Need help with dump truck hyd.

[afish]

OK I bought a GMC 91 k3500 dump for picking up material and moving my L39 around. It had some rust issues so I gutted it and getting ready to prep the back of the cab and the dump will not raise it worked fine and then one day no lift. I can here the solenoid clicking on the power unit and the dump tries to move. It stalled the truck. Does anyone have experience trouble shooting these 12v power units and pointers what I should look for. I am heading to the garage now to pull it off and see if I can find some manufacture info on it. I tried google but not much came up. It is seriously cold here but its in the garage so not sure if that could be the problem. I'm not real good with hydraulic's yet. Also it looks like there is ATF fluid in it instead of hyd'o fluid Is this common for these pumps???

 

[L-ENTERPRISES]

Clean your ground cable or replace it . Depends on the unit , but alot of them run ATF .

 

[PILOON]

Clean your ground cable or replace it . Depends on the unit , but alot of them run ATF .

ATF is in reality a hydraulic oil, and yes most probably the specified product for electro hydraulic pump.
Think of it, the pump and reservoir are outside of the heated engine compartement so that DC motor that spins the pump needs all the help it can get.

Even Fisher snow plows specify ATF as otherwise belts would slip trying to move the mollasis glob of gelled oil.

 

[Diamondpilot]

I am guessing its a 12 volt unit. It sounds like to me with the cold you may have a stuck pump due to water in the system. I would drain the entire system including the hoses and cylinder and warm things up with a heater. Clean it out and service with new fluid. Should be good to go. Like said before ATF is fine.

Chris

 

[afish]

Thanks guys I figured the ATF was ok but just wanted to make sure. I took a closer look at the unit and the only name I could find was on the breather cap it said Monarch. I jumped the solenoid and if keep the up button on the controller or keep the solenoid jumped it stalls the trucks engine. The motor will not run on the power unit so sounds like froze up motor. I think I will just buy a hole new unit for 300-400 bucks instead of spending 200 to fix this one and possibly have problems down the road. Any recommendations on a good STRONG unit/BRAND and where is a good place to get it.

 

[Diamondpilot]

You have not answered us if this is a electric unit or a engine driven unit/pto off the tranny? Why is it stalling the trucks engine? I still feel this should be a easy fix and either way since its a used truck you need to drain the system and get fresh fluid in.

I am guessing its electric since you talk about a solenoid and 12 volt.

Chris

 

[kennyd]

You have not answered us if this is a electric unit or a engine driven unit/pto off the tranny? Why is it stalling the trucks engine? I still feel this should be a easy fix and either way since its a used truck you need to drain the system and get fresh fluid in.

I am guessing its electric since you talk about a solenoid and 12 volt.

Chris

I think he did answer this quite clearly by saying:

I jumped the solenoid and if keep the up button on the controller or keep the solenoid jumped it stalls the trucks engine. The motor will not run on the power unit so sounds like froze up motor.

The engine is stalling due to the excess amount of current the motor is drawing.

I would do 2 things before replacing everything:
1) Change your fluid. It may be contaminated with water and frozen.
2) Take the motor to a starter/alternator shop and get it tested-it's basically just a starter motor anyway so the should be able to help you.

 

[afish]

Sorry if I wasn't more clear yes it is a 12v unit not a pto. I'm not exactly sure why its stalling the trucks engine other than it seems like since the hydraulic units motor isn't turning its putting such a large load on the battery and alternator its causing the trucks engine to stall. It has a brand new battery in it, also the ground seems to be good.

 

[Builder]

Monarch makes a ton of these electric motors. I had a few of them on dumps and a few that went under the hood to power front hydraulics for dumptruck plows. The parts are easy & plentiful.

 

[wushaw]

Monarch make a good unit. If you just want to replace it, check out Ebay.