Grrr!
So annoying when you think you've sussed a repair but it doesn't work!
Richard, the only capacitors I've seen blown are the metal type found in Hoovers - sometimes the ends get blown out, also seen the capacitor can burst at its seam. There's also an electrical smell that lingers, and a sooty discharge round where it blew.
There is probably a centrifugal switch on the motor shaft. When the motor is switched on the switch is in the closed position, and energises a set of secondary windings at a different phase, inducing rotation. Once the motor is up to speed, the switch disengages as momentum keeps the motor going. A stuck switch can damage the secondary windings, maybe that's causing the big bangs?
Have you tried powering it up again? If you do it with the capacitor disconnected, the motor will hum but not turn, but if you give the rack a turn by hand (presuming you can disable the door switch) the motor should start running.
If there's a short somewhere you usually get sparking from the location of the short, was the machine dry both times? Have you been able to poke it with a multimeter at all?
Hope you can get this sorted, sure you will though!
Simon