Can I Disable the Starter Lockout Function
 

In the stock configuration, there is a re-start lockout function on the ignition that prevents re-engaging the starter without first turning the key to the OFF position. I'd like to be able to do a restart without doing so.

I have a manual shutoff switch and a manual glow switch so I don't need the functionality to either shut off the engine or enable glow plugs with the ignition. I'd like to be able to just restart without going back to OFF.

I know I could add a manual starter switch but I'd like to keep the ignition key to activate the starter, just without having to go back to OFF.

Don't care if the solution also disables the steering lock - don't need that either.

This is on my 617 powered 107 which has an ignition module virtually identical to the 123 just without the vacuum shutoff bits.

Interrupt probably the IGN HOT line to the starter module with a normally closed momentary operation switch, or replace the starter module w/ a simple relay suitable to the starter solenoid load. Or if you find that the starter solenoid load is within the current fusing and amp capacity of the starter switch and associate, just bin the starter module and run a line from the crank wire to the solenoid.

When you take my ELECTRICAL advice, keep in mind the fact that I went to school for and work in MECHANICAL engineering. Any fires or damaged components that result are your own damn fault for not asking someone who knows better.

Or just labeled switches on the dashboard:GLOW, CRANK, KILL, and wired accordingly. Use the key to switch IGN hot only.

What you describe sounds exactly like what happens if I try to re-engage the starter on my 300SD without cycling the key. It physically will not allow me to turn the key into the start position a second time. I have not taken the ignition tumbler apart on one of these but it should be able to be disabled by removing the mechanism that stops the key on the second turn. I know that is a kind of "no duh" answer but I do know that people have removed the steering lock successfully. I believe the two features are unrelated, though.

I'm hoping that someone has had one of these apart and can suggest something that can be modified to eliminate the lock-out. As I said in the original post I know I can add a manual switch to override, but I'm hoping that there is a mechanical mod not an electrical mod.

From what I can tell the old school (12x chassis) anti-repeat on the starter switch is all mechanical. There is a contact that goes straight to the starter solenoid (and the glow relay on Diesels). There is nothing electrical in the circuit on the 123 or 124 that I can see that would interrupt the starter solenoid signal based on key rotation a second time.

Now on the 210 and newer with the electronic key that interlock is probably all done electrically as a function of the DAS module.

I too think that its mechanical. At least on my w126 and my w123 it felt as though it was.

Do you plan to leave the key in the switch on a permanent basis?

Or does your engine just require frequent and repeated use of the starter?

No I don't plan on leaving the key in all the time. I've got a supplemental set of gauges that run using a bluetooth connection between a microcontroller mounted in the engine compartment and an old Android phone. The connection can be finicky when reconnecting, so every time I shut the engine down the gauges may not reconnect reliably. Once it's connected it's bulletproof. I'd like to be able to leave the ignition on during short stops to keep the gauges active. Don't want to leave the microcontroller on all the time and risk running the battery down.

http://www.peachparts.com/shopforum/diesel-discussion/350205-engine-instrumentation-project.html

Question
 

Why not install a 2-3 valve like I did in the shutoff vacuum line of my daughters 300D.
http://www.peachparts.com/shopforum/diesel-discussion/321775-welcome-fleet-1976-w115-114-300d-dark-green.html
The engine will never shut off, unless you close the valve, regardless of key position.

http://www.peachparts.com/shopforum/3151302-post78.html

Manual Vacuum shutdown switch
http://i21.photobucket.com/albums/b2...ps7825b621.jpg

.

I can here a click in the car when you turn from the start position, that didn't start the car, back to the off then back to the start. it has to be a latching relay, what about finding the hot lead from the switch to that relay and switching that? the relay would think that you had switched the car to off then back to start....

It's purely mechanical. I have an ignition module off a 123 on the bench and it has the mechanical lockout functionality. I may attempt to open it up, but wanted to throw the issue on the brain trust before doing so.

Already have a manual shutoff. I used a vacuum solenoid in the engine bay with a switch in the cabin. I want to restart without cycling the key if possible.

Power it directly off the battery/fuse/on/off switch = problem solved?

Like mechanical interlocks do not exist?

What powers this "latching relay" when the battery is disconnected? (The switch behaves the same way, battery connected or not.)