My 1995 F450 dump truck-dump goes up, won't go down

[Phillip38]

Is the Hydraulic pump electrical? The PTO has a lever that has UP or Down, is connected to the pump with a wire cable, in the center is a smaller white insulated wire, I think that would indicate that the hydraulic pump is electrically controlled. Do I need a new control cable? How do I get the dump to go down, can I un screw one
of the hydraulic hoses at the pump-will this allow the dump to come down, do I need a new pump-what is going on? Just know how to use the dump truck.

 

[RustyA]

If it will go up with engine off and stationary it for sure is electric pump. Usually 12 volt pumps reverse polarity for in and out movement similar to a power window. Perhaps the switch is faulty and not reversing the pump?

 

[dirttoys]

Is the Hydraulic pump electrical? The PTO has a lever that has UP or Down, is connected to the pump with a wire cable, in the center is a smaller white insulated wire, I think that would indicate that the hydraulic pump is electrically controlled. Do I need a new control cable? How do I get the dump to go down, can I un screw one
of the hydraulic hoses at the pump-will this allow the dump to come down, do I need a new pump-what is going on? Just know how to use the dump truck.

Don't know your truck. Most of the electric as mentioned above reverse polarity. Normally if they go one way and not the other it is a relay.

Best,

ed

 

[4570Man]

If you have a pto button the pump probably isn’t electric. When operating the bed do you hear a whining noise? The electric pumps are fairly loud where a pto pump is quite. Is there an actual value under the truck? unscrewing a hydraulic line would succeed in getting the bed down but I’d highly recommend not doing that.

 

[cwbyeng1300]

If it is an engine driven PTO it is probably power up, gravity down. For some reason the valve isn't opening to let the fluid flow back from the cylinder. Coul be electric solenoid, stuck mechanical valve, bad relat, etc.

 

[4570Man]

If it is an engine driven PTO it is probably power up, gravity down. For some reason the valve isn't opening to let the fluid flow back from the cylinder. Coul be electric solenoid, stuck mechanical valve, bad relat, etc.

That’s my guess. We really need more details on how the dump works to come up with a solution.

 

[Phillip38]

Thanks for all the advice. The PTO is on the driver side, and pulls up to engage the pump. First, the dump would not work at all, then I got under the truck and
discovered that the UP/Down cable was against the manifold, and the cable had been slightly burnt. The cable is a multi-wire type cable with a white insulated smaller wire in the center of the cable. This cable is connected to the pump.
After taking off the burnt cable insulation, and carefully looking at the cable, I tried the up and down device-this time the dump went up but would not not go down, tried several times. Do I need a new up/down control cable, the hot manifold may have damaged the control cable, is this cable a DC hot electrical wire to the pump.
I am calling this cable a CONTROL DUMP UP/DOWN CABLE, perhaps I am not calling it the correct name.

 

[Phillip38]

R, you called the up/down device a SWITCH, does this switch allow the pump to engage, the device/SWITCH has a lever, and on the plate below an UP or DOWN POSITIONS, with the lever forward the dump goes UP, with the lever backward, the dump goes DOWN. Makes sense-SWITCH.

 

[bcp]

You broke the law!

"What goes up, MUST come down."

I think if you get it down before the law finds out, you will be OK.



Bruce

 

[jigs_n_fixtures]

Most dump truck have single acting hydraulic cylinders. The pump fills the cylinder, through a one way valve, raising the bad. There is typically a valve to drop the bed which allows the hydraulic fluid to bypass teh one way valve and flow out of the cylinder, and back into the reservoir.

Are you sure it is PTO operated? There are a lot of different ways to make it work, depending on what else is on the truck. I’ve sent a few of them: air over oil, on truck with air brakes; an electric lay driven hydraulic pump, a hydraulic pump belt driven with an electric clutch. PTO driven pump with an electric clutch.

Pictures would help a lot.