no spark, no fuel

[smooov]

so i have a 1988 325i and it has me stumpped. i did an over rev when i missed a gear and i ended up breaking a rocker arm on my cam shaft. so i did a head swap and replaced pretty much the whole top half of the motor but when i put it all back together... i had no spark and no fuel. we couldnt figure out why it wasnt starting so we took it down to a local shop. they replaced the harmonic balancer and it had spark again, then we went on a wild goose chase for a motronic computer, found one, replaced it and it had fuel again. so the car started up, ran perfect for about 15 minutes and then it was shut off. we put it up on the rack because there were a few nuts missing from the wiring harness, we replaced them and tightened them down. after we pulled it off the racks, we had the same problem as before... no spark and no fuel. my friend at the shop was baffled and decided that he couldnt fix it so i had it towed back to my house and before i break down and take it to a dealership, i wanted to reach out and see if anyone happened to have some sort of idea about what is going on. any input at all would help. thanks guys

[E30_fiend]

did you check the main relay?

[jlevie]

No spark, fuel pump not operating, and injectors not firing means that the DME has no power or it doesn't see timing data from a rotating engine. That suggests a problem with the CPS or main relay.

[smooov]

thank you guys for your help, im going to check all this out, see what i come up with and i'll let you know how things go!