Rebuilding a floor jack, Craftsman 50145, ran into a problem

[i6pwr]

I've owned this jack for about 20 years, Sears 3 1/2 ton, been great but started to slowly leak down and it lost the initial rapid pump. I bought the seal kit from lazzar and I didn't mess with the 'Do not Adjust" screw, but I did replace all the seals in the main piston, jacking piston, the screw that turns to lower and stop the flow of fluid, along with the two check balls in which I did replace in the correct order. I replaced what the red arrows point to, as well as the O rings in the main piston and the large blue seal and is oriented correctly.

I believe the parts layout was used in the Garage Journal so not mine, except the additional text.

My problem is I get the quick rapid pump, but then it doesn't transition to the second stage and even trying to lift a person it takes a good bit of effort to pump the handle. Would this point to the two check balls or another area?

 

[ajchien]

The two do not adjust valves are the spring loaded valves.

I can’t 100% tell which valve is which based on the picture but the one with the lighter duty spring will be your “quick lift bypass”. When your jack encounters a load and pressure increases, it opens and shifts the oil flow to the “second stage” of lifting. The one with the heavier duty spring is your “safety valve”. If the pressure exceeds the equivalent of the jack capacity of 3.5T, it will open and stop the jack from lifting. My best guess is that the cone shaped valve will be the one with the weaker spring and the ball valve will have the stronger spring.

If your quick lift valve is too tight, you won’t transition to the second stage and risk blowing the quick lift seal. If it’s too loose, you lose the quick lift. If your safety valve is too tight, you’ll lift more that the rated capacity of the jack risking blown seals or bent metal. If it’s too loose, you won’t be able to lift the full jack capacity.

Hope that helps.