I got a pump un stuck. Didn't take as much as I thought it might, but this could vary depending on how crummy the fuel was, etc...
10,000uF charged to 15V connected to the pump with less than 2 feet of total wire. [Low resistance is part of how to get a big impulse of energy in a short time] This pump didn't run when I had tested it with straight 12V a year or so ago.
Using the capacitor, I could have gone to 24, 36, or even higher. The shortness of the pulse would limit the heat to avoid burning out a winding, But the short burst of higher voltage would give it a bigger kick of torque momentarily.