# 12 Volt hydraulic pump question



## Countrybumpkin (May 12, 2002)

Just bought a used dump trailer...I know it needs a new battery, but the problem is, I charge the old battery up, hit the toggle switch up, she goes up, but it doesn't like going back down. This a power up only pump, but has that electromagnetic solenoid on the pump that allows it to go down when you hit the down switch. I hear it click, the bed starts going down, then slows to a stop before half way down. I can hear the solenoid clicking, but she won't move. Wouldn't think it would be a low voltage issue w/ the battery, since it goes up...doesn't appear to be wedging itself on anything either. Any ideas here? It does go down REAL slow when she does go down that little bit...thought it should drop faster than she does, but never messed with pumps like these!


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## agmantoo (May 23, 2003)

Often a hydraulic system will have either an adjustable or a fixed orifice in the line that bleeds off the pressure/fluid to the storage reservoir. This orifice allows a controlled descend and not a rapid drop. In some circuits the size of the return line will accomplish the control. Observe the plumbing of the cylinder to attempt to determine if you have an adjustment or a component in the circuit that is not understood and investigate same. Trash in the control valve itself will clog its port and create an erratic flow. Be very careful as you work on this as the bed can suddenly drop and injure you. It is best to secure the bed to something over head that can support the bed in event it drops. PS...some hydraulic cylinders have such an adjustment made in them near the port they control.


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## Beeman (Dec 29, 2002)

Countrybumpkin said:


> Just bought a used dump trailer...I know it needs a new battery, but the problem is, I charge the old battery up, hit the toggle switch up, she goes up, but it doesn't like going back down. This a power up only pump, but has that electromagnetic solenoid on the pump that allows it to go down when you hit the down switch. I hear it click, the bed starts going down, then slows to a stop before half way down. I can hear the solenoid clicking, but she won't move. Wouldn't think it would be a low voltage issue w/ the battery, since it goes up...doesn't appear to be wedging itself on anything either. Any ideas here? It does go down REAL slow when she does go down that little bit...thought it should drop faster than she does, but never messed with pumps like these!


 The dump trailer I use and have worked on works just like you describe, it lowers at an even rate and fairly quickly. Measure the voltage at the solenoid and the ground of the solenoid. possibly a bad ground causing a low voltage not opening solenoid all of the way. Then of course the possibility of a blockage caused by trash or a restricted hose slowing it down.


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## rambler (Jan 20, 2004)

How cold is the weather by you? Will probably be much different in 90 degree summertime....

--->Paul


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## DaleK (Sep 23, 2004)

Good ideas so far. Something else simple... I hope they have a filter plumbed into it? Neighbour had the same problem with a trailer of his, tried everything with the solenoid, valves. They had the filter plumbed into the return line before the reservoir.... plugged full.


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## Countrybumpkin (May 12, 2002)

Thanks all! there is no filter on it, should put one on it! Found the adj. screw on the pump...no difference when turned. So, I took the hose off, will replace-not looking good on the outside anyway-but when I drained the oil, was pretty thick. Not certain what they were using for fluid, but am going to try a lighter weight in it and see if it helps any!


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## agmantoo (May 23, 2003)

The adjustment on the pump is probably the bypass valve for pressure relief on the up stroke. Maybe should leave it alone! The down stroke oil should bypass the pump IMO.


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