Jim;
Sounds more like a fuel starvation problem.
The coil can heat up and fail, if you have a "resistor type" rotor (and I don't know if Volvo used them or not)it could be "opening" and failing.
Resistor (carbon) spark plug wires can break-down and fail, but one usually notices it long before it gets to the point of not starting.
Since you were messing with the ignition components, I'd go back and make sure you disn't get grease or grunge on any points of electrical contact (rotor tip, dist cap center and the four lugs, on the points (is so fitted), etc.
Check for a loose wire going to the dist, and it's lug, as well as the "pig-tail" wire inside the dist going to the points.. this can become frayed and ground out, it can also break and cause intermittent contact..
Back to the fuel.. If you are running the Bosch FI, your fuel pressure must be spot on.. otherwise the injectors won't spray, they will just drip.. Be sure your fuel pump is working and the fuel pump relay is kicking in to turn the fuel pump on, etc..
Double check the "double points set" that is located in the bottom half of your dist, and the elect plug-in.. these are the points contacts that actually "fire" the injectors..
Good Luck.
Charles.