today the 84 volvo had a small electrical fire, and i'm trying to get it going again. the car stalled, the driver pulled off the road, switched it off, got out, and then the engine started cranking all by itself and smoking until she disconnected the battery.
so far, i found problems in the harness that crosses under the bottom of the engine, in the following wires: alternator output, alternator small wire, oil pressure switch wire, ignition resistor wire. all of these have been repaired, and everything else in that area appears to be ok.
the problem i still have is no spark, specifically no power the the + side of the coil. the - side of the coil seems to be getting proper signal, as a test lamp placed between the coil - and the battery + will flash while cranking, as it should.
all fuses are good, fuel pumps run, but i can't get a spark to get the darn thing going. i tried jumping power to the + terminal of the coil, with no improvement
any suggestions to help find the problem? i'm going back and forth between the car and the wiring diagrams, and not having much luck

 

Between the battery and the + side of the coil you have distribution block on the fender by the coil, the fuse connections, and the ignition switch.

 

it looks like there's more going on here than i first thought. yesterday i went to check something on the car, put the battery on, and heard a quiet sizzle. i studied for awhile and found it coming from somewhere in the harness under the intake manifold. i didn't manage to find the exact point, but suspect there's another large meltdown in there. i also found that the dashboard warning lights were all half-lit with battery connected and key off/out.
at the junkyard i found a wire harness that i plan to clean up and just replace this one. i got the ECM and the ignition module with it, just in case i might need them

 

Well, you're definitely going about it in the right manner. Volvo did make new and improved insulation versions of the engine harness. According to davebarton.com, the o.e. harness was 1348296 or 1348297. The new version was 3515397. The under crank pulley region is a known trouble point for the harness with all the oil leakage over the years. Many folks choose to reroute that portion of the wiring rather than continually mess with it. Good luck!

 

today i rebuilt the replacement wire harness, and learned a few things about them.

on the replacement harness, the only wires that were bare are the ones that connect to the firewall connector (the 8-position bullet-connector unit), all 5 of the wires from there were bare for at least half of their length, while none of the wires coming from the computer or from the ignition module showed any damage at all.
this leaves me thinking that someone would do well to make a harness that only replaces that part of the factory harness, and price it at half the cost of a full harness - it would sell real quick!
anyway, all of the offensive wires were replaced, i taped the harness back up how i found it, and then tore the burned-out harness out of the car and installed the new one. everything went fairly smoothly, and when i went to start the car, it started right up.
now its all back on the road and doing well, and the spare ignition module and computer i picked up can rest in the back shed somewhere