Why would a fuel fuse keep going?

Answer 1

fuses are made of tin-lead, like solder. they melt when they are heated up to melting point by the energy of the excessive current. Assuming the bus voltage is still 14V from your voltage regulator, the only other thing that could jack up the current is a decrease in circuit resistance where the current is going. so your "Fuel" circuit is at a lower resistance than it should be. This is a normal wear and tear condition for a pump motor or a relay coil to get into over a long period of time. whatever is the primary load downstream of that fuse will need to be replaced. (not a switch or the contact path of a relay, that is not the load, just a gating device) A load is a coil, a motor winding, a heater element, a light filament, something that consumes electrical energy in the form of heat, light, mechanical energy, or the like. The load has degraded insulation resistance and is passing that extra current to ground, or it has degraded series impedance, and has lost its efficiency converting electricity to work, and so now it draws more (a bit too much) to get the job done. Ohm's Law.