I have an older air compressor that runs on 220 volts and has a three wire plug. I have a 5500 watt generator that has 4 prong 220 outlet. I am trying to put a 4 wire plug on the air compressor. I can't seem to get the right combination for the wiring.

Use: X, Y and ground. Ignore the neutral, or white. If you have a 4-wire cable hook it up in the plug, but do not hook it up in the compressor. In fact, there will be no place to hook it up to.