W126-

My 1986 420SEL was running fine when I parked it up indoors a few months ago. Since then I've done some suspension and brake work, and fuel filter, but nothing under the hood. The battery is a decade old so it requires a jump, but when I hooked the cables up the wire connecting the alternator output to the fuse box immediately went up in smoke.

Disconnecting alternator output the short disappears and I'm able to crank the vehicle but there is no start. Replaced OVP fuse and inspected the rest, fuel is good but I'm not getting spark. CPS tests good (900Ω) but I'm getting no voltage across the coil primary inputs. (well actually it goes from zero to 0.4mV upon crank).

Can anyone provide relay and wiring diagrams so I can fault find a bit better?
thank you.