Pestering question....

Wondering what a fuse goes to....

91 yj 4.0

The MAXI fuse that is numbered "Fuse F2" under the hood is the only fuse that sparks a little when I pull it out meaning there is a closed circuit some place.... I can't figure out where it goes. The cover for the fuse block says "I.O.D." and I can't find it anywhere in the wiring diagrams in Chilton's book for this vehicle. What does this fuse protect? It is the fuse furtherest from the end and is one of the two 20 amp fuses on the line.

Only reason why I am wondering is that there seems to be a power loss in the system some place. First thing I looked at was the fuses. This is the only one that has current flowing through it (closed) all the time, but doesn't go to the lights/clock/radio backup....

Puzzling....

Any ideas?

As for what brought this on, well, hard to crank... push-starts just fine... Shorting the solenoid rapidly with a metal stick of sorts tends to get it to start, but only with a charger on "jump" mode.

Battery is new and is rated with plenty of CCA's. Wires for engine ground and battery to starter are new and can handle more than my house can (tripple O) and all the relays and fuses seem to be just fine....

Ignition switch? Perhaps....