cranks wont start

[rrbacon]

installed a 1981 3.0 motor in a 1979 733i. Motor cranks but wont start. I have fuel an spark. It will fire with starting fluid. Have had two mechanics look at it that didn't know what the problem could be. Any suggestions appreciated. This motor came out of a 1978 was running and starting fine.

[yert315]

Check injector pulse. If you have fuel at the rail and it only fires when you spray starter fluid in the intake, the injectors aren’t doing their job. I’m not too familiar with the early electronics, but I’d look at fuses and crank sensor to start.

[rrbacon]

thanks, will do

[Willfox69]

My car is doing nearly the same thing except I don’t think my injectors are firing maybe because I tripped the obc lock? I believe it’s getting enough fuel as I can feel the lines rushing and stuff. But it feels like it’s just running the fuel through the line. Not the injectors

[Willfox69]

So I believe my car has nearly the same issue.. my fuel is just going through the fuel line and not firing over.. maybe the injectors aren’t firing? Could I have tripped the obc maybe?

[rrbacon]

I found the problem on mine... a wire connection that was not intact under the dash on the passenger side. It was just luck, when I put the connection back together it fired right up and running good. I think it must go to fuel injectors.