How to Raise and Lower a WTJ-2 Truck Bed Jib Crane Boom

Which part of this crane actually decides whether the boom stays up? On the Vestil WTJ-2 vehicle-mounted cargo jib crane, the only model this article covers, it is the relief valve, not the handle and not your grip. Three terms carry the whole procedure. The relief valve is the small valve on the pump body that opens or closes the fluid's return path. The pump piston is the rod that extends a little with every stroke of the handle, pushing fluid into the lift cylinder. The telescoping boom is the sliding arm the load hangs from, pinned at a marked position to set its length.

Get the valve wrong and the rest of the routine buys nothing: strokes that build nothing, a boom that drifts instead of holding, a load that comes down at whatever rate the valve happens to sit at. For a dock door running lifts, that is dwell time and damaged freight, and both are decided before the first stroke rather than during the last one.

What Actually Moves the Boom Up and Down

A hydraulic cylinder holds a load for exactly one reason: the fluid inside it has nowhere to escape. That is the whole physical basis of this machine, and it is the reason the relief valve, not the handle, is the element that keeps a raised boom raised. Close the valve and the fluid is trapped, so the piston cannot retract, so the boom stays where the last stroke put it. Open it and the fluid has a path back, the piston retracts under the weight of the boom and its load, and the boom descends.

The handle sits upstream of all of that and only moves fluid one way. Which means the procedure is valve discipline first and muscle second, and it explains why the manual's lowering instructions never mention a separate down control, only the same valve opened a little. Operators who expect a lever with a return spring get a screw valve and a hand pump instead, and that mismatch is where most of the early confusion at a new dock comes from.

Close the Relief Valve Before the First Pump Stroke

Slide the notched end of the handle over the relief valve so the spring pin seats into the notches, then turn the valve clockwise, to the right, until tight. At that point the valve is closed, and only then does the handle go into the pump receiver for pumping.

The order is not a formality. An open valve gives the fluid a return path, so pumping against it cannot build the pressure that carries the boom; every stroke just circulates fluid back where it came from. Closing first is what makes the later strokes count, and it is the same closure that holds height between lifts. That ordering also explains a common misread on the floor: a crane whose boom does not respond feels like a failed pump, when the manual's sequence puts valve position at the front of the procedure.

Set Up the Handle, Then Pump the Raise

The pump handle comes out of its holder and gets used two ways. Grasp it by the black hand grip at one end; the other end carries rectangular notches that slide over the relief valve, which turns the handle into a wrench. Pull it off the valve, insert it into the pump receiver, and it becomes a pump lever worked up and down.

The notches and the spring pin are what stop the handle slipping off the valve while turning force is applied, which is the reason the procedure seats the handle before the turn rather than after. A handle that rides up mid-turn leaves you guessing at valve position, and an uncertain valve position is a boom that behaves differently on the next stroke than you planned.

Put in order, the raise runs: handle out of its holder, valve turned clockwise until tight, handle into the pump receiver, then up-and-down strokes, with the pump piston extending on each one and the boom rising as it does. Because each stroke adds fluid to the cylinder rather than repositioning the boom directly, height is built incrementally, many short strokes rather than one long pull, and the valve stays closed through all of it. There is no stroke count to memorize: the number depends on how high you are going and what is hanging on the hook. You quit pumping at the height the pick needs, and the closed valve does the holding from there.

Lowering Speed Comes From the Valve Opening

Lowering uses the same valve, turned the other way. Rotate it counterclockwise, to the left, with the end of the handle and the valve opens; the piston retracts and the boom comes down. The more the valve is turned, the more rapidly the boom lowers. Start by turning carefully until the boom just begins to lower, then turn farther to increase speed.

This comes down to flow restriction. The valve is the orifice and the load's own weight supplies the force, so what the operator controls is how far the valve is open. Picture a partly opened tap feeding a bucket: barely cracked, it trickles, and a little more and it runs. That image is an analogy, not a procedure, but it carries the control logic, small increments, watch the response, then adjust.

How You Know Each Step Took

Feedback on this crane is mechanical and immediate, and it arrives through your hands. With the valve closed, trapped fluid loads the handle on every stroke and the boom climbs with it, so the handle will tell you whether pressure is being held. A valve that never got closed gives you a stroke that swings through with nothing behind it. On the way down, the boom sits still until the valve passes the point where flow begins, and that first movement is your reference for just opened, the setting where the boom is barely cracked open and creeping.

From there the adjustment is small turns rather than big ones, following the manual's own pattern of turning until movement starts and then increasing from that point. Where the feedback on your unit is unclear, the WTJ-2 manual for that exact model is the reference to check rather than a check improvised at the dock.

Pin Position A and the 1,000 lb Rating

The telescoping boom fastens at the pin points the manual labels A and B. Pinned at point A the boom is short, and in that configuration the lifting capacity of the lifting bale is 1,000 lb (454 kg). Shortening the boom cuts the load moment that the structure and the vehicle mount have to carry, which is why the capacity figure is tied to a pin position rather than to the crane as a whole.

Read that number carefully before it goes into an internal spec sheet. The manual's page 2 and page 3 hook-capacity labels conflict, so the figure should not be carried over as a whole-crane rating or as the long-boom rating, and the installation itself still has to be confirmed with the vehicle OEM. A second pin position means a second configuration on the same machine, and a procurement decision built on a single number tends to assume the friendlier of the two.

When a Manual Hydraulic Boom Is the Wrong Choice

Every inch of lift on this crane is bought with handle strokes, and lowering speed depends on valve feel rather than on a control that returns to a fixed setting. That trade-off fits a dock door where lifts are occasional and one person works the handle. Suppose a warehouse is unloading trailers back to back for a full shift: the same plain mechanics that make the crane cheap to keep running turn into throughput loss, because lift time scales with height and with operator effort, and nothing in the design shortens it.

The buying questions that settle the fit are how many lifts per shift, what height range the work actually spans, and what the vehicle OEM permits for the mount.

If the job is high-cycle trailer unloading, all shift, every shift, this is not the tool, and the money belongs in powered lifting rather than in more pumping capacity. If it is a handful of lifts a shift at one dock position with one trained operator, the manual hydraulic boom earns its place, because the maintenance exposure is a valve and a piston rather than a power unit and the whole holding mechanism is visible at the valve.