I. How to Repair a Manual Forklift That Won't Lift
Check Hydraulic Oil Level
The first step is to check the hydraulic oil level in the tank. Locate the tank cap or sight glass and ensure the oil level reaches the specified mark. Insufficient oil will prevent the system from building up sufficient pressure. If the oil level is low, slowly add dedicated manual forklift hydraulic oil to the specified level. Never use substitutes such as engine oil or brake fluid, as this will damage the seals. After adding oil, perform several unloaded lifting and lowering operations to purge any air that may have entered the forklift.
Check for Overloading
Confirm that the weight of the load does not exceed the forklift's rated load. Overloading will directly cause insufficient hydraulic system pressure, preventing lifting. The solution is clear: immediately unload the overloaded load. Before operation, always know the forklift's maximum load capacity to avoid equipment damage or safety accidents caused by overloading.
Check for Air in the Hydraulic System and Perform a Bleeding Operation
Air mixed in with the hydraulic oil will create air resistance, manifesting as a light or weak feeling when pressing the handle, or slow or vibrating forks. The air purging method is as follows: Open the oil tank cap or filler plug (not fully tighten), and repeatedly and quickly press the handle to perform dozens of no-load lifting operations, forcing air bubbles to escape from the filler port. After observing that no more air bubbles emerge from the oil, tighten the filler port.
Check the Hydraulic Pump
If the oil level is sufficient, there is no overload, and the pump still cannot rise after purging the air, the hydraulic pump needs to be checked. Common problems include worn, aged, or damaged main seals (such as U-rings) inside the pump, leading to internal leakage and preventing pressure build-up. Troubleshooting requires disassembling the pump body to inspect the seals. If damage is found, a hydraulic pump seal repair kit specifically for this forklift model must be used. During installation, pay attention to the seal orientation and ensure adequate lubrication.
Check Hydraulic Oil Contamination
Using the wrong type of oil or severely contaminated hydraulic oil (turbid, containing impurities, emulsified) will accelerate seal aging, clog oil passages, or affect oil flow. Check the oil color and condition. If the oil is incorrect or severely contaminated, the old oil must be completely drained, the oil tank and related oil passages cleaned, and then a sufficient amount of the correct type of hydraulic oil added.
Check for obstructions in the forks or chain
Mechanical obstruction can also hinder lifting. Check the lifting rails, both sides of the lifting chain, and its sprockets for tangled packaging tape, ropes, debris, or hard objects that may be stuck, or for twisted or dislodged chains. Remove all visible foreign objects and ensure the chain runs smoothly on the sprockets without skipping teeth. If the chain is too loose or too tight, adjust the tension according to the instruction manual.
II. What to do if a manual forklift won't lower
Inspect the unloading valve (control handle) and linkage mechanism for malfunctions
This is the most common reason why the forks cannot be lowered. The unloading valve is usually located at the base of the handle and is controlled by a lever, knob, or button. Check if there is any sticking, insufficient travel, or no response when operating the unloading valve. Try operating the unloading valve forcefully several times while simultaneously pressing down the handle. If this is ineffective, the unloading valve needs to be disassembled: check if the valve stem is bent or rusted, if the internal spring is broken, if the seal is bulging and stuck, or if the valve core is clogged with dirt. Clean the valve core and valve chamber, replace damaged springs or seals (oil-resistant fluoropolymer rings must be used), and reinstall after ensuring the valve stem moves freely.
Check hydraulic oil level
While insufficient oil mainly affects lifting, extreme oil shortage can also affect the lowering function (poor oil return from the cylinder). Check the oil level as described above; add oil to the specified level if insufficient. However, this situation is rare, and the unloading valve should be checked first.
Check for improper adjustment or deformation of the push rod/connecting rod
If the push rod or connecting rod mechanism connecting the unloading valve to the internal valve core is bent, deformed, or the fixing screws are loose, or improperly adjusted, the unloading valve's action will not be effectively transmitted. Check the connecting rod for visible bending and loose connections. Try recalibrating or straightening the connecting rod, tighten loose connections, and ensure that the unloading valve can accurately and fully open the internal pressure relief channel.
Check for mechanical jamming
After ruling out hydraulic system causes, the mechanical parts need to be checked. Observe whether there is friction interference between the forks and the mast or vehicle body when the forks are lowered (possibly due to fork deformation). Check the lifting chains on both sides for twisting, severe corrosion, or excessive tension that could cause the sprockets to become stuck. Check the forklift track for any obstructions or deformation. Remove any foreign objects, correct any deformed parts, lubricate the chain and track, and adjust the chain to the appropriate tension.
