90 bmw 535i won't start

[lilcallaway]

Just did an engine swap-m30 out and another m30 back in.
Car wouldn't start. Thought it was the starter because I could hear the solenoid click, but then it stopped. I had the starter checked and it was fine. So I thought it was the ignition switch. Made sure I had all tight connections and whoila, the car started. I turned it on and off about four times and after the last time, it hasn't started back since.
I have headlights. Checked the fuses, nothing blown. Got the battery recharged and still nothing. I retested the battery and ended with a new one. Switched ignitition switches and still nothing.
Thanx in advance....

[icesoft]

Auto-transmission range switch or starter relay?

[lilcallaway]

I guess that's about the only thing I haven't checked is the starter relay. I'll look into that next.

[Kalevera]

Check the ground strap, make sure it's tight and secure, or do a voltage drop test, chassis against the engine (front lift hook is best).