Glenn,
I was reading your post quickly as I was being called to dinner and I did not have the time to think the problem through before I responded and then had to run.
When you said that you disconnected the pump and changed out the relay and still had the issue that would seem to rule out a weak breaker as a cause. It would be good to have a dc ammeter to insert here and there or a clamp on version to see if you can sort out where the current is going. If I remember right (I do not have a DC schematic either) the relay system steps on and off with a pulse from one of three swiches that are in parallel with each other allowing you to turn the power source on or off from any of the swich locations. At least that is the way it works in my Marquis.
You could disconnect the output wire from the breaker at the panel, and run a long length of external wire to the bay and feed the pump with that and see if it works without tripping. Assume that is good, then add the relay circuit with the external switches disconnected and trigger it with a length of wire and see if that is all good. If that works then if the switch feeds are individually wired to the relay you could add those one at a time. If they are tied together elsewhere, pulling a wire off each of the external swiches, one at a time may isolate which switch wire run may have caused the short if that is the source. If you can get it to work with one of the switches disconnected you may need to live like that and use the others.
If it turns out everything works normally with the diagnostic DC wire feed from the breaker to the pump relay, you may find it easier to add an inline breaker and run a seperate DC feed from the battery bank. Hope ths helps.
Later Ed
