can anyone help with this problem? I have just put the engine in my Beetle after a long restoration and the engine would only run if the key was held on. After looking at every wiring diagram I could find, I couldn't find the problem. I then changed the wire coming from the 50 terminal on the solenoid to 30 on the ignition starter and the wire from the fuse box to 50 on the ignition switch. The engine now starts and runs normally but it doesn't match with any wiring diagram I can see. I would rather fix it now then have a problem when I have the car finished.

30 = permenant live (normally from term 30 on the light switch)
15 = Switched Live (Ignition ON) this will go to any switched live terminals in the fusebox and also to the ignition coil in the engine bay
50 = starter solenoid
X = (only on later vehicles) accessory live, does sidelights and few other things from memory

Thank you for your help.
I had the permanent live on the 50 terminal. Now that you have cleared it up, I can't remember why I set it up like that. However I had convinced myself it was right.
When I changed it, of course the engine ran as it should and I was still convinced it was wrong. Once I realised the 30 was the live it made sense. So thanks for that.

no worries. i know what it's like when your brain is stuck on a certain train of thought.

Glad it all works now