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Common Faults and Troubleshooting of Forklifts
Aug 09 , 2022
For the common faults and troubleshooting of forklift trucks, we start with the analysis of the various systems of the forklift truck. The following are the common faults and troubleshooting methods of the various systems of the forklift truck.
1. Forklift electrical system:
1. Inserting the key cannot start, check and repair or directly replace the forklift connector;
2. If the light is not on, check and repair or replace the switch, fuse and light bulb;
3. If the horn does not sound, check and repair or directly replace the fuse, switch and horn;
4. The power indicator is not displayed, check and repair or directly replace the fuse, key switch, power indicator;
5. The pump contactor is not working, check or repair or replace the micro switch and pump contactor
6. The pump motor does not work check and or replace the fuse, pump contactor, and repair the motor;
7. The steering contactor is not working, check or repair or replace the steering switch and contactor;
8. The steering motor does not work check or repair or replace the fuse, contactor, steering motor;
9. The walking contactor does not work, check or repair or replace the contactor and circuit board;
10. The travel motor does not work; check or repair or replace the fuse, contactor, circuit board, motor
11. The travel motor fails to rotate at high speed, check or repair or replace the circuit board.
2. Forklift engine system:
1. The speed of the engine is low - the battery of the forklift is low, and the battery can be charged directly;
2. The speed of the engine is low - the circuit connection is poor - check whether the wire is loose;
3. The speed of the engine is low - the starter is faulty, whether the contact between the motor brush and the commutator is poor, and whether the internal wiring head of the starter is poorly connected;
4. The oil pressure is too high and the quality of the lubricating oil is poor - when the viscosity of the oil is too small or gasoline and water are mixed in the oil, the lubricating oil should be replaced directly;
5. The engine accessories cannot be started or it is difficult to start - the fuel volume in the fuel tank is insufficient or the fuel tank switch is not turned on;
6. The power of the forklift engine parts is insufficient - the oil supply pipeline is blocked, damaged or the shoes are leaking at the joint;
7. The engine is running unstable - the carburetor is not working well, the mixture is too little or the mixture is too lean;
8. Failure of the gasoline pump and oil transfer pump - check the rupture of the film and the falling off of the connecting rod;
9. The fuel filter is blocked - clean the forklift filter;
10. The engine body is overheated or the operation is unstable, the power is insufficient or unstable, and it can be judged that the fuel injection pump is faulty - check and eliminate;
11. Engine accessories cannot be started, difficult to start, or the fuel injection pump drive device is damaged due to insufficient power;
12. The fuel injection pump or ignition timing is incorrect - adjust the fuel injection advance angle, adjust the forklift engine to be easy to start, do not emit black smoke during work, and do not emit metal knocking sound (the fuel injection is too early); the ignition time is adjusted to: the ignition time is too late There is a metal knocking sound (sudden explosion) when accelerating too early, and black smoke or a blasting sound from the exhaust pipe when the ignition time is too late.
13. Black smoke or bubbling sound from the exhaust pipe of the engine - insufficient compression;
14. The engine power of the forklift truck is insufficient - the fuel tank vent is blocked;
15. The engine power of the forklift truck is insufficient - the fuel grade is incorrect, and the fuel can be used first according to the engine grade;
16. The forklift engine has insufficient power or unstable operation - the throttle valve is stuck or the movement is blocked - check and eliminate;
17. The power of the forklift engine parts is insufficient or the body is overheated - the cylinder is overheated;
18. The power of the forklift engine parts is insufficient - the engine is overheated and the operation time is too long;
19. Insufficient compression force of the cylinder of the forklift - the engine has not reached the precise adjustment;
20. Insufficient compression force of forklift cylinder - valve blockage;
21. Forklift crankcase pressure is too high - cylinder liner wear;
22. Insufficient compression force of the forklift cylinder - poor contact between the valve and the valve seat, and the sealing is not tight;
23. Insufficient compression force of forklift cylinder - piston ring is damaged, worn or ablated;
24. The engine power of the forklift truck is insufficient - the valve clearance is too large, and there is a valve impact sound, and the clearance should be adjusted as required;
25. The power of the forklift engine parts is insufficient - the valve clearance is too small, the valve clearance should be adjusted according to the requirements of the engine;
26. Insufficient compression force of forklift cylinder - valve stem or valve guide wear;
27. The oil pressure is too low - the grade of the oil is incorrect, and the correct oil should be changed;
28. Insufficient power of forklift engine parts - valve wear or failure;
29. The oil pressure is too low - the amount of oil in the oil is insufficient;
30. The oil pressure is too high - there is an error in the oil meter;
31. The oil pressure is too low - the oil pump is too worn or the bolts are loose and leaking;
32. The oil pressure is too low - the safety valve of the lubrication system of the forklift is stuck in the open position;
33. The oil pressure is too high - the safety valve of the lubrication system of the forklift is stuck in the closed position;
34. The oil pressure is too low - the spring of the safety valve of the lubrication system of the forklift is broken;
35. Insufficient compression force of the forklift cylinder - damage to the valve spring;
36. The engine body is overheated - the engine cooling system has leakage or insufficient cooling water;
37. The engine body is overheated - the engine fan drive belt is too loose to drive the water pump;
38. The engine body is overheated - the thermostat does not work;
39. The engine body is overheated - the forklift water pump loses its pumping function due to failure;
40. The engine body is overheated - there is too much scale in the water jacket, and the flow of cooling water is blocked;
41. The engine body is overheated - the radiator is blocked by dirt;
42. The oil pressure is too low - the oil pan lubricating oil coarse filter is blocked;
43. The oil pressure is too high - the main oil passage of the oil is blocked;
44. The pressure of the crankcase of the forklift is too high - the ventilation pipe is blocked;
45. The oil pressure is too low - the front bearing clearance of the crankshaft is too large;
46. The engine body is overheated - the valve timing is wrong.
3. Forklift steering system:
A. Steering is heavy.
1. Failure phenomenon: When the forklift turns left or right, turning the steering wheel feels heavy and laborious.
2. Fault judgment and elimination.
1) Remove the rocker arm of the steering gear of the forklift truck, and the steering wheel feels heavy. Adjust the tightness of the rack, the toothed sector, and the screw bearing. If you feel uneven tightness or internal jamming, you should check the screw, steel, etc. Balls, conduit clamps, racks and bearings for burrs or damage, repair or replace if necessary.
2) When turning the steering wheel to check, if you feel relaxed, it means that the inside of the steering gear is good. You should check whether the transmission mechanism is too tight and the lubrication is poor. If necessary, it should be adjusted and lubricated.
3) If the above conditions are all good, you should check whether the steering axle is deformed and whether the tire pressure is sufficient.
B. Steering is unstable.
1. Failure phenomenon: The steering wheel shakes and the steering wheel sways when the forklift is running. In severe cases, the direction control is difficult.
2. Fault judgment and elimination.
1) Turn the steering wheel of the forklift to observe whether the ball joints of the horizontal and straight tie rods are loose, and whether the fixing nut of the steering wheel is loose, and adjust or repair if necessary; 2) Remove the rocker arm of the steering gear and check the engagement of the rack and the tooth sector. Whether the clearance and the upper and lower bearing clearances of the screw are too large, adjust if necessary.
C, driving deviation.
1. Failure phenomenon: During driving, the forklift truck is automatically biased to one side, and the steering wheel must be firmly held to keep driving in the right direction.
2. Fault reasons and troubleshooting methods:
1) Whether the left and right tire pressures of the steering wheel are consistent;
2) After driving for a distance, stop and touch the brake drum with your hand to see if it is hot. If it is hot, it means that the brake drum is biting. If it is hot, it means that the wheel hub bearing is too tight.
Fourth, forklift lift system:
1. The gantry of the forklift cannot be synchronized when it is tilted. It can be judged that the cause of the failure may be caused by inconsistent strokes of the two tilting cylinders or different sizes of the shut-off holes at the oil cylinder pipe joints. The solution to this fault is to adjust the two. stroke of each tilt cylinder and directly replace the joint with the same orifice.
2. The gantry cannot be lifted when the forklift is empty. This fault occurs because the overflow hole of the multi-way valve is blocked. We can solve this fault by removing the impurities in the overflow hole of the multi-way valve.
3. The descending speed of the fork mast of the forklift is too fast. This fault occurs because the oil inlet speed limit valve does not work, so the maintenance personnel only need to repair the lower speed limit valve to solve it.
4. The fork gantry of the forklift will automatically drop. This fault is caused by insufficient hydraulic oil in the cylinder. To solve this fault, it is cheap to check and repair the multi-way valve and add some hydraulic oil.
Five, forklift brake system:
1. The two wheels of the forklift cannot achieve the simultaneous braking effect, that is, there is a phenomenon of partial braking. The reasons for this failure may be as follows:
1) The gap between the two brakes of the forklift is not equal or the pipeline of the brake of the forklift is blocked. The solution to this fault is to directly adjust the gap between the two brakes or dredge the pipeline;
2) The forklift brake drum already has oil stains or the brake shoes have been twisted and deformed. The solution to this fault is to remove the oil stains or directly repair or replace the forklift brake shoes;
3) There is air in the brake pipeline of the forklift. The solution to this problem is to remove the air in the brake pipeline.
2. The hand brake of the forklift is invalid. The reason for this failure is that the hand brake wire is slack. The solution to this problem is to adjust the tightness of the hand brake wire.
3. The brake of the forklift fails to work. The reasons for this failure may be as follows:
1) The gap between the brake drum and the brake shoe of the forklift is too large. The best way to solve this problem is to adjust the gap between the lower brake drum and the brake shoe;
2) The inlet and outlet valves of the forklift brake master cylinder fail. The solution to this failure is to repair its inlet and outlet valves;
3) The forklift brake friction plate has been worn excessively, and the forklift friction plate can be replaced directly;
4) The contact surface of the friction plate of the forklift truck is not enough. The solution to this fault is to repair the friction plate.
6. Forklift driving system:
1. If the clutch of the forklift has a fault that slips or does not separate, we can analyze the cause of the fault according to the following methods:
A. First check whether there is oil on the friction plate of the forklift truck or whether the friction plate is damaged. If the friction plate is oily, clean the friction plate directly. If the friction plate is damaged, replace the friction plate;
B. Then check whether the combined state of the lower release bearing is pressed on the release lever, and the length of the push rod of the sub-pump assembly can be shortened directly.
C. Check whether the free stroke of the separation bearing of the forklift is too large. If so, adjust the push rod in the sub-pump assembly to be longer; D. Check whether there is air in the oil circuit in the gearbox of the forklift. To solve this fault is to directly Remove the air in the gearbox oil circuit;
2. If the sound in the gearbox is abnormal, you can check the following two points to eliminate the fault:
A. Check whether the forklift gear wear has exceeded its service life or the bearing has been damaged. If so, replace the gear or directly replace the bearing;

B. Check whether there are other sundries in the gearbox, if there is, remove the sundries directly.


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