I had the same experience with the Craftsman "SUV floor jack". At around two years age and a dozen uses on the bird, it wouldn't raise or support weight and it was weaping at the pump handle piston end of the power head. I found the instruction book and visited Sears online to buy a new power head. They listed the part as costing the same price as the new jack. And then it was not available for order anyway. There was a section for customer reviews on this product and comments were all unfavorable. One owner reported one of the steel wheels it rolls on "exploded".

I took the jack apart. There was black enamel paint through the innards trapped in the power head seals. The black paint that the jack exterior was finished with was loose as hard black slivers inside the works. There was also dust or grit drawn in through the unprotected seal on the pump handle input power piston. The Harbor Feight jacks have as similar design. They don't have a rubber boot to keep dirt from being drawn inside.

Just taking my jack apart, cleaning up debris inside and assembling it brought it back to life. I cleaned the inside of the cylinder with 400 grit and jack oil. There was nothing broken or worn out. I cleaned all the o-rings with jack oil and paper towels. They weren't ruined, the were just dirty.

If you still have yours, you might be able to repair it.