[truckster]

Start simple. As SheepDip said, start with battery connections. Use a test light to check for 12v at the starter switch. Verify that the "run" position is energized. Verify 12v when you turn to the "start" position. Make sure you get 12v at your fuel relay when the key is initially turned to the "run" position.

In other words, perform a trace from where you know you have voltage (the battery) to where you lose voltage. That's going to be where you problem is.