# Altec truck engine revs up and down Why?



## Will I am (May 23, 2015)

1988 altec bucket truck engine speed goes up and down with pto on but no tools are on will not idle unless u turn pto off any ideas or literature on this ? Truck is a am550h


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## moondoggie (May 23, 2015)

Will I am said:


> 1988 altec bucket truck engine speed goes up and down with pto on but no tools are on will not idle unless u turn pto off any ideas or literature on this ? Truck is a am550h


Hydrolic pump engaging? I dont really know.


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## Will I am (May 23, 2015)

Pto is on when this is happening


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## kz1000 (May 23, 2015)

Gas engine?


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## Will I am (May 23, 2015)

Diesel


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## kz1000 (May 23, 2015)

I would look for a solenoid that is used to adjust low rpms to prevent stalling. Most vehicles have some form of anti-stall unit, whether vacuum or other.


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## Will I am (May 23, 2015)

This is the same problem I'm having 


bamf1luke said:


> Hello,
> I'm having an issue with my hydraulics on my hi ranger. the hydro pressure cylces up an down constantly which cause the engine to change rpms. It seem like the unloader valve may be worn out. I know the reason of the rpm change is because the pressure rises and moves the throttle clylinder(moving the throttle linkage). It acts like the pump is switching on and off(i know this isnt possible). The acummulator is charge correctly, pump will build good pressure, full on oil, not a filter or strainer problem.
> Is anyone familiar with a linesman 2, or a hydraulic problem like this? Any help will be appreciated! thanks


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## mauldinoutdoor (May 24, 2015)

Alot of bucket trucks have an idle control for on demand hydraulic pressure. My first truck had a hydraulic hose from the pump to the throttle with a actuator that open the throttle for higher revs to create more flow. My newer truck has an electric setup that is similar. And I have another truck that revs when the pto is on so it has to be disengaged to drive around the yard. Take a look near the throttle on the engine first for any actuators or solenoids that are loose or need attention, that would be my starting point


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## pro94lt (May 25, 2015)

I'm guessing it's the 8.2 Detroit?


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## Will I am (May 25, 2015)

Mine is hydraulic operated and problem has to do with controls


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## pro94lt (May 25, 2015)

What engine does it have? Detroit 8.2 cat 3308?


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## Will I am (May 25, 2015)

International or ford


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## Will I am (May 25, 2015)

This problem only exists when tools r off and pto is on u can see the hydraulic lines surging with motor speeds


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## Will I am (May 27, 2015)

Anyone know about them little spaghetti lines one is white other is orange and where they hook up ?


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## Will I am (Jun 5, 2015)

Anyone have a book on this truck?


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## johnyrtnow (Jan 26, 2022)

Will I am said:


> This is the
> 
> 
> Will I am said:
> ...


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