Hey, if you guys could help that'd be great!

My 1983 300SD was starting up great and then, after I filled it up, it lost all power. i was jump started and made it home where i plugged in my charger, after a while on the charger, the battery was full and all of my electrics work fine until the key is turned. everything dims down and the car wont turn over.

Its got a brand new starter and battery and a fairly new alt.

If you've got any ideas let me know