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;
12. If the forklift generator does not generate electricity, check the following items:
1) The fan drive belt is too loose, slips or breaks;
2) The charging circuit is open-circuited, grounded or short-circuited, that is, the external circuit from the forklift generator armature terminal to the ignition switch is blocked;
3) The regulating voltage of the regulator is too low, the magnetizing coil, the resistance ablation is damaged, the primary and secondary contacts are ablated, dirty, etc.;
4) The insulation of the brush is damaged, the spring force of the brush is too weak, the brush is stuck in the frame, and the contact with the slip ring is poor;
5) The diode is broken down, short-circuited or open-circuited, and the diode and the stator winding are loose or broken;
6) The insulation of the forklift generator armature and the magnetic field terminal is damaged or the contact is poor;
7), the collector ring insulation is broken down;
8), the stator and rotor windings are open circuit, short circuit or grounding;
9) The rotor claw is very loose;
10) The maximum power transistor circuit at the end of the transistor voltage regulator is open, thereby cutting off the circuit of the excitation current of the alternator, causing the generator not to generate electricity.
2. Forklift engine system:
1. Crank connecting rod mechanism
1) Repair method for cracked cylinder block and cylinder head
In addition to the high temperature parts such as the combustion engine of the forklift truck and the vicinity of the valve seat, cracks or holes in other parts can be repaired by epoxy resin adhesive bonding. If the crack is in a place with little stress and the length is less than 50mm, it can be filled with screws. If the crack is longer or the hole is larger, it can be filled with a patch. If the crack is in the part with high stress, it should be repaired by welding repair method. The repaired cylinder block and cylinder head still need to be hydraulically tested to confirm that there is no leakage before they can be used.
2) When the concave or arched surface of the cylinder block and cylinder head exceeds the forklift manual, it should be repaired according to the following methods.
There are protrusions around the plane screw holes of the cylinder block, which can be ground with oil stone, plane grinding wheel, or smoothed with a fine file. The cast iron cylinder block and cylinder head are uneven, which can be repaired by milling and grinding. The warpage of the cylinder head can be corrected by the knocking method. When the thickness of the cylinder head is less than 2mm than the original standard thickness (that is, measured from the lowest point of the combustion chamber), a new cylinder should be replaced or an additional cylinder should be installed for continued use.
3) Maintenance methods for other parts of the cylinder block and cylinder head.
For the repair of the corrosion of the water channel, the water channel of the aluminum alloy cylinder head is easy to corrode. The light one can be repaired by epoxy resin glue, and the heavy one can be re-opened after surfacing welding, or the repair plate can be used. Repair of the spark plug seat hole, if the spark plug seat hole is damaged, it can be repaired by the insert method. The cast iron cylinder head is generally made of medium carbon steel as the inner sleeve, and the aluminum alloy cylinder head is generally made of copper. Repair of screw hole damage, screw hole damage is generally caused by impact wear and metal corrosion, the most common is the sliding button, improper installation of the stud or excessive torque will also cause the screw hole to expand. When the thread of the screw hole is damaged more than two teeth or less, it can be repaired by the insert method. The damaged screw hole is enlarged to a certain size and a new thread is tapped. With the same thread as the original specification, the damaged screw hole can also be enlarged and then matched with stepped bolts.
2. Maintenance of gas distribution system
1) The working surface of the valve and valve seat should be polished before grooves, widening, or spots and depressions after ablation.
2) When the wear of the valve stem exceeds 0.05mm, or when there is obvious bending through detection, the valve should be replaced.
3) The valve stem and valve guide are loose, and the valve and valve guide should be replaced.
4) When the valve spring is broken, the free length is shortened, the elasticity is reduced and the deformation is not in compliance with the regulations, the valve spring should be replaced.
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. Fault 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 braking system:
fault phenomenon
1. Brake failure
1) Step on the brake pedal to feel the brake failure. First check whether the oil cup of the master cylinder is short of oil. If there is oil, it means that the leather wrist in the master cylinder is not tightly sealed, causing internal leakage. If there is no oil, it means that the brake system pipeline is leaking or the apron behind the brake master cylinder is leaking oil. You should add brake oil, drain the air in the system pipeline, and then step on the pedal to find the leak.
2) The brake pedal is very high and hard, which can directly eliminate the lack of oil or oil leakage in the system pipeline. Remove the oil outlet pipe of the brake master cylinder, and step on the brake pedal to see if oil comes out. If the oil comes out, it means the brake master cylinder pipe. If the road is not blocked, the oil outlet pipe of the master pump can be tightened. Loosen the brake pipe on the wheel, press the pedal to see if oil comes out, if the oil comes out, it means that the pipeline is smooth, then it can be determined that there is oil on the brake drum and the brake shoe or the pressure spring of the fixed shoe falls off. If there is no oil or the brake pedal cannot be stepped on, it means that the oil outlet joint of the master cylinder is blocked.
2. Bad braking
Fault phenomenon:
1) The forklift truck cannot decelerate and stop in time after pedaling the brake pedal several times.
2) Although the pedal height is normal, it feels weak to step on and cannot stop in time.
3) The pedal is high and hard and even rebounds, and the braking effect is not good.
Fault reasons and troubleshooting methods:
1) If you step on the brake pedal several times in a row, the pedal gradually rises, and after the rise, you continue to step down without lifting your foot, you can feel the pedal has elasticity, you can release the pedal and stop for a while before stepping on it. In order to have air in the brake system, it should be exhausted. Air exhaust should start from the brake master cylinder and then to each brake cylinder. Exhaust method: One person is responsible for stepping on the brake pedal, and the other person is responsible for exhausting. First step on the brake pedal to the bottom and do not release it, then loosen the exhaust screw, and after the brake fluid mixed with air is sprayed out, tighten the exhaust screw, relax the brake pedal, and wait for the brake pedal to return to its full position. After that, depress the brake pedal to the bottom again and continue to release the air, so that the air can be completely exhausted several times.
2) If the brake fails to work when you step on one brake pedal, step on the brake pedal several times, the pedal position gradually rises, and the braking effect is good, indicating that the free travel of the pedal is too large or the brake shoes are not connected to the brake. The drum gap is too large. At this time, check and adjust the gap between the master cylinder and the push rod of 1.5 ~ 2.5 mm to make it within the specified range, and then check and adjust the gap between the brake shoe and the brake drum to 0.3 ~ 0.5 mm.
3) If the brake pedal is continuously pressed, the position of the pedal can gradually increase, and if you continue to step down without lifting your foot, you do not feel the pedal is elastic, but there is a feeling of sinking, which means that there is a leakage in the braking system. First check whether there is oil in the oil cup of the brake master cylinder. If the oil in the oil cup is normal, it means that the leather wrist of the master cylinder is broken. If there is no oil, it means that there is a leakage in the brake system. Where there is leakage, if there is leakage, it should be treated by fastening, riveting or replacement.
3. Brake deviation
Fault phenomenon:
When the forklift is working, the forklift deviates left or right after the brake pedal is depressed. The fundamental reason for the deviation of the brake is that the braking forces of the two wheels are different.
Cause of failure and troubleshooting method: Carry out road braking test on the faulty forklift. If the forklift swerves to the left when braking, it means that the right wheel brakes slowly or the braking force is insufficient; otherwise, it means that the left wheel brakes slowly or the braking force is insufficient. If it can be determined that the braking force of a wheel is insufficient or slow, you can first check the brake oil pipe of the wheel to see if it is flattened and leaking oil. If so, it should be replaced or riveted. If the wheel pipeline is normal, the brake cylinder can be exhausted first and then difficult. If there is no air, the gap between the brake drum and the brake shoe should be adjusted by 0.3 to 0.5 mm. If the fault is still not resolved, the fault is inside the wheel brakes. The wheel brakes should be removed, and the brake shoes should be checked for oil stains, ablation, cracks, and loose riveting of the brake shoes. Observe whether the brake shoe is seriously worn (the distance from the brake shoe surface to the upper plane of the rivet head should not be less than 0.5 mm). Check that the brake drum is worn and grooved or has obvious groove marks and out-of-roundness. It should be repaired by wok cutting, and the maximum amount of lock cutting should not exceed 4 mm, otherwise, replace the new brake drum. Note: There should be a large contact area between the brake shoe and the brake drum to ensure the same braking force. Check whether the piston of the brake cylinder is stuck and whether the leather wrist
Swelling and aging. Insufficient tire pressure and different wheel tightness are also one of the reasons why the brake deviation is easily overlooked.
4. Braking drag
Fault phenomenon: After the forklift lifts the brake pedal, the brakes on both sides or one side of the wheels cannot be completely released, which affects the forklift's difficulty in starting or insufficient driving power.
Fault reasons and troubleshooting methods:
After the forklift has been working for a period of time, touch the brake drums of the wheels on both sides by hand. If all wheel brake drums are hot, it means that the fault occurs in the brake master cylinder; if individual wheels are hot, it means that the fault is in the wheel brake. If the fault is in the master cylinder, check the free stroke of the pedal first. If the free stroke does not meet the requirements, adjust the free stroke of the pedal by 10-15 mm; if the free stroke meets the requirements, open the oil cup cover of the master cylinder, Observe the oil return of the master pump. If the oil cannot be returned or the oil return is slow, the master pump should be disassembled for inspection and replaced if necessary. If the fault is in the wheel brake, loosen the exhaust screw first. If the brake fluid is sprayed out rapidly and the brake shoes return, the pipeline is blocked, and the pipeline should be cleared; if the brake shoes cannot be returned, The gap between the brake shoes and drums should be adjusted. If there is no effect after the above inspection and adjustment, the brake drum should be removed, the condition of the piston seal of the wheel cylinder and the return spring of the brake shoe should be checked, and repair and replacement should be carried out if necessary.
5. Excessive consumption of brake fluid
Fault phenomenon: After the brake fluid is filled up, the forklift runs for a short time and consumes it.
Fault reason and troubleshooting method: First, check whether there is oil dripping from the bottom of the wheels on both sides. If there is no oil leakage in the brake cylinder. Then check whether the copper pipes or joints are leaking oil, if there is oil leakage, replace it; if not, it means that the oil leakage is in the brake master cylinder. First observe whether there is oil leakage at the dust jacket of the master cylinder, if so, replace the apron; if not, open the oil cup cover and step on the brake pedal to see if the oil is flowing upwards. If the push rod clearance is too large, it can be adjusted. Release the brake pedal and channel the oil upwards, which is caused by the excessive clearance between the brake drum and the brake shoe, and can be adjusted.
Five, 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.
6. 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) Air has entered 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 forklift brake master cylinder inlet and outlet valve If it fails, 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 forklift friction plate is not enough. The solution to this fault is to repair the friction plate.
Seven, 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 the friction plate of the forklift has oil stains on it or whether the friction plate is damaged. If the friction plate is stuck with oil, 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. You can directly shorten the length of the push rod of the sub-pump assembly. C. Check whether the free stroke of the release bearing of the forklift is too large.