im trying to use this old harbor freight cherry picker to remove my engine but the dam thing wont go high enough. Its a stock height truck. When i jack it up it seems like it quits jackin way to early cuz i can lift the boom farther but then it drops back down. I know the jack was leaking a while ago but i think i fixed that so do i just need to add more fluid to it to make it go up farther. How do you do that?