wiring trouble

on my 1977 280e when i try to start the car, it cranks fine but when i let off the key it keeps on cranking,even when you take the key out of the ignition. could someone lend some helping advice

a starter relay or solenoid, possibly also the key switch. Is the starter the only thing still running when you turn the key off?

a starter relay or solenoid, possibly also the key switch. Is the starter the only thing still running when you turn the key off?
no, the motor is still turning over.I found some burnt wires, replaced them but still doing the same thing. starter was rebuilt could it be a bad solenoid. check the ignition seems ok. do you know werew i could get a wiring diagram for the ignition system te chiltons manual does not give a good enough break down. thanks for the reply