1985 500sel
 

my 85 500sel will not run i cheked for compression it was good im getting good spark and gas to the injectors. the only thing that i found was when i turn the key the fuel pump will not run but if you jump the fuel pump it will run. is there a sensor or somthing that is stopping it from running?

500 SEL
 

Check the fuel pump relay, should be a black box inside the fuse box just behind the firewall on the drivers side. Give it a tap with a screwdriver a couple of times and see if you can hear the fuel pump turn on. The fuel pump relay is the most common cause of the fuel pump not turning on. You can run tests on the relay, but i have no idea how to, maybe someone else can chime in with that answer!