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Discussion Starter #1
So I've given up on trying to find my keys. I had two keys for the car, one worked with exterior locks and the other for the ignition. When I started to call around and try to get a replacement key, I was rightly told that I shouldn't have two diff keys like i do. I knew the tumbler was a replacement for they did a lame and conspicuous job purtting the new one in. So now I have no keys and my only option is to buy a new tumbler and key and since I need door keys as well, I have to go through MB via my VIN to get the parts....or do I?

The thought occured to me that maybe I could simply install a switch or button to start the car. A three function switch that would be off, almost on/light her up, and then start. Just like our keys do. I've been jumping the starter to see if I can crank it without the key. Almost there. Of course the steering wheel is locked, but I can unlock it by grinding. I would love to be able to bypass the usual start method and use a button or switch. I don't care about someone stealing it because I can hide the switch or place it in view and no one will understand what it is. I can leave the ignition key slot as is. I have an odd switch that is attached to the side of the console near the gear lever. I don't know what it does and I think it was for an after market alarm or stereo. Anyway, that's when the idea hit me.

Has anyone done this? Is is it possible?
 

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My father has done this to his 91 Toyota truck with an Allen Bradley switch, and I've wanted to do it as well, but I ran into the problem of how to shut the car off. Your 83 300D is shut off via a vacuum actuator at the injection pump. The vacuum is applied when you turn the key all the way to the left.

You could simulate this by using a pneumatic/electric solenoid like the ones that your car uses for the vacuum control of the climate control system. I think you could definitely do it, and please post your progress on this.
 

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Discussion Starter #4
Thank you c.

I gave up on my lost keys and looked up how to hotwire it. I couldn't let it sit anymore. So while I was researching how to hotwire it, I stumbled on the "jumper junction" posts and I tried that instead. I've been trying to get it to start that way. It'll crank, but I cannot get it to turn run for any real length of time.

Today, it occurred to me that I just need a switch of some sort. Some thing that will behave just like my key, but different of course. I connected the jumper wires to a small 12 volt on/off switch I had and put one wire to the on side of the switch and the other wire to the off. When I flipped the switch, the connection was made and I was able to try to hotwire it, though this time with a switch, not just a jumper wire.

It seems to me that this should be easy. I think three setting switch of some sort is all we'd need. It's all running on 12 volts and it seems like one could simply use the existing wires from the tumbler and connect them to a switch. I was able to do it jumping to the solenoid, so why not further?
 

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another thing to consider...

is that the pre-glow system (your glow plugs) is not engaging in your attempts to jump the car. That's likely why it's cranking but not turning over. You'll have to figure out the pre-glow system as well with your custom switch. It would seem it's a lot easier to bypass the key-start system on a gasser...
 

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Discussion Starter #6
True. It would be a lot easier on a gasser, but I'm thinking about what I'm going to have to do to get a new key and tumbler put in. Given the choices, I'd like to find a different way.

Seems to me that if I can get my glow plugs to warm up for a few seconds, I could jump the car. If I can do that, why not bypass the whole key starter system and do it all by a switch. I've seen a manual glow plug over ride system available for purchase on a website we all may know. If I can manually start the glow plugs and manually jump it, why not go all the way and skip the key? Can't be too difficult. Then I can call MB and give them my VIN and just ask for a key to use for the doors and trunk. That would be $15-$18 bucks and I'd have a futuristic super ride!
 
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