I purchased a 2007 F650 service truck with maintainer service crane. Drove it 2000k miles from VA to MT. No issues. Then the ignition starts acting weird and won’t start the truck. Starter relay can be jumped to start and runs fine but I have an ABS light. Occasionally started then just stopped working. I have 12v to ignition switch, but only 6v at starter wire out of the switch when I turn key to start. When i depress the clutch it grounds the signal. I don’t have a service manual or wiring diagram available. I can’t seem to find it online. Seems like a ground issue somewhere. Anyone have experienced similar? This truck has 200k miles and been fiddled with I’m finding some wires taped together and lots of cut random wires. I am just at wits end any help appreciated.