Very often when I turn the key of the ignition and no matter whether it starts or not when pull the key back the starter won't stop. I keeps rotating until I remove one of the wires from the battery. I have no idea where to start looking. Is it mechanical ot electrical. Please help!

 

Sounds like the starter solenoid is sticking causing it to keep cranking .

 

or maybe the starter gear is pressed so hard against the flywheel that it cant retract to its normal position. I'd jack the car up and put another shim in there. You could put a voltage guage on one of the starter wires that only gets voltage when you turn the key. If the volts stay at 12 and dont drop back down to zero after you turn the key it might seem like you have an electrical issue. That does not sound like a fun wire tracing job... I hope its just a shim. 89-bird might be right too, luckily the parts and labor for that is cheap.

 

It not just doesn't retract the gear, but keeps rotating, meaning it's recieving electricity from the solenoid. I hope it's just the solenoid.

 

It cant be the solenoid

There is only one wire that activates it, the heavy purple wire. When there is no power across this wire, the solenoid will not activate

Test this when you are under the car via multimeter

It sounds like you have a faulty IGN switch on the column

 

when I reatach the wire to the battery the starter does not start again. if i there was a switch stuck and sending signal to the solenoid wouldn't it start sending again as soon as the power is back on?

 

Yes it would so therefor your problem is the solenoid is sticking in the start position and when you remove power it stops and resets . Basicly your contact points are sticking in the solenoid when they have power and when you remove the power it unsticks .