Joe G said it best. The heater holds about a half cup. It can't heat up the fuel that has already gone past it and is stored in the pump, the line to the filter, the filter, the line to the injector pump, the fuel in the injector pump and the lines from the IP to the injectors themselves all which together hold a couple of quarts. All that fuel is cold soaked when you first fire up the engine, so if it will start then what need is there for a fuel heater? Do you really think that little heater can effectively heat the fuel coming from the tank once the engine starts? How much amperage do you think that 16 gauge wire will carry? Oh, and don't let the TX location fool you. I spend way too much time in the great white north, in fact I'm in northern ID tonight enroute to the mountains of northern WY, which takes me thru MT.

 

I think the main purpose of the fuel heater is to slightly warm the fuel as it passes through the fuel filter, where the minor pressure drop and restriction would tend to cause wax formation when the fuel is already at a borderline temperature for gelling.

I have seen many problems with overheating fuel heater electrical circuits and, while I have never done a current draw test on a damaged circuit, I believe the overheating to have been caused by excessive current flow due to a heater element that has shorted. I would recommend replacing the element as well as the damaged wiring, if the heater is to be made functional again.