I have a 1981 w123 240d with a manual trans. I parked it for a few hours and when I turned the key to the start position nothing happened. The solenoid didn't click and the starter motor didn't spin. The battery seemed to be charged and the instrument cluster lights were on.I tried bridging the solenoid and starter motor connections on the starter with a wrench and nothing happened but a few small sparks, nothing like the sparks you usually get when you do this. I was on a hill so I started the car by rolling it downhill and popping the clutch, As I drove home the idiot lights on the dash were off and the alternator seemed to be charging. When I got home I killed the engine and tried to restart it. It started in the usual way and started several more times. I went back to the starter and bridged the solenoid and starter motor connections as before. This time the starter motor spun but didn't engage the fly wheel. The solenoid didn't throw.. Do solenoids sometimes work intermittently or do they just go dead? Does anyone know whats going on here? Thanks for your advice.

 

You have a bad battery.