer daily.

Symptoms remain identical with the door lock lines bypassed. Only thing left is the brown lines to and from the ignition lock and shut off valve on the pump. Am able to shut off instantly when connecting the mityvac directly to the shut off solenoid with only one or two hand pumps. Shuts off the fuel flow at about 5 Hg's consistently. Leads me to conclude issue is neither the, pump, shut off solenoid, brake booster, nor door lock issues, which leaves either the two brown lines themselves and their connections or the ignition lock switch.

- Peter.

[Jason240d]

If you connect the two lines together that go to the ignition shut off valve and the engine shuts off. Then it is the valve that is the culprit. If it doesn't shut off then you have a leak some where in your vacuum lines.

[Diesel911]

Originally Posted by pj67coll

When you say steering column lock. Do you mean that entire contraption in the picture?

- Peter.

Yes, the big end with the hole in is where the Ignition Switch goes. Note I don't know at what year it stars but on some years like my 82 W123 you also need to have the Key in the same position as it would be in to remove the Lock Tumbler to get the Switch out and that is besides the 2 screws that need to be backed out.

Also when my Steering Colum Lock broke inside when I inspected the Ignition Switch one of the contact points on the switch was entirely burned off.

New Steering Colum locks generally come with a new Ignition switch and a new Vacuum Shutoff Switch but be sure to read the ad closely.

[Diesel911]

The below supposes that there is enough vacuum available to begin with.

2 of the tests to see if it is the Valve on the Steering Colum Lock or the Vacuum Valve/Servo on the Fuel Injection pump are:

T a Vacuum Gauge into the Vacuum Line going to the Vacuum shutoff Valve/Servo. If when you turn the Key to the shutoff position you are not getting vacuum either your Valve is made or the Vacuum shutoff Valve/Servo would have to have some large holes/crack in it.

Next is to remove the vacuum line to the Vacuum shutoff Valve/Servo and install a separate line and apply vacuum to that line and see if it shuts off the Engine. While this is better done with a Mighty-vac type tool so that you can actually see how much vaccum it takes to shut down some people have simply sucked on the line to see if it shuts down.

Note on mine some for at least 5 years Oil passes through the Vacuum shutoff Valve/Servo diaphragm indicating that it has porosity (you will find Oil in the Vacuum lie if that is the case). I would not expect it to hold Vacuum if tested with a Mighty-vac. However, it has always shut off reliably.

[tyl604]

I do not know the 240D; I have an '81 300SD and I had the same symptoms. Turned out to be a bad shutoff valve - the vac assisted valve in the back of the injection pump which has an L shaped lever which pulls and shuts down the engine. I refused to believe this was the problem because I had just replaced my original shutoff valve (35 years old) about six months earlier.

So I too asked the forum about the shutoff on the ignition switch. Uniformly they said do not remove it, that it almost never goes bad. They said I could pull the dash cluster and maybe the rubber connectors to the ignition switch were leaking but emphasized that the shutoff on the ignition switch almost never goes bad. Then they mentioned (as I remember) that you have to basically remove the steering column on an SD to get it out.

I did replace those rubber connectors even though they were not bad. But the ignition switch turned out not to be the culprit. It was a Chinese made shutoff valve that lasted only six months. I replaced it again and have not had another problem - this is maybe a year later now.

So, assuming the 240D has the same type shutoff valve, I would pull the vac line off it and attach the Mityvac. If you cannot pull a vac or if it leaks, that might be your problem. I would do that first. Hope that is the problem because it is an easy fix.

[pj67coll]

Originally Posted by tyl604

So, assuming the 240D has the same type shutoff valve, I would pull the vac line off it and attach the Mityvac. If you cannot pull a vac or if it leaks, that might be your problem. I would do that first. Hope that is the problem because it is an easy fix.

I had already pulled the vac line off the shut off solenoid on the back of the injection pump and attached the mityvac directly to said solenoid. It shuts off immediately at 5 Hg's pressure with one or two pumps of the mityvac consistently. There is no sign of oil in the line which leads me to suspect it's not the injection pumps shut off solenoid.

I have taken today of work and I will attempt to find some golf tees and vacuum lines to continue troubleshooting.

- Peter.

[pj67coll]

I have bypassed the ignition lock vacuum switch by disconnecting the brown purple line from the injection pump shut off solenoid at the ignition switch and extending it with some vacuum line I just bought behind the heater box into the passenger footwell area. Actually the passenger kneewell to be more exact as it protrudes into the passenger area just next to where their left knee would be right where the center console meets the dash.

I attached the Mityvac to that line and shut off the car by hand pumping. Works like a charm. So I believe there is nothing wrong with either the brown purple line itself, the shut off solenoid on the injection pump or the rubber connection pieces. The only thing left is the switch in the ignition assembly.

I'm not in a position to tear into that right now so it will have to wait. For now I will simply shut off the car by hand using the Mityvac which will reside on the passenger seat. Looks a bit odd, but works fine and as I almost never have a passenger in the car it's not in the way of anything.

- Peter.

[tyl604]

With luck it might be the rubber connectors between your plastic vac lines and the ignition switch. Let us know.