I just installed new main hyd pump on tractor. It has full hyd pressure at low idle. The engine is under a load and want spin tires until it getting to traveling then it has full power. The new pump is not destroking. It was not same pump as original and has no pressure setting on pump itself. But it hooked up the same and has very good pressure but it has it all the time. It is basically like starting a truck to moving in high gear. At low idle just raising blade to fast will almost choke engine down. Any ideas would be appreaciated. The parts store was closed for weekend by time i got pump on and no one there to ask till monday and i would rest better if i could solve this sooner. Thanks to anyone with some answers.
Does it have a electric solenoid on the side? Scott S
No sir only has gravity feed suction pipe, pressure line, one small line that runs to a pressure check block , a case drain line and one more 3/8 line that is the activation line i quess. To be honest the replacement pump from pioneer (our local dealer) was $2000 more than this pump, with diffence being it was pre-set, with no presure regulator on pump, and a few lines hooked up in differnt spots on new pump. The new pump is super strong but it just stays that way at all times.
Are you sure that you have a pressure compensted pump, or a full flow pump that has pressure controlled by a relief valve somewhere else in the circuit. A normal pressure compensated variable displacement pump will have two pressure settings, the residual or standby pressure somewhere around 250 PSI, the other would be compensated pressure which would be set to machine specs example 3000 PSI. When this type pump starts up the swash plate is spring loaded to full stroke and almost instantaiously rises to residual pressure which over comes the spring and destrokes the pump and will maintain the residual pressure. Once that you operate a function, the residual pressure is blocked from the stroking piston and the spring will stroke the pump to full flow. As pressure builds it is felt behind the stroking piston spring and starts to destroke the pump as the pressure rises, when the system attains max pressure the pump will destroke and maintain that pressure at minimum flow until the pressure drops off, then as resistance to flow decreases the pressure behind the stroking piston spring the pump increases stroke and flow. Unless you have a remote residual/compensator control to control the pump, it will go to full stroke on start up and stay there. At that point you need to find out what the pump specs are. it may be set up to run something like a chipper that requires full flow all the time and has a relief valve in the control valve to regulate pressure.
You obviously know a great deal about these pumps. I waited until i talked to the salesman at loggers hydraulics( a great place to buy pumps for anything) where i purchased pump befor i replyed. He tells me exact same thing, that when a control on machine is used then pump begins to flow, when no control is used pump goes back to a neutral (no pressure) position. He told me how to troubleshoot by cranking machine and moving control flow line , if it is stiff (under pressure) the valve on tractor is stuck open. He then said to remove line, cap it and test that pump is destroking. If it does then i've got to find the control valve on machine and unstick, adjust or replace. Thanks for the help i was given and if you know anything about the pump activation valve on a 950 CTR that would great.
oldseabee, i have narrowed problem down some. It seems to be a valve in the bank thats not shutting off and pump thinks it is supposed to be pumping oil. It is a spare tractor we use in land clearing, pulling a firebreak plow, a chopper and dirt pans so we are not it using much right now due to the rain, so i work on it when i catch a break. Sat i cranked it , ate lunch and checked which valve got hot the fastest, well i waited too long the entire bank was well over 100 degrees in a very short time. so i going back today with new batteries in lasertemp and watch it close. Just wanted to update you sir!!!
Did you mean on the by-pass valve right behind hyd filter? Yes there is an electric solenoid there