Arrgh: New Shut Off Valve in 85-300D; Still Wont Shut Down
 

Back again. Many thanks to those who have commented.

Replaced Shut Off Valve in Cali-model 85 300D. Needed replacement (needed tons of vac to work, and was leaking oil into vac system).

Good news is I replaced valve the right way (no runaway).

Bad news is I still have no shutdown. Valve works perfectly (got it to shut down just by sucking on the vac line with my mouth).

Where do I look now? Vac pressure does not need to recharge with driving does it? Did the oil migration foul up the pressure going through the key cylinder?

Annoyed.

Gently disconnect the brown line from the brake booster line check valve. Start the engine then turn the key to OFF. The engine should stay running. Draw a vacuum through the brown line to see how much it takes to shut-off the engine. If you have a vacuum gauge, take a reading at the check valve on the brake booster line where you disconnected the brown line. Report back.

Sixto
87 300D

Temporary solution: Get a piece of long rubber vacuum hose. Attach it to the shut off valve in place of the brown vacuum line. Run the end of the hose out of the hood at the cowl. When you want to shut the engine off give it three good sucks. Fix your lack of vacuum to the valve at your leisure.

Didn't see the original thread, but did you ever check the vac line where it connects to the ignition switch? They can fall off and it would cause this also.

Your vacuum cutoff cylinder in the key switch could be stuck with motor oil. Check the brown line if it has vacuum then check the brown-blue line. If the brown line has vacuum, you should also get vacuum in the brown-blue line when you turn the engine off with the key.

That idea with the vacuum hose running to the cabin from the valve -- to turn off the engine by sucking -- did occur to me, right up until I remembered this is my wife's daily driver (when she gives me my car back). That could be weird in any number of ways.

Ok, so the place to start is tracking back to the cylinder? It does have engine oil in it from the faulty shut off valve (drips visible). I did check the brown line to make sure it was attached -- and it's a biatch getting my hands in there -- and it is attached. Should the brown line have vac when car is at idle or just when key turns to off position?

I hate vac issues. Hate them.

Yes, the brown line should always have vacuum when the car is running.

The shut off system is quite 'simple'. I spent a long time to figure out my new W124 toy as the PO butchered up the vacuum hoses.

1) The brown hose going into the cabin's ignition. It should always has vacuum as it is tee-ed from the brake booster. It has residual vacuum even when the car is off.
2) The brown hose returning from the ignition to the shutoff valve varies with ignition sw position.
a) Key off or 0 - vacuum. It is fed by the incoming hose thru the shut off valve at the ignition sw.
b) Key is in starting position. No vacuum. vacuum is vent to release IP shut-off.
c) car running - No vacuum.
d) All this is controlled by the mechanical shut off valve attached to the ignition sw.

Hope this help.

So I checked a few things:

• Good vac coming off the brake booster line to the four way
• I believe this is right: lighter brown line attaches to the four way before the dash and goes through fire wall and presumably delivers vac to ignition. I have the brown line with blue stripe coming out of the fire wall attached to the shut off valve (which is now brand new).
• The brown line with the blue stripe does not have vac when the key is in either the on or off position (presumably it would only have vac when the key is in the off position, to actuate the shut off valve)

So if this all seems right, the problem seems to be that upon moving the key to the off position, the vac delivered by the brown line is not being transferred to the brown/blue stripe line, and hence the car is not shutting off. If the vac cutoff cylinder is gummed with engine oil, how do I clear? Is that the likely culprit? Could a check valve be clogged? I replaced the ignition cylinder last year (not easy to get at). Not again.

This link may help. I think it could be the mechanical ignition shut-off.

http://www.peachparts.com/shopforum/diesel-discussion/205191-how-fix-shutoff-problem-ignition-vacuum-switch.html

The valve on the switch is in post #3 here:
http://www.peachparts.com/shopforum/diesel-discussion/314017-vacuum-line-question.html

I sprayed brake cleaner through that line from the engine compartment to the removed line.

I concur. Spray brake cleaner through the brown lines.

To be clear, am I spraying brake cleaner to just clear the lines (i.e. so I would detach them first and spray through them) or ... am I spraying brake cleaner hoping it will also clean out the mechanical ignition shut off (i.e. I would not detach the lines behind the dash -- I would simply spray brake cleaner into the lines from the engine compartment? Thanks, this is very helpful.

Just to clear the lines of accumulated gunk. Be sure to detach the lines from the ignition switch, rig up a catch can, go under hood and spray. If you feel ambitious, spray the valve on the ignition switch, that may be tricky, don't get any on ya.

You replaced the actuator (mechanical ignition shut off), no need to clean that.

Why not spray the cleaner right thru the switch on the ignition?