anyone replace vacuum switch-off valve on ignition switch? - PeachParts Mercedes-Benz Forum

amg280 · #1 03-10-2008, 04:05 PM

My 300D 2.5 has a leaky one, and sometimes it wont shutoff. We traced it to the little switchover valve on the ignition switch.

It looks impossible to replace, what is the best way to do it?

rldbenzofohio · #2 06-23-2008, 12:45 PM

I also traced the vacuum leak to the ignition switch. I have tried getting to the switch but the dash configuration is winning.

Have you had any success yet?

amg280 · #3 06-23-2008, 01:34 PM

I did have success. If I remember correctly, you have to first remove the instrument cluster. After that, remove all the kick panels in the footwell, including all the trim directly behind the ignition lock (part of the kick panels. Remove the 2 electrical connectors from the ignition switch. Then, remove the cable that goes from the ignition switch to the shifter assembly. After that is all done, you have to remove the giant plug from the rear of the ignition switch. To do this, the key has to be in the ignition and in position 1. Lastly there is a 10 mm bolt you have to loosen to free the igniton lock assembly from the steering column. Loosen that, then press down on the little release tab to free it (key should be in ignition and still in position 1. Once released, removed the key for clearance. Also, you may have to remove part of the airbox (there is a "rubber" tab that pops off, you will see it).

Once out, it takes 2 seconds to swap the vacuum element. Oh I forgot to mention to remove the 2 vacuum lines going to the switch. Remember which way they go!!

pdrayton · #4 12-27-2008, 03:08 PM

Can i ask a question?

My ignition vacuum switch over valve seems to be a problem too. The supply and return line to the ignition switch are fine, so is the shutoff valve (tested with mityvac.

So i'm thinking it must be the ignition vacuum switch. But I'm a little concerned it could be something to do with the new ignition switch I put in. It works fine except that it doesn't spring back from START like it should. You have to manually move it back to RUN after the starter has started the engine.

Is there anyway that could be the problem? Another reason I'm doubtful is with the ignition off, the switch doesn't hold any vacuum. With the ignition in RUN, it holds vacuum. Does that sound like a broken vacuum switch? I'm not sure what it is supposed to do.

What section is the ignition in the FSM? I've looked and looked, didn't find it anywhere.

Thanks,

Paul

pdrayton · #5 12-28-2008, 10:26 AM

Thanks! Section 46, the one I didn't look in...

pdrayton · #6 01-06-2009, 07:41 AM

I replaced the vacuum switch and got the ignition switch out without removing the instrument cluster on my 1992 300D W124.

You just remove the under dash trim thing and then you can get the ignition out. Look in section 46 of the FSM - it explains everything, including 'previous work' which is what needs to be done to get the ignition out.