I've been spending the better part of 2 days trying to sort out the vacuum issues and I have a question. According to the diagrams that I have, the ignition vacuum is a closed loop. ie. no other vacuum lines branching from the system. To shut her down, I have to take a hit off of the br/blue line and that does the trick. If I plug the lines in the switch as they are intended, the system doesn't work. So, is it possible that the component that the lines plug into is at fault,and/or the cam that is inside the switch itself? Without removing the ignition, how would I verify this is the problem?
Vehicle: 1982 300TDT 150,000 miles 1985 380SE 130,000 miles 1991 560SEL 81,000 miles (a/k/a the nightmare)
Location: Massachusetts
Posts: 1,657
Is there oil in the brown-blue vacuum tube? When the diaphragm in the shut off valve on the back of your IP goes, oil is allow through it, and into the vacuum line. If you can apply vacuum directly to the valve, and the car shuts off immediately, the valve should be good.
The valve on the ignition is relatively cheap, and rather easy to replace if you've got the right driver for the screw bit. Also, make sure the vacuum tubes are not cracked, and that the rubber vacuum hose connections are tight, and not dried out.
And not that I'm a proponent for taking hits from anything or anyone... but you really should not take hits off of the vacuum tube... you don't need any of that oil in your lungs... An automotive syringe works great.
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I've been spending the better part of 2 days trying to sort out the vacuum issues and I have a question. According to the diagrams that I have, the ignition vacuum is a closed loop. ie. no other vacuum lines branching from the system. To shut her down, I have to take a hit off of the br/blue line and that does the trick. If I plug the lines in the switch as they are intended, the system doesn't work. So, is it possible that the component that the lines plug into is at fault,and/or the cam that is inside the switch itself? Without removing the ignition, how would I verify this is the problem?
you don't have to take out the ignition. just the panel there, it's tough, but doable.
Applying vacuum to the line and it shutting down would lead me to believe that the injection pump diaphram is good, no? There is no oil in the line from what I can tell though. I did remove the panel under the dash to investigate. Really not much room under there is there? I have a spare ignition valve, maybe I'll plug the lines into it and see how that works before rippin and tearin.
Do you have a Mityvac? If not, you need to get one. You must know if you're getting vacuum, if so how much, and if elements and circuits hold a charge.
Do you have any other symptoms such as doors not locking, vents not flopping, etc?
If applying vacuum directly to the valve at the IP shuts off the car (and no oil is in the line), then that part is good. Next, test the valve at the ignition. Apply vacuum to the brown line under the hood leading TO the ignition and see if you lose vacuum. Check to see if vacuum from a known source like your Mityvac will run the system. Find out if it's in that circuit or something else.
Last edited by Gregs300CD : 10-10-2007 at 10:22 AM.
Yea, I've been dragging my feet on the mityvac. I guess I gotta break down and buy one if I'm to sort this thing out. I'm just sick of dealing with the gremlins and figure it's time now that I've got the windows, sunroof and a few other hvac related things fixed to dive into the vac system.
Do you have a Mityvac? If not, you need to get one. You must know if you're getting vacuum, if so how much, and if elements and circuits hold a charge.
Do you have any other symptoms such as doors not locking, vents not flopping, etc?
If applying vacuum directly to the valve at the IP shuts off the car (and no oil is in the line), then that part is good. Next, test the valve at the ignition. Apply vacuum to the brown line under the hood leading TO the ignition and see if you lose vacuum. Check to see if vacuum from a known source like your Mityvac will run the system. Find out if it's in that circuit or something else.
I can turn mine off only by pumping the ever-lovin' crap out of the mity-vac. Doesn't matter where I connect it, before or after the ign. switch. The only other culprit would be the vacuum lever inside the IP I guess?
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Did you try drawing vacuum directly from the shut-off valve itself?
The rubber connectors might leak, or the diaphram in the shut-off valve might be split.
Do you notice any oil in the line?
Unfortunately, all the vacuum systems in these cars are interconnected. A leak in one of the actuators of the climate control systems can badly affect the engine shutoff operation. Do as advised by others: Get a vacuum test pump, test the valve first by itself. Then, if the valve if good, proceed to the ignition lock solenoid vacuum valve.
Do you have other symptoms, like harsh transmission shifting, slow or inoperative door locks, or improper air flow through the A/C registers? If not, chances are, your problem is the shut off valve itself.
Warning: if the shut of valve is defective, do not try to replace it by yourself unless you know exactly what you are doing!!!! The reason is there have been cases where people hooked the valve actuator arm too far on the pump rack and as soon as they started the engine, the engine went to full throttle and raced itself to utter destruction! There is no way to shut off a runaway diesel unless you immediately block the air flow. So, if you chose to replace the valve yourself, make sure you know how to do it, and before you start the engine, disconnect the turbo elbow and stand by the intake with a telephone book ready to immediately block of the air intake should the engine start racing.
Also, one should not attempt to shut off a runaway diesel as it can be extremely hazardous. Better a blown engine than a serious injury.
Vehicle: 1982 300TDT 150,000 miles 1985 380SE 130,000 miles 1991 560SEL 81,000 miles (a/k/a the nightmare)
Location: Massachusetts
Posts: 1,657
Good piece of advice P100... I would never have guessed by some of the other posts I've read that the diesel could run away if the shut off valve were installed improperly...
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