Okee dokee
Before I seal everything up and move on I thought I'd add pics of my connector to this thread, as well as my thoughts. You can clearly see how the heat melted the plastic, and how the one disconnect migrated across to its mate.
Very similar to the other pics posted.
So, my read on this is as follows:
1. A foreign, rubbery 'doomahicky' in the tank finds its way to the inlet of the fuel pump and plugs it. Perhaps this item isn't fully compatible with gasoline, meaning it might take years before it relaxes and releases from it's intended location.
2. The extra load causes the contacts inside the electrical connector to heat up. These are of a very simple design, with little electrical contact area; Their current-carrying ability is way less than the adjoining wire, hence they become the hot point in the circuit.
3. Any more fuel than (say) 1/3 of a tank means this connector is submerged. In this case I believe the fuel acts as a heat sink, slowing or preventing the heavily loaded contacts inside the connector from melting the plastic. In any event, the load is less than the 20 amp fuse in the circuit.
4. At 1/4 tank or so the connector is no longer being cooled by fuel. Maybe the occasional splash/slosh contributes a bit. Eventually the heat build-up at the plug contacts causes the supporting plastic to relax, and in short order one contact migrates toward its mate, shorting the circuit and blowing fuse 4 in the rear SAM. I have trouble imagining that these wires did not spark as they touched. Insert exclamation point here.
Also contributory;
I note that the wires to the pump are zip tied such that there is strain on the pump disconnects. The strain may further minimize the effective (electrical) areas in contact with each other, and contribute to the migration upon the plastic melting. I'm going to see what I can do about that strain when I reassemble.
Also, I noted absolutely NO driving symptoms of a partially plugged fuel pump. Mind you at less than a quarter of a tank I'm generally not on the gas that much.
Anyone with this problem notice symptoms of fuel starvation prior to?
Ideally I'd run a current regulated supply across a test disconnect and see how hot things get at 20 amps. But I don't have one and time's a tickin' so I'll go with what I surmise at this point. I fly RC electric ducted fan jets (40A at 11V all the way up to 100A at 22V under load) and would NEVER use this kind of contact for 40A,
probably not even 20A. I use Anderson Power Poles owing to their superior design in this very area. Bottom line; I "expect" the contacts at the pump connector did get HOT. Yes, hot enough to melt plastic. And then they shorted.
Finally, does anybody have any last words for me before I commit the next several hours to the R&R?
tn