tripac apu troubleshooting help

not sure if this is the right place to ask or not but i just bought a 07 kenworth with a thermoking tripac apu the unit will crank but doesn't start. everything i've found online pointed to the fuel pump but that didn't fix it so i checked for power and ground at the fuel pump plug and am getting continuity to ground on both wires. after following the wires an not finding anything cleary wrong or shorted i i unplugged the fuel shut off solenoid and the continuity to what should be the positive wire at the pump went away. does this mean the shut down solenoid is bad? i've searched online and unable to find a wiring diagram since i don't know the exact model of the apu