Options from an electrician
Voodoou,
There are 3 or 4 wires connected to the back of the opel starter solenoid. Two of them are rather large ones, one to the (+) of the battery (labeled 30) and the other into the armature of the motor itself (really short, uninsulated thick wire oppisite the battery one, going directly into the motor) Some starters have only 1 more (labeled 50) that goes to the start position of the ignition switch. Others still have a fourth one (labeled 16) that goes to the positive terminal of the ignition coil.
The first wire, from the battery, is self explanitory. The second big wire is the one that actually sends power to the starter motor. It is also attached with a 13mm wrench and should be identifiable.
The third one is the next one you need to test. Disconnect the 1/4" spade connected terminal farthest from the block (labeled (+) in you picture) and connect the (+) of your multimeter to the wire (not the terminal) with the (-) connected to a good chasis ground. Have a friend take the ignition switch to "start" and you should get +12V. If not, I'm sorry, you will need a new ignition switch, and they are really hard to come by. (You might need to get friendly with someone sitting on 2 NOS ones

) If you did get +12V at the wire, then the starter is immediatly suspect! (this is a good thing!)
Assuming the ignition switch was fine, reconnect the #3 wire you just got done testing, and disconnect the last small wire (if you have one.) This wire is to supply +12V to the coil, bypassing the in line resistor wire, to give you a "hotter" spark at start-up, but only for a limited time (to prevent burning-up your coil.) Some cars don't use them, some do, even after 30 years the verdict is still out on whether or not it is necessary.
Now with the 4th wire disconnected, if you have one, and the one from the ignition switch connected, find your helper again and have them take the ignition switch back to "start." Keep the (-) of you meter on a good chassis ground and check the 2 big and 1 small (if present) terminals on the solenoid. All 3 (both) should show +12V, and the starter should have "clunked." If they do the solenoid is fine, the starter motor is bad (still a good thing!) If the big terminal on the bottom doesn't show 12V, but you did get a clunk, you still may be fine, you will just have to recondition you solenoid (easy to do, really.)
If you got +12V on every terminal but the motor didn't turn, now is the time to make a decision. The motor is bad, but $60-85 at any auto electronics rebuilder will get you a rebuilt motor with no worries. If you won't or can't spend that then read on, we'll rebuild that motor together!
If the solenoid was bad you can do one more check with the starter in the car. Use your multimeter to test the resistance from the ignition switch terminal of the starter (labeled 50) to the big terminal closest to the starter motor. If you get much more than 10 ohms, the solenoid is really dead, you need a new one. If it is less than 10 ohms, around 7 say, we are still in business. This is the resistance of the coil, and the coil is hard to replace.
With a good resistance on the solenoid coil, it is time to start taking apart the starter itself. the first step is to remove the solenoid, which you do by taking the 2 screws at the flywheel end of the solenoid loose. When you get the solenoid off, clean the goo out of the screws on the terminal end of the solenoid and remove them. There should be a copper bar inside that is usually the problem with an Opel starter. It will probably be very pitted and corroded, especially after sitting for a few years. File or sand it to a nice polish, along with the terminals inside that it contacts, and put your perfectly working starter back in!
If the motor was the problem you will need to dissassemble it completely and clean the commutatur, where the brushes ride against the rotor, with a pencil eraser. Attention to detail is key, as is some ammount pf patience. It can be trying when small parts spring out at you.
If you attempted all of this, and now you have a pile of motor parts you don't know what to do with, let me know. I'll send you my address, and you can send me the motor to refurbish it or I can just send you another. One of the major skills the Navy did teach me is how to recondition DC motors!
