My 90ish 40ha ford dual fuel standard controls lift has had different issues since I adopted her.. She's always been sluggish and jumpy in drive / rev, she's blown her fair share of cylinder seals and rotted hoses, she's been neglected, and on and on.. Last year I loaned her to a neighbor and something happened where none of the hydraulics would respond due to apparent low pressure. ? is when and by what is the dump valve activated? Is the dump valve dead until a ground function or platform foot pedal is activated? There's more to this but I want to know how the valve is "suppose" to operate first. Thanks, AND JLG schematics are horrible......... to say the least..
Sorry JLG
Yes, the dump valves activate hydraulic functions 1 - on ground control, all the time 2 - on basket, when the foot switch is down. They are powered by 12 volt relays inside the main electrical panel. Those relays are a common source of trouble.
Thank you.. "1 - on ground control, all the time " So when on ground control the dump valve is "always" hot 12V? Reason is someone had a jumper wire on the BB dump relay to make it hot all the time. My small motor driven pump would get so hot I couldn't touch it. I removed the jumper and now the dump is only active when I select a function from ground or depress the foot switch on platform. Now the pump stays just warm.
The Aux. pump was on all the time? Something wrong there. The Aux. pump should only be on when the Aux. pump toggle switch is activated. Sounds like someone was using Aux. function to power the dump valve circuit. Something sticks in my mind about the Aux pump on those 40HA's. There's a solenoid on the side of the box that powers the Aux. pump. It looks like a normal 12V solenoid, but it's not. It's actually one for a snow plow/power tailgate. It's configuration is backwards from normal. You put the wrong one on, and the pump runs all the time. Can't remember exactly, it's been 15+ years.
No sorry the work pump was building pressure all the time due to the dump valve was always active. Not the aux pump. It works thru the toggle. Also what is a adlow relay mounted to back of ground box by governor controller? Thanks