Diesel generator maintenance & troubleshooting
Case 1: Diesel engine cannot start
There are various reasons why diesel engines can’t start, mainly the following four points: Start the system, Fuel system, The compression stroke pressure is insufficient, Influence of ambient temperature
- Starting system & Failure analysis
<1> Starting battery voltage is low, and the actual capacity is insufficient (the display voltage is a virtual voltage)
<2> The wiring of the starting battery cable and motor is wrong
<3> Starting motor electromagnetic switch failure
<4> Starting contactor, Callebit, Wilson, and other engines failures
<1> Use a multimeter to measure whether the voltage of the single battery and the DC output of the charger is normal, check the liquid level of the lead-acid battery, and add distilled water in due course;
<2> Disassemble the motor, check and adjust the contacts in the electromagnetic switch, if the contacts are burned out, replace the electromagnetic switch;
<3> Check if the battery negative cable is grounded (chassis), the wiring is wrong, just reconnect the cable;
<4> Use a multimeter to measure the resistance of the starting contactor coil of Cummins, Callerbit, and Wilson diesel engines (the resistance is generally in the tens of ohms), if not normal, replace the contactor;
- Fuel system &Failure analysis
Air leaks in the fuel system
Low-pressure fuel pipe air discharge method: loosen the bleed screw plug on the fuel injection pump, press the hand pump of the fuel delivery pump until the diesel overflows without bubbles, then tighten the screw plug and tighten the hand pump. High-pressure oil pipe air discharge method: loosen the high-pressure oil pipe joints of the fuel injection pump one by one, start the diesel engine until the oil is discharged from each cylinder, and then tighten the high-pressure oil pipe joints. The difference between the exhaust air method of Cummins diesel engine oil circuit and other diesel engines is that it relies on starting the diesel engine to complete.
- Insufficient compression stroke pressure & Failure analysis
<1> Valve leakage;
<2> Excessive wear of the piston ring.
<1> Remove the cylinder cover and cylinder head, check the valve clearance, valve spring, valve guide, and valve seat sealing. If the valve sealing line is not continuous, the valve can be ground into a continuous smooth line with sanding;
<2> Take out the piston and replace the piston ring.
- Influence of low ambient temperature & Failure analysis
<1>The heater is faulty;
<2>The diesel oil is too thick.
<1> Remove the side cover of the heater, check whether the AC input terminal connection and voltage are normal, if normal, the heater is broken, replace the heater;
<2> Add kerosene to diesel proportionally or choose No. 10, No. 20, and No. 35 (the numbers indicate the freezing point temperature, and the freezing point of No. 10 light diesel is -10 degrees).
Case 2: Abnormal color of exhaust smoke from diesel engine
When the diesel engine is running normally with load, the exhaust smoke is generally light gray, and when the load is slightly heavier, it may be dark gray. Abnormal exhaust smoke color here refers to: The exhaust emits black smoke; White smoke from the exhaust; Blue smoke from the exhaust.
- Exhaust emits black smoke (indicating the imperfect combustion of diesel in the combustion chamber)
<1> Diesel engine is running with overload;
<2> The injector drips oil, and the atomization is not good;
<3> The fuel supply time is too early.
<1> Adjust the load to make it within the rated range;
<2> When the diesel engine is running at idle speed, loosen the injector high-pressure oil pipe joints one by one to stop the fuel injection of the fuel injector and observe the color of the exhaust: When the fuel injector is not malfunctioning, the speed of the diesel engine will change after the fuel injection is stopped. Decreased significantly. When the fuel injector is faulty, the speed of the diesel engine changes very little after the fuel injection is stopped, and the exhaust gas does not emit black smoke. Check and adjust the fuel injector;
<3> According to the requirements of the manual, check and adjust the fuel supply advance angle.
The injector has the following requirements: it must have a certain injection pressure, a certain range, a certain spray cone angle, and a good spray. At the end of the fuel injection, the fuel can be stopped quickly, and there is no oil leakage or oil leakage.
- Exhaust gas emits white smoke (indicating that the diesel is not burned in the combustion chamber) failure analysis
<1> The cylinder head gasket is damaged;
<2> The fuel supply time is too late;
<3> There is water in the diesel oil.
<1> Replace the cylinder head gasket;
<2> According to the requirements of the instructions, check and adjust the fuel supply advance angle;
<3> Install fuel oil and water separator.
To get a good seal of the cylinder, a cylinder head gasket must be added between the cylinder head and the cylinder block. The cylinder head is fastened to the cylinder block with bolts. There should be a certain order when tightening the bolts, that is, in the order of symmetrical expansion from the center to the surroundings. The last time the torque wrench is tightened according to the torque value specified in the manual. Remove the bolts and vice versa.
- Exhaust emits blue smoke (indicating that the organic oil is strung into the combustion chamber to burn)
<1> The oil level of the oil pan is too high;
<2> The oil ring is stuck in the ring groove or broken;
<3> The gap between the connecting rod bearing bush and the connecting rod journal is too large.
<1> Keep the oil sump at the full scale of the scale, and drain some oil in due course;
<2> Clean the carbon deposit in the piston ring groove and replace the oil ring;
<3> Remove the oil pan, connecting rod bolts, and take out the bearing bushes, check whether there are signs of burnout on the bearing bush surface. If so, replace the connecting rod bushings.
Case 3: diesel engine oil pressure is low
<1> The oil level in the oil pan is low;
<2> The spring of the oil pressure regulator is broken;
<3> Aging oil leakage of the rubber ring gasket of the oil filter (usually domestic diesel engines);
<4> The oil pressure gauge is broken;
<5> The oil filter in the oil pan is blocked.
<1> Keep the oil pan at the full scale of the scale, and add oil in due course;
<2> Replace the spring of the oil pressure regulator;
<3> Replace the rubber ring pad;
<4> Replace the pressure gauge;
<5> Remove the oil pan and clean the oil filter.
Oil pressure adjustment method: Unscrew the oil seal nut on the regulating valve, loosen the lock nut and turn the regulating bolt with a flat screwdriver, screw in the regulating bolt, and the pressure will increase. On the contrary, if the pressure is reduced, adjust to the specified position, and then tighten the nut and the oil seal nut.
Case 4: When the diesel engine is running, the oil temperature rises above 90 degrees, and the exhaust emits blue smoke
The connecting rod bolts are loose and a sign of bush burning.
Check whether the connecting rod bolts are loose, disassemble the connecting rod bearing bush, and see if there are signs of burnout on the surface of the intuitive connecting rod bearing bush. If it turns out, replace the bearing bush and tighten the connecting rod bolt with a torque wrench according to the torque required by the manual.
If you encounter the above situation, you should stop emergency. Find out the cause of the failure and prevent major accidents (such as flying cars). When the diesel engine is running normally, the oil temperature is generally between 70 and 90 degrees.
Case, after the diesel engine technical maintenance, no-load test engine, three-phase AC synchronous generator output voltage 360V
<1> intake, exhaust valve clearance were adjusted to 0.30mm , 0.35MM normal;
<2> Replace the cylinder head gasket;
<3> Check the fuel injector and fuel injection pump;
<4> Clean up the carbon deposit on the piston and replace the piston ring;
<5> The three-phase AC synchronous generator is operating normally.
Case 5: When Wilson Diesel Engine is running automatically < AUTO >, there is a low oil pressure warning and shutdown
<1> The ” 606 ” controller panel oil pressure low indicator light is on;
<2> The oil in the oil pan is at the static full scale of the scale;
<3> Check that the oil filter is normal;
<4> Check that the oil collector in the oil pan is normal.
The above analysis: It is judged that the oil pressure sensing plug is faulty. Unplug the oil pressure sensor plug connection, manually start the diesel engine, the unit is operating normally. The oil pressure sensor plug is broken. After replacing this component, simulate a mains power failure, disconnect the mains sampling air switch < 3P >, the diesel engine will start automatically < AUTO >, and the unit is operating normally.
This failure occurs:
<1>Check whether the diesel engine oil is overflowing;
<2>Check the oil pressure sensor plug.
Case 6: Common failures of high-pressure fuel injection pumps
<1> When the diesel engine is running, the fuel injection sub-cylinder does not deliver oil or produces less oil;
<2> After the diesel engine is stopped, the hand pump of the fuel delivery pump is pressed, and the fuel injection sub-cylinder continues to overflow with diesel.
<1> The plunger or spring of the fuel injection pump is faulty;
<2> The delivery valve or spring of the fuel injection pump is faulty.
<1> Replace the plunger or spring of the fuel injection pump;
<2> Replace the fuel injection pump outlet valve assembly or spring.
There are two pairs of precision couplings in the plunger fuel injection pump body, one pair is a plunger and a plunger sleeve, and the other pair is an oil outlet valve and an oil outlet valve seat. The oil outlet valve assembly is installed on the plunger assembly and is pressed tightly, and the two parts are tightly attached to prevent oil leakage. When disassembling the fuel injection pump, pay attention to each sub-cylinder part that should be marked and put together. The plunger assembly and delivery valve assembly cannot be exchanged and must be arranged in pairs. The disassembled parts are cleaned and blown-in diesel oil. The fuel injection pump assembly must be adjusted after working for 1000 hours or after the replacement parts are assembled. Due to the high degree of precision of the fuel injection pump, this work must be carried out by a more skilled technician under certain equipment conditions.
Case 7: When Cummins diesel engine is running, the phenomenon of “traveling” appears
<1> Check that the diesel filter is normal;
<2> Check the cleanliness of the air filter element;
<3> Replace the frequency circuit board, test the machine without load, the fault still exists.
The above analysis: It may be that the fuel supply of the fuel PT pump is not smooth. After the PT pump was checked, the machine was tested without load, and the fault was still not eliminated. According to maintenance experience, it is judged that it is caused by the slight abrasion of the plunger and coupling parts in the actuator. Replace the actuator ( PAPT NO3408324 ), test the machine with load for 60 minutes, and the unit is operating normally.
Before using the diesel fuel, it must be allowed to stand still and filtered.
Case 8: When Wilson Diesel Engine is running automatically < AUTO >, there is a high water temperature warning and shutdown
<1> The ” 606 ” controller panel water temperature high indicator light is on, the LCD screen displays the water temperature 100 degrees, and the AC load is 140A ;
<2> The thermostat turns on the cooling water to form a large circulation;
<3> Check that the water temperature sensor plug is normal;
<4> The cooling water in the water tank is full.
The above analysis: It is judged that the water tank condenser is too dirty, which caused a high water temperature alarm and shutdown. Remove the water tank and clean the condenser. After installation, the diesel engine will start automatically < AUTO > and the unit runs normally.
Add alkali to the water for cleaning the condenser (tank) appropriately, that is, put more water and less alkali to avoid damage to the condenser (tank).
Case 9: When the diesel engine is running automatically 〈AUTO 〉, there is a low oil pressure warning and shutdown
<1> The low oil pressure indicator on the control panel is on;
<2> The oil in the oil pan is at the static full scale of the scale;
<3> Check that the oil filter is normal.
The above analysis: It is judged that the oil pressure controller is faulty.
Remove the oil pressure controller panel, use a multimeter to measure the AC voltage of 385V, the input voltage is normal. Check that the contacts of the oil pressure controller are in poor contact. Wipe and adjust the contacts. The diesel engine starts automatically < AUTO > and the unit is operating normally.
Case 10: the diesel engine automatically < AUTO > is running, appear high water temperature shutdown alarm
<1> The high water temperature indicator on the control panel is on, and the water temperature gauge reads 68 degrees:
<2> The cooling water in the water tank is full;
<3> Check that the fan belt tension is within the specified range, the water pump is operating normally, and the diesel engine does not leak water.
The above analysis: It is judged that the thermostat is not turned on.
Remove the thermostat and replace it, the diesel engine will start automatically < AUTO >, and the unit is operating normally.
In the closed forced circulating water cooling system of a diesel engine, a thermostat is used to change the circulating flow of cooling water to achieve the purpose of automatically controlling the cooling intensity. The thermostat is installed at the water outlet of the cylinder head. Therefore, in the maintenance process, it is not allowed to remove the thermostat at will, which will affect the normal use of the diesel engine. The initial opening temperature of the thermostat is 68—72 degrees, and the full opening temperature is 80—86 degrees, forming a large circulation of cooling water. The cooling water must be distilled water and add anti-rust and antifreeze liquid.
Case 11: When the diesel engine is idling, the three-phase AC synchronous generator makes an abnormal noise
The rubber ring pad of the back wheel of the synchronous generator is worn.
Considering that the connection between the diesel engine and the synchronous generator is push-pull. Therefore, while removing the fastening bolts of the synchronous generator, use a hoist to raise it and pull out the synchronous generator. It was found that the six bolts of the back wheel were equipped with 24 rubber ring pads and there was no wear left. Replace its spare parts, and the diesel generator set is operating normally.
When the diesel generator set is running, if an abnormal sound is heard, it should be shut down immediately to find out the cause of the fault and eliminate it.
Case 12: Adjustment of diesel engine fuel injection advance angle
For good combustion, diesel engines operating normally, and the most economical fuel consumption, the fuel pump checksum must be adjusted fuel injection timing at the time of installation.
When adjusting, turn the ring gear of the flywheel so that the timing zero-degree line on the flywheel is aligned with the pointer of the inspection window on the flywheel housing. The piston of the first cylinder is at the beginning of the expansion stroke. , Exhaust valve is closed>. Remove the side cover of the fuel injection pump and turn the adapter plate to make the plunger spring of the first cylinder just compressed. Then turn the flywheel in the opposite direction (clockwise) for about 23 degrees, tighten the fuel injection pump bolts (adjust the speed of the governor diesel engine is low, loosen the bolts on the adapter plate to fine-tune the driveshaft joint engraved on the index Thread, 3 degrees per grid, and then tighten the bolts>. In the actual maintenance work, the fuel supply advance angle is generally checked. The fuel supply advance angle refers to the crankshaft angle of the piston before the top dead center of the compression stroke when the oil is just coming from the outlet of the fuel injection pump. Because checking the fuel supply advance angle is more convenient and accurate than the fuel injection advance angle. If the fuel supply advance angle of a diesel engine is found, if you want to know the fuel injection advance angle of the engine, you only need to subtract 8 degrees from the value of the fuel supply advance angle, which is the fuel injection advance angle.
Too early or late fuel supply time of diesel engines is harmful. The fuel supply time of the diesel engine is too early, that is, the fuel supply advance angle is too large. When the piston is not far from the top dead center, the fuel injection pump starts to supply fuel. At this time, due to the low pressure and temperature of the cylinder gas, the ignition delay period is prolonged. As a result, the diesel engine is not easy to start, runs rough, knocks cylinders, decreases power, emits black smoke from the exhaust pipe, and causes early wear and tear of mechanical parts. The fuel supply time is too late, that is, the fuel supply advance angle is too small. Since the combustion is carried out after the piston has descended in the working stroke, this will reduce the power of the diesel engine and increase the fuel consumption rate. It is easy to cause the body temperature to be too high and the cooling water to boil. The exhaust pipe emits white or black smoke.
The fuel injection advance angle of the diesel engine is different, and the adjustment should be carried out according to the instructions.
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