I think that some of the smoke you were seeing at the time of failure was all of the magic blue smoke leaving either your sequencer and/or the ESC.

The switching on and off is hard on the ESC due to the start up surge every time the pump motor starts. You want an ESC that is rated at least 3 or 4 times what the full speed running amps WHILE pumping smoke fluid of the pump. Most ESC can handle 1 or even a few quick starts in a row, but continuous pulsing will cause an over heat since every start is an over current condition.