Hi there, my dad was driving and all of a sudden the truck shut off we have fuel but no spark, got new distributor and nothing and all of a sudden no spark at the coil and then there is. Its so weird. I get combustion(back fire) at times when I turn the key off. We suspected a bad switch got one that works but no difference. We tested the coil and resistor and they are fine. I can here the relay click. All this and still no spark what am I missing here? Also I put a test light to the possitive on the coil when switch is on and light turns on.