Just don't get it. About an hour into a job my lift hydraulics just stop working. I let it cool down and everything works fine. The oil appears clean, the filter isn't clogged, all the functions work, the lift is level. So frustrating. Any ideas? Is there a temperature sensor for the hydraulic system that may be wacky? The 1999 gas engine with 3000 hours runs fine. As I write this, I think I should hook up a pressure gauge to the system when it stops working. Would that tell me if my main pump is going out?
Are you losing only one, some or all functions? Which ones?
All. Not slow or any stutter. Just zero. As though someone had turned off a switch. Occasionally, when out of level I will lose or slow down some functions but not like this.
That doesn't scream pump failure to me. Usually a weak pump will gradually lose performance as the oil heats and thins. It won't be a sudden 100% loss. If you haven't already, head to JLG's website. There should be service manuals and electrical/hydraulic schematics available for free download. I'd start by reading the schematic. Start at the pumps and work your way thru the hydraulic system, identifying components or valves that could cause the symptoms you're having. You may even discover its an electrical issue causing a solenoid to not function.
Thank you. I will check back with you.