I looked at a thread :
http://www.peachparts.com/shopforum/tech-help/322947-1978-280sl-fuel-pump-relay-wiring-info.html, and determined that I should jumper terminal 30 & 87 on the fuel pump relay connector. I did just that, and it started right up and ran until I removed the jumper. Does that mean the relay is bad? I also read something about an "air horn safety switch" or something like that. The car is an '85, and not a '78 that the thread was talking about. Any ideas before I order a fuel pump relay?