many times the cylinders become stiff

from corrosion around the area that moves in & out

the pump has approx. 3600 psi running up

it has approx. 1800 psi running down

therefore the cylinders will extend but not retract

to check the condition of the cylinders

remove the 2 hoses at the pump

they are usually black and grey

you should be able to push the drive down

if the cylinders are not stiff from corrosion