# Dump Truck Hydraulic Question



## dean06919 (Jul 19, 2009)

I would like to get a little more lift from the hydraulic dump on my F350. Can I just replace the pump, or must I change the cylinder also?

My cylinder measures 20 inches long, is 4 inches wide, and the inner shaft is 1.5 inches wide. I'm not sure about the electric pump, since all the writing is worn off the tag. I believe it is a Monarch, it has the following numbers stamped on the side: G 10 01.

It currently dumps about 4 tons, anymore weight causes the wires going to my gas tank to burn the protective covering off.

All suggestions welcomed.


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## Rookie1 (Jul 20, 2009)

Go with a pto mounted pump or dont put so much in.


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## nickblaze466 (Jul 24, 2009)

you're just overloading the pump. easiest way to get more power for lift is to go with a bigger cylinder.


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## nvr-enuf (Jul 24, 2009)

*Go with the bigger cylinder*

I work in the hydraulics field and the cheapest & easist solution is to go with a bigger cylinder. 

Your lifting speed may take twice as long but the lift "power" will be twice as great. If that does not solve your issue you can then consider either an updated monarch pump / electric motor assembly that is meant for higher pressures and maybe puts out higher flow (check ebay, tons of them on there for around $250). 

Doing a PTO pump will be alot of work, been there done that before. The challege is typically dealing with the drive shaft if that is what you guys mean by a PTO pump.

Hopefully my advice helps


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## Blazin (Jul 24, 2009)

Sounds like your overloading the truck....and the pump! Time for a bigger rig


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## flxblx (Jul 24, 2009)

Make sure you have the correct gauge wire for this motor/pump unit, as well as a fuse or circuit breaker.

Larger gauge number means less current before smoking.

I am not familiar with the electric motor/ hydraulic pump setups. The ones I have nosed around used a starter motor. 

I may be wrong but; 12 gauge wire should have a maximum current of about 15 amps.

Also do not unload tail end of bed before raising. The load behind the pivot point will make the bed raise easier with less power requirement.

I do not intend to insult your intelligence, but I do not know how familiar you are with hydraulic hoists (dump beds) on trucks.


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## kevin j (Jul 24, 2009)

DC motor power units don't have a fixed gpm output like engine driven pumps. The motor rpm and therefore gpm drop off dramatically with increasing pressure load. There is a tradeoff with pump size for more flow or more pressure, but not both. (Unfortunately I am not aware of any DC power units with tiny two stage unloading pumps. There just isn't enough hp in these small units to make it work, but it is a nice dream.....)

as noted by others, to increase force you need to increase cylinder size or pressure or both.
Assuming the package was designed at maximum lifting for minimum cost, there may not be much extra in the design. then I would be concerned that upsizing the cylinder or pressure makes the next weakest link the frame or structural parts. 

let's take different tack: I would not try to increase capacity beyond its original design, only make sure it is back to the flow and pressure it was designed to do Possibly the relief valve in the unit is malfunctioned or set too low. Possibly the pump and cylinder were mismatched at some replacement time in the past.

If you are smoking wires or motor, then it is probably overloading the unit, or the wiring is too small.

I would install a pressure gauge in the cylinder closed end line, a voltmeter on the electrical terminal right into the motor, and an ammeter on the line to the motor.

See what the lift pressure, the voltage at the motor, and the current draw is when you are lifting. 

If pressure is low, then solving that could restore your lift power, NOT increase it from the original design, just get it back up to what it should be. I'd guess the rated pressure is pretty low with the cheap single acting type of cylinder and DC pump. This is not a commercial dump truck quality level I assume. So maybe somewhere around 1500 psi or less. 

If terminal voltage is too low, the wiring may be undersized and creating too much voltage drop. If amp draw is too high, the unit may be mismatched to the job.

Those are the cheap and easy things to check and to maybe fix.
Otherwise, maybe the whole truck/lift pump/hoist/brakes package is doing what it should do, it may just be too small for the loads you need to haul.

kcj


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## Patrick62 (Jul 25, 2009)

*Smokin'*

Re-reading the origional post, when the motor is pulling hard the wires going to the GAS TANK smoke... That tells me something that everyone else missed.

Voltage drop.

I am willin' to bet that this truck is setup just like mine is. And 4 tons sounds about right, in fact you probably have a ton on me....

The lift is HARD WIRED to the battery. Meaning there there is NO FUSE (it would blow anyway). Look it over, it should be running on a hunk of #2 welding cable minimum. Now, to get rid of the smoking wires run a GROUND WIRE from the battery to the FRAME! Might be tempted to run another ground wire from the lift motor to the frame as well. Bonus points if these are connected together with another piece of that #2 welding cable. Less resistance the better. The lift is going to pull crazy amperage during the first two feet, tapering off after that.

I have had enough GREEN wood on mine that it could not dump it. Way over what the truck is rated at. The unit works like a log splitter, and at some point the pressure is bypassed, probably 3500# or some such number.


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## KsWoodsMan (Jul 25, 2009)

A larger pump/motor will require larger wire and more current draw from your electrical system. Keep that in mind when retrofitting a bigger pump in your system. Will the altenator keep up with higher demands ? will you be able to install big enough wire to carry the larger pump ?

Larger wire in the first place is a good idea so there is less voltage drop (heat) in the wiring. Even if you continue to run your current pump the larger wiring is a good idea. That includes larger wire TO and FROM the pump motor. If it is grounded to the frame that wire from the pump to the frame should be large enough to carry the load. The body ground stap needs to be large enough from the frame/body to the battery to carry the load or it may smoke too. All the connections need to be clean and tight for good conductivity and no voltage drop (heat build up).

A larger cylinder will provide more lift with the same pump at the expence of slower lifting speed. It will require less amperage to operate so the motor brushes will last longer. Less amperage used means less heat in the wiring from voltage drop.

The tranny might not be setup for a bolt on PTO pump but that would sure negate the problem of smoking the wiring.

If I was having this problem, I would go for a larger cylinder and correct any wiring issues with wire better suited for the current load. I'd put up with slower lifting speeds. But only so it was easier on my system, not to increase the amount I could dump/haul on a fulltime basis. 

I'd probably still end up overloading it though. But thats just me.


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