Help with electricity question: spa pump and capacitor

So, help me not dump another 500 gallons of hot tub water into my back yard.



I had everything fixed-- for a day. Then, I got an error code on my spa that indicated water wasn't flowing through the primary pump, and so the heater would not turn on. After one minute of running, it trips the GFI, which makes sense.



I primed the pump-- that didn't work.



I note that the pump impeller is spinning, but I still get the error message. My internet research says it must be the capacitor. So, I drain the tub and get at the capacitor (I did read enough to know to short it first).



Questions: 1) If a capacitor sparks when you short it, does that mean it's good?



Mine gave a pretty loud snap when I put a screw driver across it.



2) If the pump impeller is spinning, can the capacitor still be bad?



I know-- get a volt meter. Gonna do that tomorrow at Home Depot, but none of this makes any sense.



So, I'm confused as to how water can't be flowing through the pumps when the impeller is spinning?! I'm guessing it can't be the (cheap) capacitor...

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