No, a short at the pump wires, regardless of resistance, is not the cause. If it were, the 16A fuse would instantly blow. High heat is always generated at the point of high resistance -- poor connections at the relay socket terminals and the fastons at the fuse block, or even the fuse ends.

Slightly warm is probably OK, but "probably" and "slightly" are meaningless guesses. Whatever could have burned your fingers, that is where the problem existed. Just warning you, a re-seating or even retensioning of these connectors is not a permanent fix if they got hot enough to melt plastic and solder. The temper needed to maintain contact force at the crimp and at the terminal is already gone from the connectors.

I say it is a common misunderstanding because so many folks blame the load for hot connections. There are suggestions to "upgrade" by adding a cube relay to "take the load" from the k-jet relay, thinking Volvo somehow under-designed it -- and they get believed and appear to work because doing so replaces the faulty wiring and connections with brand new wire and fresh terminations. The root cause is a leaky windshield in most cases, as the wiring loom is the drain path for the leak, so between moisture and age, anything carrying significant current is afflicted by poor connections and high contact resistance.
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Art Benstein near Baltimore

A good wife always forgives her husband when she's wrong.-Rodney Dangerfield