A week or so ago, I was tinkering under the hood and the engine shut off. It refused to start, so I assumed it was a fuel or spark problem. After checking all the wiring and testing the ignition coil, I found that the ballast resistor on the ignition coil had fried, causing about 4 volts to the coil, instead of about 13 volts. This meant that the engine was not getting any spark and would not start. I bypassed the resistor and it has been perfectly fine since. I do keep a spare coil in the cab in case it dies, but no issues so far.