Dump truck hyd..help

Ok guys I get a call from my driver I left the bed take me hand off the lever and the bed comes down with out moving it to download position. ..I got check the truck thinking fluid is low or something nope fluid is good but bed easy back down everytime you left it ..I'm thinking the control inside the truck is bad but not sure ..it's 200 a lone but hate to buy it and it's not the problem. .anyone have any idea on what could be going on ..thanks

 

It's a single and no fluid coming out anywhere. .I had the cylinder repacked last year around this time..also when it goes up in notice the hose jumps a little like it's no fluid or something. .guess it's time for a new pump..any idea of the price of this things ..

 

Call the place that repack the cylinder was to that sounds like it's full of air..and needs to be bleed..so I'll try that tomorrow to late and dark tonight. .thanks guys I'll post back on what the problem is..

 

Yeah it's pushing the fluid back in the tank like it's in the down position

 

Guess I'm going to have to replace the pump...I took the controls line off and use my air compressor to left the bed and it still comes down so I know the controls are working the way they supposed to