Hydraulics stalling my truck when raising liftgate

[amanda11270]

Hello all, I have been on the forum here in the past with several tractors I have owned, but now I have an unusual issue with a truck of mine, and cannot seem to find a source online for trouble shooting my liftgate ao thought, why not the tractor forum, most tractors have hydraulics. It seems as though the hydraulics which I am not 100% familiar with (but im extremely mechanical) are having an issue. I use this 99 GMC 2500 truck for moving appliances as a contractor and in the recent past when just lifting the gate, sometimes the truck would shut off. It would restart, then the gate would continue to work. This happened a few times, I thought it was my AC running as it was hot both days I remember it. Well Sunday, I bought my boy a small gun safe for his birthday, and I picked it up with my liftgate truck, and the gate stalled the truck going up, then it would not move again at all. I mistakenly lowered it, and was then stuck with the gate down. Well after messing with it, it did raise again, but extremely slow. Now its stuck in the half way position, as soon as I push the up button the truck dies. Im thinking the electric pump is done, but not sure yet. I did jump out the contactor in the front of the truck, so its not the contactor that sends power from the battery. Its also not the switch because the pump mounted relay clicks when I push the up button, but again it just stalls the truck. Again im thinking the pump itself putting a big load on the truck, but could it be a hydraulic issue causing this im not aware of?

Thanks for any input.

 

[Industrial Toys]

I am not familiar with this stuff.

But, is it possible for you to raise the idle of the truck? Friends of mine up-fit trucks with all kinds of stuff and often, elevated idle schemes are part of this. An idling engine does not have much power.

 

[4570Man]

I used to have a box truck with a lift gate. It was powered by an electric pump which pulled off the truck battery. Is it possible the pump is shot and and is exceeding the amperage the battery can supply and the alternator is stalling the truck. If that theory proves to be wrong I’d need more information to come up with another one. That’s assuming it doesn’t have its own set if batteries like most bigger lift gates and doesn’t use a PTO off the truck transmission like my dump truck.

 

[oldnslo]

If this is a DC power unit the only load on the engine should be the load on the alternator.

Is it possible that you have an electrical issue with the lift killing the ignition system. Could be a challenge to find though

 

[100 td]

Just to clarify, you say "Hydraulics stalling my truck when raising liftgate" but then say "Im thinking the electric pump is done, but not sure yet"?
So is this an electric pump operated lift gate, or an electric solenoid controlled hydraulic gate running hydraulics from your steering or other pump?
If it's an electric pump, then look into your battery supplying the pump, I expect it is cactus. When the battery can't supply the rated current, it grabs what it can from the alternator, which "could" stall your truck.
A simple test it to get a known fully charged battery, disconnect the power supply to the pump and jumper to the known good battery, and test.
If it hydraulically operated, check your pump pressure and relief valve.

 

[bigdeano]

Check the voltage on the battery while using the pump. If it drops too low the engine won't run. Probably a weak battery like mentioned above.

 

[amanda11270]

My liftgate is an electric 12volt motor driven hydraulic pump that is mounted back inside of the liftgate itself. I brought this truck back to its former glory by replacing many body parts including the bed. So im real familiar with what runs the gate electrically. There is a contactor right off the battery that is operated by a switch inside the truck then from the contactor is a battery size cable going back to the gate assy that I would imagine does the heavy work to the motor. Im gonna charge my battery, I never thought it could be bad, however I dont drive this truck everyday so its possible. And the gate does put a load on it. Also its been real hot here in PA and its been my experience my batteries go bad when its either real hot or real cold.

Also my wife was giving the truck some gas when I got it to raise very very slowly to get us home. I thought it was a coincidence though as it did not work the first time we tried it.

 

[amanda11270]

If the battery was bad or going bad would it stall the truck though? Never has an issue starting the engine, unless the gate uses more CCA even with nothing on it.

 

[4570Man]

The gate is a lot longer load than a good starting truck. A not very good battery might start fine but not run the gate. Hook some jumper cables up and see if it still kills the truck.

 

[amanda11270]

I was thinking also my battery is only two years old, however I also added a plow to it this past winter to do my 1/4 mile driveway, and its 12volt hydraulic as well. All this probably took a toll on it, gonna investigate tomorrow. If its the battery I may have to buy another and maybe add a second to prolong their life