I just acquired a 520H that ran for an hour. After sitting for a few days it started right up and quit after 5 seconds. Turn the key and nothing happens. If it were a fuel problem it would at least turn over. It won't even make a 'click' of the solenoid.
I'm guessing the problem is electrical. Battery shows 12.6 volts. Load test for 10 seconds and it still has 12.2 volts. Battery contacts are clean.
Have not checked the 'engine ground yet'. Haven't found it yet.
Loosened and re-tightened cable connection at starter.
Found the 30amp fuse severely burned. Replaced it. Still nothing.
Cut the wires to the seat safety switch and soldered them together. Still nothing.
Suggestions welcome.