I've determined that the shifting/shut-off problems i'm having are not the vacuum valve at the IP pump, as i just replaced it. What happens is that the car is slow to build vacuum after sitting for a while. Also, it is slightly slow to shut off. I'm only reading 7" of vacuum to the shut-off valve. So i'm fairly sure it's the ignition vacuum switch. I have pulled vacuum on the shutoff circuit (by sucking on the line to the switch) and the s/o lever goes down, so it would seem it's hooked up correctly to the ports at the vacuum switch. Also, i'm getting 20" Hg to the switch from the booster line.

Am i on the right track? Any tips on replacing the ignition vacuum switch?

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Mike
Vancouver, BC
'79 300td 60k miles!
import from Japan

A leak somewhere, notoriously difficult to find, start by removing the door locks. A yellow plastic "thing", check valve, near the firewall by the brake booster.

EDIT, remove the door locks from the equation, as has been suggested.

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83 SD

84 CD

I would hold off on the ignition vac switch. Try plugging off the door lock system, the yellow line, and then start the car and see if the car shuts down. The plug the the climate control system, the green line, and try shutting the car off again. You may have to plug both and then try shutting the car down as well. If any of these yeild the car shutting off properly then which ever system is plugged off is leaking. And you should investigate that system more. It may be both systems.

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thanks..actually both systems are plugged off, and it still is slow to shut down and also shifts intermittently....i've isolated the other components, and replaced all the vacuum lines/fittings..

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Mike
Vancouver, BC
'79 300td 60k miles!
import from Japan

I replaced my vacuum valve at the ignition switch. I might have been able to get away with just replacing the soft lines at the switch that connect the valve to the hard lines. Try that first before ordering a new valve.

My soft lines at the ignition valve had been oil soaked from the shut-off valve leaking, causing the flexible vacuum lines to swell.

Pull the panel below the dash on the drivers side - put the seat all the way back and contort yourself to take a look up underneath. (Or maybe pull/push the instrument panel - I don't remember how I got at it!) You'll see the vacuum valve attached to the ignition. Replace the couple of inches of soft lines on each side of the ignition valve.

If that doesn't work, and you've isolated the shut-off valve (it sounds like you've done this), try to attach your vacuum tester to a piece of soft line and connect it to the "input" side of the ignition valve and, with the ignition in the "off" position, see if you can pull and hold vacuum. Then do the same on the line going to the shut-off valve. If the shut-off valve holds and the ignition valve doesn't - problem is found!

But again - replace the soft lines at the ignition valve first - might be a simple fix. btw - I advocate "pushing" the instrument panel out to remove it.

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83 300d - 390k

Thank you...I have replace all the vacuum lines, including the lines to/from the shut-off circuit. Also, all the rubber soft lines. As i said, i put a brand new shut-off valve in and there was still only 7" Hg to the shut-off line, while there is 20" going to it. Also, that 7" slowly leaked, so i think i've found my problem. The original shut-off valve is back in the car--there is no oil leak, and it works just as well as the brand new one..so I think indeed i have found my problem.

Ok, so do i remove the lock cylinder to get at the vacuum switch or just remove the vacuum lines and squeeze my hands and 90˚ screwdriver in there to remove the switch from the lock?

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Mike
Vancouver, BC
'79 300td 60k miles!
import from Japan

I believe you can get to it with a 90* screwdriver but you will probably also need to remove the instrument cluster to give you more access.

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I agree, pushing the instrument cluster out is safer and easy. Not sure about 617s but on 240Ds the spedo cable is secured with a plactic clip in the engine bay. (or is, spoz too be) Cut that lose to give a little more slack, unless you have very small hands.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Yup, i'm an expert on getting the cluster out (took my twice to remember hooking the oil pressure line on before starting though...doh!)..it's just the switch replacement.

thanks

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Mike
Vancouver, BC
'79 300td 60k miles!
import from Japan

Well, i've got a brand new ignition vacuum switch, can't hurt. However, still intermittent vacuum. Shut-off works great now when there's vacuum!!

I'm going to break down and order a new vacuum control valve...I've isolated everything else, including constant 20" vacuum at source from brake booster. All new vacuum lines. The vacuum control valve works fine when it actually holds vacuum, but sometimes there's just...nothing...

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Mike
Vancouver, BC
'79 300td 60k miles!
import from Japan