1998 gradall excavator xl 4100 hydraulics not working

Was wondering if anyone seen this problem? The engine in the upper deck idles up but I dont have any of the hydraulics working and the gradall will not move either from the upper deck motor. The gradall will drive from the lower engine but when you are going to work from the top engine the hydraulics will not function. I changed the hydraulic filters and still nothing. The pump drive that mounts behind upper deck engine has been replaced and still nothing. This pump drive was replaced because it was all messed up when it was removed to inspect. This is were the pumps get their pressure from the pump drive engaged with the flywheel but still no change in the hydraulics. Anyone worked on these gradalls?:Banghead

Do you have pilot pressure?

Is the pilot solenoid being activated?

Has someone had their fingers in the pump and have the stand by pressure backed off?

The is probably more, but that is a start.

No pressure at pilot controls. When I put the arm rest down that should energize I believe the monitor so the hydraulics will work. Anyone know where the wires to the switch run to under the arm rest.

Right behind the operators cab in the compartment for the control valves is the solenoid valve for the pilot I would check there first they have been known to corrode and stop working that shuts everything off. It is actually mounted right on the panel which is closest to the back of the cab.

Going to try and find this solenoid valve for the pilot in the parts book so I can find it. How will I know which one it is if there are more than one that look the same. Is this where one of the wires from the switch under the arm rest goes to when the arm rest is down to energize system?

Found the compartment behind upper cab were the valves are. Is the solenoid pilot valve the one mounted on the wall behind cab have two spades were the wires go into. Looks like a filter is next to it also.Is one wire ground and is the other hot when activated from arm rest? Also how many ohms should I have if this solenoid is good. How can I check pilot pressure.

Gradall offers free access to their manuals through their website. Sounds like you need to go to their website, find the manual look up p, and get a manual

Yes that is the one I didn't tell you this but you can pull it out and put a plug in the hole to test and see if the machine works BUT the controls will be live ALL the time!

Update changed out the pilot solenoid behind cab and now hydraulics work. Thanks dirthog and all.

Hi,

Can i get some pro's and cons of the Gradall Excavators

Thanks In Advance