Wiring & Fuse Observation

[pbanders]

In helping Scott with his ECU/fuel pump problems, I noticed something - the power supply to the ECU does not have any fuse in the circuit. Current comes directly from the battery, through relay 74 (when ignition key is "on"), then it goes straight to the ECU.

If anything goes in the ECU, wiring harness meltdown is very likely. Adding an in-line fuse doesn't seem like such a bad idea.

Anybody ever have a problem with this circuit melting down?

thanks,

Brad Anders

[bowlsby]

That sounds like it might be wires #16 and #24 in the FI harness?

Of the dozen or so harnesses I've disassembled and of the more than 50 I've inspected, occasionally those wires exhibit signs of heat stress. The PVC wire insulation is occasionally wavy and slightly distorted for want of a better description.

What is equally interesting is that once in awhile, I'll see a harness with certain ECU wire terminals on the harness wiring that have rather severely discolored from the original silvery zinc plating to what looks like an overheated (bluish) steel. I can only imagine the intensity of heat in those connections because the heat would have to come from electrical sources, as the ECU connector is, of course, well insulated while its connected to the ECU inside the metal ECU housing.

[DDS]

The heat is a function of current and resistance, so more current or more resistance (corrosion) or both = more heat. More heat means faster corrosion and so on...
The highest current in a car is drawn by heaters or motors of any sort. Keep those contacts clean and the terminals tensioned.
Dave