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Cummins Diesel Generator Fault Analysis and Troubleshooting

May 26, 2023 | Operation and Maintenance | 0 comments

Common failure causes and treatment measures


  • It is difficult or impossible to start the diesel engine

1. The weather is cold.
2. Fuel system failure:
(1) There is air in the fuel system.
(2) There is water in the fuel.
(3) Poor spraying of the fuel injector.
(4) The amount of fuel injected is small or no oil is produced.
3. The valve clearance is incorrect.
4. The compression force in the cylinder is not enough (it doesn’t feel too hard when the handcart is not operated with the decompression plate).
(1) Valve leakage.
(2) The piston ring is worn and the opening gap is too large.
(3) The piston ring is seriously bonded or broken.
(4) The cylinder head nut is not tightened or the cylinder gasket is damaged, resulting in air leakage.
5. The oil advance angle is incorrect.
6. The starting hole of the burning chamber insert is blocked.

Method of exclusion:
1. Add a small amount of engine oil into the intake pipe (but not pollute the filter element) or release the engine oil and heat it to 80~100°C before adding it into the machine.
2. Loosen the bleed screw on the fuel tank switch to remove the air. If there is air in the high-pressure fuel pipe, loosen the high-pressure fuel pipe nut at the fuel injection nozzle, open the valve, and shake the machine for a few turns.
3. Clean the fuel tank, oil pipe, and replace the diesel oil.
4. Replace plunger pay. Grind the oil outlet valve and check whether the oil circuit is blocked.
5. Grind valves.
6. Replace the piston rings.
7. Eliminate carbon deposits, or replace piston rings.
8. Tighten the cylinder head nuts evenly in diagonal order, and the tightening torque is 45~50 Nm. Damaged cylinder gaskets should be replaced.
9. Remove the fuel injector and unclog the priming hole.

  • Insufficient diesel horsepower

1. Fuel system failure:
(1) The diesel filter element is clogged and the oil supply is insufficient.
(2) The fuel injection pressure is incorrect; the spray quality is poor; carbon deposits in the nozzle hole; the needle valve and needle valve body are worn.
(3) The plunger of the fuel injection pump is worn or the oil outlet valve is leaking.
2. The compression force in the cylinder is not enough.
3. The fuel supply advance angle is wrong.
4. The valve clearance is wrong.
5. The air filter element is blocked, and the oil intake is not enough.
6. The oil pressure is wrong. (only for R170F)

Method of exclusion:
1. Clean the diesel filter elements.
2. Clean the fuel injector, adjust the fuel injection pressure, and replace with a new fuel injector.
3. Replace the plunger and grind the oil outlet valve.
4. Clean the filter element assembly, or replace with a new filter element.
5. Check the oil circuit and troubleshoot.

  • Diesel Engine Self-parking

1. Fuel system failure:
(1) Diesel is exhausted.
(2) There is air in the fuel system.
(3) The fuel injector is seized. (No fuel injection sound or very weak sound when shaking the car)
2. Lubrication system failure:
(1) No oil.
(2) Due to the blockage of the oil passage, the bearing bush is bitten, and the car cannot be shaken when shaking. (only for R170F)
(3) The oil pump does not supply oil. (Only for R17OF) 3. The connecting rod bearing bush is bitten due to the blockage of the oil hole of the oil throwing ring (only for 17OF)
4. The load suddenly increases.

Method of exclusion:
1. Add diesel.
2. Clean, grind or replace the fuel injector.
3. Add engine oil, disassemble and inspect the main bearings and connecting rod bearing bushes, and replace them if necessary.
4. Disassemble, clean and dredge the oil passage, and repair or replace the bearing bush as appropriate.
5. Disassemble the oil pump cover and check. If the barrier between the gears of the oil pump is too large, replace it.
6. Disassemble, check and clean the oil throwing ring, dredge the oil circuit, and replace the connecting rod bearing bush if necessary.
7. Take it apart for inspection. Lighten the load.

  • Exhaust smoke (when the diesel engine is working normally, the oil discharge is light gray smoke, here refers to abnormal smoke)

1. The exhaust smoke is black, indicating poor combustion.
2. Overload.
3. Poor atomization or dripping of fuel injection.
4. The air filter is blocked and the oil intake is not enough.
5. Blue smoke from the exhaust means that the oil in the cylinder is burning.
6. The gap between the valve and the valve guide is too large.
7. The piston ring is worn out, the elasticity is insufficient, or the ring groove is glued.
8. The gap between the piston and the cylinder liner is too large.
9. There is too much engine oil in the crankcase (only for 17OF)
10. White smoke from the exhaust means that there is moisture in the diesel oil, and the diesel oil should be replaced.

Method of exclusion:
1. Lighten the load.
2. Clean and grind the fuel injector or replace it with a new one.
3. Clean the element assembly in the air cleaner. Or replace with a new filter.
4. Clean the piston ring, or replace it with a new one. Repair or replace.
5. Check the oil level and drain excess oil.

  • Speeding (that is, a sudden and sharp increase in speed)

1. The speed regulation system is faulty and the fuel supply is out of control.
(1) The speed control fork is stuck.
(2) The ball head of the oil pump comes out of the speed regulating fork groove.
(3) The movement of the speed control system is blocked.
2. Caused by engine oil burning.
(1) The oil level in the crankcase is too high.
(2) The piston ring is severely worn.
(3) The diesel engine is installed incorrectly, and the nose tilt is too large.
3. The conical surface of the fuel injector is stuck and a large amount of fuel is injected.
4. The oil return hole of the oil pump core sleeve is blocked.

Method of exclusion:
Immediately stop according to the “emergency stop method during speeding”, and exclude them according to specific conditions.

Fault cases


  • Fault phenomenon

A data center purchased a 8000KW imported Cummins generator set. The engine of the unit is a 12V layout, with 6 cylinders on each side, and two high-pressure oil pumps supply oil respectively. It is only used as a backup power supply for the data center, and the actual work is less than 800 hours.

After the fifth year of use, the maintenance department made preparations for using the standby generator set 2 days in advance due to the failure of the mains power supply. (Viewed from the direction facing the control panel) The area between the exhaust branch pipe and the turbocharger becomes hot and red shortly after heavy load, and the body vibrates obviously. When the load is started, the exhaust pipe emits black smoke, and the operator stops immediately. The power supply of the data center is extremely urgent. In addition, the mains power will be out for two days, and the UPS cannot meet the power supply for such a long time. If the fault cannot be eliminated in time, the entire data center will face paralysis. If Cummins technicians are asked to overhaul, it will take at least two days to arrive. The person in charge of data center maintenance immediately organized relevant technical personnel to conduct a consultation, and analyzed the possible cause of the failure according to the failure phenomenon.

  • Failure analysis

If the muffler is clogged or the turbocharger is faulty, the exhaust will not be smooth, which may lead to high temperature in the exhaust branch pipe. Then remove the part above the outlet of the turbocharger, check the exhaust pipes and mufflers on both sides, gently move the blades of the turbine, the right turbine runs freely, and the left turbine has some resistance compared to the right , but can still rotate freely. Immediately start the motor unit, and after more than ten minutes of idling, the bronchi and the turbocharger are relatively hot, but not red. Since it has an impact on the turbocharger, in order to eliminate the fault, the mixing station was turned on to add load to the generator set. In less than 10 minutes, the exhaust branch pipe and the turbocharger appeared high temperature and red; after unloading the generator set, the engine The red exhaust branch pipe gradually darkens, which means that the turbine and muffler are working normally, and the red exhaust branch pipe and turbocharger are related to the load of the generator set.

Reinstall the muffler and exhaust pipe, and start the generator set, carefully observe the exhaust volume of the exhaust pipe, and feel whether the exhaust star and temperature are the same at the two exhaust ports by hand. The results found that: the exhaust temperature and exhaust pressure of the right exhaust pipe are lower, and the exhaust star is also small; the exhaust pressure, exhaust temperature and exhaust star of the left exhaust pipe are higher. According to the exhaust pressure, exhaust volume and exhaust temperature of the two exhaust pipes, it can be speculated that either the electronic governor is faulty, or the high-pressure pump fault causes insufficient oil supply, or individual cylinders do not work or multiple cylinders Not working.

  • Troubleshooting

First start the motor unit and check the electronic governor: open the end hole of the governor on the right side, take out the top block, and use needle-nose pliers to hold the rack and pull it out while the diesel engine is working. The engine should stop or the sound will change. But there is no response, which means that the governor is working well.

Secondly, check whether there is high-pressure oil overflowing from the oil outlet pipe of the high-pressure oil pump. The result of the inspection surprised everyone present: none of the six cylinders supplied oil. First stop the machine and remove the power cord of the oil supply solenoid valve, and then connect a power cord from the battery. Judging from the sound of the solenoid valve core, the solenoid valve is working normally. Remove the oil inlet of the oil pump. Since the oil supply tank is high, there is a certain amount of pressure oil in the oil pipe. From this, it can be seen that either the plunger of the high-pressure oil pump is stuck, or the oil delivery pump is damaged. If the plunger of the high-pressure oil pump is stuck, the rack that controls the amount of fuel supplied by the plunger cannot be pulled. It has been checked that the rack can be pulled, which means that the reason why the 6 cylinders do not supply oil is the failure of the fuel pump. Then he removed and opened the fuel delivery pump, and found that the plunger spring was broken into several sections.

In order to continue to maintain the power supply, the maintenance personnel used the spring on the engine fuel pump to temporarily replace it, added gaskets to adjust the spring pressure, restarted the generator set, and re-checked according to the above steps, and all abnormal phenomena disappeared.

According to the analysis, the real reason for the high-temperature redness of the exhaust branch pipe and the turbine of the generator set is that the 6 cylinders on the right are not working due to the failure of the fuel pump, and only the 6 cylinders on the left are working, and the electricity generated is only 40ONW, no load Or small load can basically maintain its normal work, but under heavy load (the installed power of the mixing plant is 560OkW), it is necessary to pull the asphalt mixing plant (not necessarily 56OkW, because some working devices are not always working) ) is very strenuous, it will output greater power with the increase of external load, the overload work will lead to the increase of diesel engine fuel, stars and high temperature, which will cause the exhaust branch pipe and turbocharger Heat so hot that it turns red.

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