560 sel won't start
 

1990 560sel replaced the head gasket now car won't turn over. replaced the neutral switch not sure if i have it on correct. how do know for sure the switch is the problem? I turn the key and all you hear is a clicking noise. The guy i bought it from says he had the starter replaced. It cranked and i drove it home, took it apart fixed head gasket, put back together and nothing happened. A friend messed with the neutral safety switch and it turned over a few times, so he told me to replace it and i did off another car - this car cranks. Still nothing! What else do i try? Very frustrated and need help bad!