Before You Install — Know Your Circuit Type

KTI DC power units come in four circuit configurations. Installing the hydraulic lines differently depending on which you have:

Tools and Materials Needed

• Two 3/8-16 mounting bolts (3/4" length) and appropriate lock washers or Nyloc nuts
• AW32 (cold climates, below 32°F) or AW46 hydraulic oil — do not use motor oil or ATF
• Battery cables: 2 AWG for runs under 4 feet; heavier gauge (1/0 or 2/0) for longer runs — see cable gauge table below
• Hydraulic hose and SAE ORB fittings appropriate for your port size
• 5/16" eyes or ring terminals on battery cables
• Torque wrench (for battery terminal nut and hydraulic fittings)
• Wrenches and socket set

Battery Cable Gauge by Run Length

Undersized battery cables cause voltage drop, which makes the motor draw more amps, runs hotter, and degrades solenoids and motor windings. This is one of the most common causes of KTI pump failure on new installations.

Step-by-Step Installation

Step 1 — Mount the Power Unit

1. Position the Pump

   Mount the pump using two 3/8-16 x 3/4" bolts through the mounting holes on the motor/pump body. The reservoir breather cap must be accessible and should not be obstructed by the mounting position or the trailer bed. The pump can be mounted on the trailer tongue, inside a toolbox, or directly on the frame — as long as the reservoir can be filled and checked without removing the pump.

2. Orient Correctly

   The pump must be mounted in the orientation shown in the KTI diagram — the reservoir must be upright (not tilted more than 15–20 degrees). A tilted pump causes air pockets in the reservoir that contribute to aeration problems. The motor can face any direction, but the reservoir and pump body should be as close to level as possible.

Step 2 — Connect Hydraulic Lines

1. Single-Acting Circuits — One Line

   Install a 9/16-18 SAE ORB (#6) hydraulic fitting into the "P" port. Torque to 18 ft-lbs. Connect the hydraulic line from the base (bottom) of the cylinder to this port. The "P" port is the only hydraulic connection on a single-acting pump. Gravity returns the fluid to the reservoir when the bed drops.

2. Double-Acting Circuits — Two Lines

   Connect the "A" TOP port to the base (bottom) of the cylinder — this is the port that raises the bed. Connect the "B" BOTTOM port to the rod end (top) of the cylinder — this is the port that lowers the bed under power. Getting these reversed will make the bed lower when you press raise and raise when you press lower.

3. Dual Double-Acting — Four Lines

   For two-cylinder systems: "A" port (UP) → base of the first cylinder; "B" port (DOWN) → rod end of the first cylinder; "A1" port (OUT) → base of the second cylinder; "B1" port (IN) → rod end of the second cylinder. Verify which cylinder is which before connecting — refer to your trailer's hydraulic schematic.

4. Check All Fitting Torques

   Tighten all hydraulic fittings per KTI's torque specs. SAE ORB fittings: seat the O-ring by hand until it contacts the face, then torque per size — #6 fittings to approximately 18 ft-lbs. Do not overtighten — cracked manifold ports are a common result of excessive torque on aluminum manifolds.

Step 3 — Fill the Reservoir

1. Fill With the Cylinder Fully Retracted

   Before filling, confirm the dump cylinder is fully retracted (bed fully down). Filling with the cylinder extended means the system will be overfilled — when the cylinder retracts, it pushes fluid back into a full reservoir and causes overflow. Remove the breather cap/dipstick and fill with hydraulic fluid.

2. Fill to the Correct Level

   Fill to approximately 1 inch from the top of the reservoir. Most KTI reservoirs have a "Full Line" marked on the side — fill to this line. Do not overfill — the fluid level will drop slightly when the cylinder extends on first use, and air bubbles during the bleed cycle can push fluid out of the breather if the reservoir is overfull.

3. Use the Correct Fluid — Do Not Mix

   KTI recommends premium AW-grade hydraulic oil: AW32 for cold climates (operating temperatures below 32°F) or AW46 for most applications. Premium brands: Chevron Rando HDZ, Mobil DTE 10 or DTE 20 series, Shell Tellus, AMSOIL. Dextron III ATF is acceptable as a substitute under normal conditions. Never mix hydraulic fluid types — incompatible fluids can gel or lose viscosity. Never use biodegradable hydraulic fluid with standard Buna seals (Viton seals are required for biodegradable fluids — they are optional and must be specified at ordering).

Step 4 — Connect Electrical

1. Connect Battery Ground to the Motor

   Connect the ground (negative) battery cable to the ground terminal on the DC motor body. This is a dedicated terminal on the motor — not the trailer frame. The power unit must be grounded directly to the battery negative terminal. A poor ground causes the motor to run hot, draws higher amps, and is the root cause of most hydraulic system electrical problems including solenoid failure and motor winding damage.

2. Connect Positive to the Start Solenoid

   Connect the positive (red) battery cable to the start solenoid. The start solenoid is the large relay-style component mounted next to or on the pump body. Connect to the terminal that is connected to the main positive battery cable. Torque the battery terminal nut: hold the bottom nut in place with one wrench while torquing the top nut to 3 ft-lbs with a second wrench. This two-wrench method prevents twisting the solenoid terminal stud, which is a common cause of solenoid failure.

3. Connect the Remote Pendant

   Reconnect the 2-button (or 3/4-button) wired remote pendant to the quick-disconnect port on the pump. This will be your test tool during the bleed cycle. If you're installing a KWR wireless system, connect the pendant to the KWR receiver's receptacle port and connect the KWR's HPU connector to the pump — see the KWR installation guide.

Step 5 — The Bleed Cycle (Critical — Do Not Skip)

Air trapped in the hydraulic system causes erratic bed movement, foamy fluid, fluid overflow, and sluggish performance. The bleed cycle purges all air before full operation. It must be performed on every new installation and after any hydraulic line disconnection.

Remove the breather cap/dipstick before starting — leave it off the entire time. You need to be able to see the fluid and spot air bubbles returning to the reservoir.

1. Raise to 1/3 — Watch for Air Bubbles

   Press the UP button on the wired pendant and raise the bed one-third of the way up. While raising, watch the fluid through the open breather cap opening. You may see fluid returning to the tank and air bubbles rising. If you see air pockets or aeration (foamy, bubbling fluid), stop immediately — let the fluid settle for 30–60 seconds before continuing. Do not let the fluid level drop below half-full during this step. If it drops below half, stop, lower the bed, and refill before continuing.

2. Lower to Full Down

   Press the DOWN button and lower the bed back to the fully seated position. On single-acting pumps: activate the gravity-down function or open the solenoid — the bed drops by gravity. On double-acting pumps: press Power Down. Watch the fluid level as the cylinder retracts — fluid returns to the reservoir and the level will rise. This is normal.

3. Raise to 2/3 — Check Fluid Level Again

   Press UP and raise the bed two-thirds of the way up. Again watch for air bubbles in the breather opening. Stop if significant bubbling occurs — let it settle. Check that the fluid level has not dropped below half-full. Lower completely back down.

4. Raise to Full Stroke — Lower Completely

   Press UP and raise the bed to the full up position. Watch for air. Lower completely. After lowering, refill the reservoir to the Full Line if the level has dropped. Replace the breather cap.

5. Repeat If Needed

   If you still see air bubbling or the bed movement is jerky or inconsistent after completing the three-step cycle once, repeat the entire cycle. Some installations require two or three complete cycles to fully purge all air, particularly on longer hydraulic line runs.

Post-Installation Checks

• Check all hydraulic fittings for leaks after the first 5–10 cycles — tighten as needed
• Check the fluid level after the first work day and top off if necessary
• Verify the remote pendant and wireless controller (if installed) operate all functions correctly
• Inspect battery cable connections for tightness — vibration can loosen terminals over the first few days of operation
• Check that the breather cap is reinstalled — operating without it allows debris and moisture into the reservoir

Frequently Asked Questions