No Junction Box , Solenoid signal wire bad!
 

So , this 1983 W123 euro 300d non turbo doesn't have a junction box. and the starter doesn't get a signal when the key is turned. The starter is good and using a Jumper wire from the battery to the solenoid signal terminal, the starter turns and the car starts. Here is the best part: when you do turn the key, you hear the Glow plug relay "pong" a.k.a click off. so the "purple wire " gets the signal from the key. I need to replace that White signal wire. but no junction box is really making things difficult. Anyone know what to do?

Check your neutral safety switch and if that's ok, clean the contacts in the ignition switch. There's a thread on here somewhere describing how to do it with pictures I believe.

no neutral safety switch , ignition switch is obviously good since the glow plug relay clicks off.

the solenoid wire must be broken somewhere, but how far back is the purple wire for glow plug relay and the white starter solenoid wire connected?

no neutral safety switch , ignition switch is obviously good since the glow plug relay clicks off.

the solenoid wire must be broken somewhere, but how far back is the purple wire for glow plug relay and the white starter solenoid wire connected?

Most people who have this problem with their ignition switch have reported that the glow circuit works with the switch but the starter doesn't. It's a different set of contacts that engage the starter. The picture in the thread about resolving the problem shows which contacts need to be cleaned.

You should not assume there is an open connection quite yet. You may be getting some voltage though to the activation terminal. Then either your solinoid has grown very tired and wants to see more voltage on that line than is present or oxidized connections are present.

It is quite common in fact usually normal for the solinoid trigger point to be lower in voltage than the general battery voltage. Manufactures save a little money by using a less than desirable wiring size assuming the solinoid or anything in the circuit is never going to age and require more potential to activate. Just like when you used a direct temporary wire it did get a full 12 volts or very close. . So measure the voltage present at that starter terminal if any with a meter. With the key in the start position obviously.

Do put your negative meter probe to the negative terminal of the battery . If you have a ground issue the meter might read less if you put the probe to the valve cover instead for example. Only after then then put the negative probe to the valve cover to verify the grounds are good. . If so the voltage reading obtained should be identical to the last reading using the negative battery terminal.

Again I suspect the grounds are probably at least fair as the starter did roll well with the jumper. It just never hurts to check for the time involved in my opinion. After doing this type of proceedure once it takes only a minute in the future to duplicate the test on the same car or another in the future.

If say nine volts is present with the key turned to the start position. You find out in the archives if that is substandard or average. If average there are two choices. Pull the starter and repair/replace it or wire a ford starter relay positioned on the interior fender to supply a higher voltage.

Now there is even a step before that. A tired ground between the battery and car body or from the body to the transmission might be semi involved. Either clean them. Or for a temporary test establish a solid ground test connection. This is done using a good booster cable from the negative battery terminal to the engine at a place you are sure the clamp is connecting ground electrically.

I know your battery is okay as when you bypassed the trigger circuit the starter preformed well. This eliminates corrosive problems at the battery terminals pretty much as well. The usual cause of many starter problems.

All the above steps are easily preformed and do verify what the actual problem is. This is all based partially because you might think that it activated with the jumper wire so logically there is no voltage at the terminal in the start position. You may have already verified that with a meter or might not have. Assuming nothing is a good approach to problems in my humble experience. Also in responding to members questions. We have no way to know your experience level and what exactly you have or have not done.

I usually try to give answers that are pretty comprehensive taking the risk that the poster knows more about what is going on than myself. If so there is no intent to sound knowledgeable or superior. In far too many cases the poster knows far more than myself. There are the few occasions this is not so. The logic better safe than sorry does apply when responding. I can only hope I recieve the same treatment when posting questions.

If the main Stater Power leads are not up to snuff ( have corrosion , Etc ) Is it possible for the solenoid terminal to pull more power ( voltage and or current ) ?? Because it felt like there was a lot of juice being pulled through the wire I was using. ( which happened to be a solid 14 gauge , not stranded. I found it in my tool box, it was left over house wire )
It made a decent size spark when I tapped it on the battery terminal and it did get warm. How many amps should that solenoid pull?

I doubt anyone on site has measured a normal solinoids current draw. You might have to ask a starter/alternator rebuilder. It is reasonable to me that age might increase the required current draw to function. Further reducing the voltage at that point with the factory loop.

The state of the main starter terminal connection has nothing to do with the solinoid activation until the electrical/mechanical motion of the solinoid closes a switch to spin the starter. That is what is not happening in your senario.

no juice what so ever at the solenoid wire. It's broken somewhere. On cars with Junction box, I see the white solenoid wire and the purple glow plug wire connected, so can I just run a wire from the solenoid to the glow plug relay purple wire? I guess for the time being until I really Replace the old white solenoid wire. and how do I replace the white solenoid wire, on cars without a junction box, where do the purple glow plug wire and the white starter wire get connected?

anyone have a clue?

My guess is that the most likely place it is broken is in or at the ignition switch so I'd pull the electrical part of the ignition switch and do some testing there.

ARINUTS,

Once you sort out the "Trigger" wire from the Electrical portion of the Ignition Switch,Acquire a Bosch WR1 starter relay kit.
(Shortens the circuit to the
starter solenoid AND does not route the High Amp draw THROUGH the Ignition switch anymore.)

Instructions for wiring are for VW s ,but Same Same in MB.

http://www.oldvolkshome.com/hardstart.pdf

Picture credit to Glenn over @ The Samba.com