Start with disconnecting the:
1. Battery charging alternator.
2. Both electric fuel pumps. The set should run for 15 min, on just the day tank.
3. The IP, like Ray wrote above.
4. The fault indicator. It should pop its own fuse, if something is bad. Unless its over fused, or has tin foil wrapped around it.
5. Look at CB1. That's the 7.5 amp circuit breaker. Look at the wires going to it. Are they showing signs of being hot? Look at where the CB1 wires go through the relay table. VERY often, the plastic ring that is supposed to protect the wires going through this hole, is gone. Some times the wires get worn through. Sometimes they make contact after a while because of vibrations.
6. Look at the doors. Yes the doors. The inside of them. Mainly its the left side rear door. The wire harnes, often is loose and the wires touch the door. The wires vibrate, and wear through. Sometimes they touch the metal door. You can see signs on the door where a wire arc's. A burn spot, if you will. Pop goes the CB1. Ask me how I know this.
7. Replace the CB1.
8. If by then you have not found the problem, start looking at every wire harness that goes near metal.
If that brings no joy, we can really start digging.
