ignition switch help - PeachParts Mercedes-Benz Forum

#1 09-26-2004, 03:14 PM

I have a 1975 300d that has a bad ignition switch, I think. The car starts fine but has to be shut off manually under the hood. I ordered a new switch. I need help or advice or directions or pictures on how to remove the dash to get to the ingition switch.
Thanks-
--- Eddie

#2 09-27-2004, 10:11 PM

.bump.

Palangi · #3 09-27-2004, 10:15 PM

Most likely a vacuum leak, maybe the shutoff solenoid.

JamesStein · #4 09-28-2004, 10:42 AM

A shutoff problem is not in the ignition switch. Assuming what you are refering to is the electrical switch and not the vacuum valve on the ignition.

It is most likely vacuum related.

Did the problem start right after an oil change? If so you likely have some vacuum lines disconnected. Check them all.

If thats not the case you need to check for vacuum leaks. Door lock system leaks can kill your shutoff. AC vacuum leaks can kill your shutoff. You might have a vacuum leak on the brake booster, or the EGR or the transmission. All these things can and will stop your car from shutting down properly. Before you actually replace anything you need to do a quick check of the vacuum system.

If you don't have a leak then you can start looking at the shutdown components themselves. Valve on the IP, valve on the ignition.

If your sure the part you have is the source of the problem, you can get some information about the dash/cluster ignition removal at http://garnet.acns.fsu.edu/~jjs5772/W123

Thats more geared to ignition problems... but it explaines how to get the ignition out.

#5 09-28-2004, 03:58 PM

thanks...now where is the vaccum hoses going to the ignition assembly and ow do i get to it. Sorry i'm a MB noob.

-Eddie

meltedpanda · #6 09-28-2004, 04:04 PM

on the back of the injection pump. see if there is oil in the line,a good sign the diaphram is leaking. Be careful when replacing, runaway engine can result.
Also make sure no lines have been knocked loose.
I once knocked off a hose while working on my radio that resulted in the engine not shutting off.

JamesStein · #7 09-29-2004, 11:31 AM

If you get up under the lower dash panel you can see where the valve on the ignition switch is. Unfortunately I don't have a good picture of it. Just one thats pretty darn fuzzy.

As you can see in the other picture, the yellow vacuum lines go to the door lock system. The green w/yellow line goes to control the AC pods.

The first thing I'd try is to plug off the AC and the door locks. (Golf Tee's work great for this, as you can see in this picture my wifes door locks are plugged). See if you can shutoff then. If not, than the problem is elsewhere and could still be a number of things other than the shut-off valve on the IP.

You'll want to get a vacuum pump (MightyVAC). It makes tracking down vacuum problems so much easier and will also allow you to test out the shut-off valve on the IP and the one in the ignition.

Palangi · #8 09-29-2004, 01:11 PM

FWIW, the car in question is a 115 chassis, not a 123. Although the basic principal is the same, I'm not sure that things are necessarily located in the same place or color coded the same way between models. I think the 115 300D may have a pnumatically governed injection pump, which might be a little different than a 123 300D.

JamesStein · #9 09-30-2004, 09:13 PM

Opps.. I didn't even notice the year.