I arrive on a no heat service call. I go to start the system up to verify where on the sequence of operation the boiler fails. The call for heat comes on. Afterward, the flue damper opens. Next, the aqua-stat relay powers the pump and gas valve blowing a big spark at the pump. I find the pump is shorted and needs to be replaced so I replace the pump. Purge all air out of the system and start running the heating system. Unfortunately the short damaged the storage tank and it started leaking when I was heating up the boiler.