240D shutoff valve on the ignition lock. - Page 2 - PeachParts Mercedes-Benz Forum

pj67coll · #16 04-23-2018, 05:24 PM

Not likely. As I pulled the rubber connector off the switch itself and connected the new vacuum line to that connector. I'll report back in time when I finally get around to tearing into it in more depth.

- Peter.

scottmcphee · #17 06-22-2018, 11:48 AM

Quote:

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.

Thanks for this explanation of the vac lines as a SPDT switch.

I am pretty sure I've reversed the lines after working on the ignition key mechanism on my w124 300D.

With reversed lines a key-off will still always connect vac to shutoff lever for a correct shutdown. But when lines are reversed, when the key is turned to run position vac source is connected to bleed and lever line gets subbed / capped by the valve mechanism (acting as if to pinch it off).. so that line continues to hold vacuum which holds the lever down. So car won't restart until enough vac bleeds out of the shutoff branch to allow the lever to rise up again, slowly over time, like overnight. This is exactly what I'm seeing right now.

For my car if it rests for a while (lever lifts a bit) it will actually start and run with a "mostly held down lever" but car is gutless and powerless and feels like a bad ALDA (which has been removed, by the way), or restricted fuel, like clogged filter, or air bubble entry into fueling, or turbo not spooling up to make pressure... those kind of symptoms.

So the drive cycle effect of reversed vac lines at the ignition switch is this:

- car starts easily in the morning after a normal dose of glow
- car runs fine with good power
- turn off a fully warmed car after reaching destination
- it shuts down fine
- immediately trying key to restart... it won't.. cranks and cranks and cranks
- try again cranks and cranks
- try again cranks and slowly comes to life, low idle weak revs, low driving power - THE LEVER IS SEMI DOWN
- let car sit overnight, lever rises
- repeat

Observe and test: when the lever is semi down rev the car by pulling the accelerator cable while under the hood, and you get weak revs. Now lift the lever up manually, and tugs on the accel cable gives good revs.

Confirm the issue: while under hood, pull vac line from shutoff valve leading into the cabin, this releases vacuum on the line, and you'll see the shutoff "STOP lever" rise more fully. Car will now start fine.

This was my observation today that I did in the parking lot when I got to work. I logged onto this forum, and ... thanks forum! Such a wealth of knowledge here.

scottmcphee · #18 06-24-2018, 02:50 PM

Quote:

Originally Posted by scottmcphee

Thanks for this explanation of the vac lines as a SPDT switch.

I am pretty sure I've reversed the lines after working on the ignition key mechanism on my w124 300D.

With reversed lines a key-off will still always connect vac to shutoff lever for a correct shutdown. But when lines are reversed, when the key is turned to run position vac source is connected to bleed and lever line gets subbed / capped by the valve mechanism (acting as if to pinch it off).. so that line continues to hold vacuum which holds the lever down. So car won't restart until enough vac bleeds out of the shutoff branch to allow the lever to rise up again, slowly over time, like overnight. This is exactly what I'm seeing right now.

For my car if it rests for a while (lever lifts a bit) it will actually start and run with a "mostly held down lever" but car is gutless and powerless and feels like a bad ALDA (which has been removed, by the way), or restricted fuel, like clogged filter, or air bubble entry into fueling, or turbo not spooling up to make pressure... those kind of symptoms.

So the drive cycle effect of reversed vac lines at the ignition switch is this:

- car starts easily in the morning after a normal dose of glow
- car runs fine with good power
- turn off a fully warmed car after reaching destination
- it shuts down fine
- immediately trying key to restart... it won't.. cranks and cranks and cranks
- try again cranks and cranks
- try again cranks and slowly comes to life, low idle weak revs, low driving power - THE LEVER IS SEMI DOWN
- let car sit overnight, lever rises
- repeat

Observe and test: when the lever is semi down rev the car by pulling the accelerator cable while under the hood, and you get weak revs. Now lift the lever up manually, and tugs on the accel cable gives good revs.

Confirm the issue: while under hood, pull vac line from shutoff valve leading into the cabin, this releases vacuum on the line, and you'll see the shutoff "STOP lever" rise more fully. Car will now start fine.

This was my observation today that I did in the parking lot when I got to work. I logged onto this forum, and ... thanks forum! Such a wealth of knowledge here.

I popped the instrument cluster out to get at the 2 vac lines on the ignition switch, and reversed the order so it's now correct... and no surprise problem solved. Car stops normally, and will restart again immediately after as it should normally.

pj67coll · #19 06-25-2018, 05:15 PM

Quote:

Originally Posted by scottmcphee

I popped the instrument cluster out to get at the 2 vac lines on the ignition switch, and reversed the order so it's now correct... and no surprise problem solved. Car stops normally, and will restart again immediately after as it should normally.

Nice to see you had an easy fix.

- Peter.

Saturnfan · #20 06-29-2018, 12:04 AM

I've had that little part screwed to the ignition fail on two of my cars now, including my current 240D. When you turn the key off to "0" it just dumps vacuum right out the side...