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brewcrew

Live pto on trucks

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I have an international 2574 silage truck with a live pto, driven off the front of the crankshaft. It has an electric switch to turn the box on/off. But sometimes the box will run while shut off, usually at higher rpm. Where should I start looking? The solenoid? The valve? It’s causing my endgate to come unlatched. It doesn’t move under load, only while empty. Thanks for any advice!

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Here is a pic of my hydraulic setup if that will help

F83B7DFB-FA75-4BAF-AE98-8EE13CA12F8D.jpeg

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The oil is getting back to the motor. I would look at valve first. Sounds like the valve isnt closing. Maybe a blown o ring in it.

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Pull solenoid/switch  & clean....

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Its hard to tell from the pic, but that almost looks like a "dump valve" setup---where the valve does not block flow to the orbit motor, but simply dumps the pressure (and flow) to tank when off.   If so, you may have a blockage in the dump valve or flow control, or maybe even in the filter, that is restricting oil flow to tank, and creating enough pressure in the system the motor will run when there is no load (empty). 

To figure out if its electrical or hydraulic, check the voltage at the valve coil across the two pins (looks like 1/4" blades in your pic).   Depending on operation (NO/NC) you should have full 12V when the electric switch is one way, 0 V when its the other way.  (My guess is it will be 12V when ON).  If not,  troubleshoot the wiring or switch.  If the voltage switches properly, then its a hydraulic issue, check the valve spool, etc.

Its entirely possible with a setup like this, that even if everything is working properly, there are enough restrictions in the valves that enough oil flow can still travel thru the orbit motor  to make it turn unloaded.   Or if you installed a bigger pump recently, etc.   You may need to insert a NC valve into the line going to the motor so it blocks it when your switch is off.   Just make sure its AFTER the pressure relief valve on the pump, not before (DO NOT ASK ME HOW I KNOW THIS...)

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