Presently I am on a business trip and my wife has my '83 TD at home. The car, intermittently, wont shut off by the key. She knows to shut it off by the emergency lever in this situation, but only has to do this every so often. How can a vaccuum problem being intermittent? I ordered and it was delivered to my house, a Mighty Vac tester. I'll be home next Friday to dig into this. The door locks are also intermittent. Is this a sign of a pump on its was out? Any help would be greatly appreciated.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

Could be the vacuum pump or check valve. More likely a vacuum leak, like in the door lock system. When the engine will not shut down, try locking the doors. Or unlocking them if they are locked.
Vacuum leaks can certainly be intermittent. How are the power brakes working? If they are okay, the vacuum pump is probably okay also.

Sounds like that pesky IP Shutoff.
Easy to test with a mityvac.
Only $35 from ***************
Make sure you read CAREFULLY install info an threads here, you don't want to end up with a run away moter.
I worried about doing it myself for a month, then finally did it.
Piece of cake.

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Think Alternative Energy!
300CD '80 (now gone but not forgotten...)

That's what vacuum EXCELS at. Being intermittent.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

My wife didn't mention any problems with the brakes. Short of a pump going, how can vaccuum be intermittent. I figure a leak is caused by a hole, so how can a hole be there one minute and gone the next. I consider the vaccuum sytem as mechanical in operation so either it's broken or not. Electronics can be intermittent, loose connections, broken wires, etc.
Would a faulty shut off valve affect the door locks? When I get home next week, I would like to know where to begin troubleshooting.

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

There can be a number of factors that can lead to intermittent vacuum problems. First, the system has multiple "circuits." The circuits are used in varying combinations. For example, a door lock system has a "lock" circuit and an "unlock" circuit. A leak in the "lock" circuit might not manifest itself when the doors are unlocked, since the plumbing with the leak is not being used. The same is true with the vacuum actuated components in the ventilation system. You could have a leak with the heat on, but not with the A/C on. Secondly, the leaks are often caused, not by holes, but cracks in the rubber components. When the rubber is relatively warm, the crack might essentially seal itself. In colder conditions, the rubber becomes stiff and the crack opens. Some rubber diaphrams are streched in one position and compressed in others. A small crack might only cause a problem when the diaphram is streched. Thirdly, there are a number of check valves in the vacuum system. A check valve can stick some of the time, and not stick at other times. This is not uncommon with the check valve at the vacuum pump. But when its fails, everything that is vacuum operated will be affected, including the brake boost.

It is not likely that the shut-off actuator would cause problems with your door locks. The door lock system is isolated via a check valve. What is far more likely is that a leak in the door lock system (or elsewhere) is causing the shut-down problem.

Here is where to start. Disconnect the vacuum line to your shut-off actuator. Connect your vacuum tester in its place. Start the engine. Apply vacuum to the shut-off actuator. If the engine shuts off, the actuator is not the culprit. I would then see if the door lock system holds vacuum. I am betting that it will not.

In the interim, ask you wife to lock the doors the next time the engine refuses to shut down. That sometimes will do the trick.

My Ex Wife owns, an '84 300TD. Almost an identical car as yours. On several occasions she would park the car in the garage, but the engine would not shut-off. it only would happen occasionally.

One day, I found out what was causing it. She would inadvertently, with her elbow, depress the door lock button part way down. Pressing the door lock button only half way creates a vacuum leak and prevents the engine from shutting off. Lowering, or raising the door lock button fully, allowed the engine to shut-off.

Maybe, just maybe your wife is inadvertently also doing the same thing.


Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

One way the IP shutoff could affect other vacuum systems, is if it has been going for a while, and sucking motor oil into the system extensively. It is amazing how much oil over time can get in and travel all over the place, wreaking havoc. Don't ask me how I know.

__________________
Think Alternative Energy!
300CD '80 (now gone but not forgotten...)