Common Faults and Troubleshooting of Cummins Engine

This article will guide you to know about the common faults and troubleshooting of Cummins engine.

1. Diagnosis and treatment of engine starting difficulty or failure to start and exhaust pipe emitting a large amount of ash and white smoke.

The engine is difficult to start, and the exhaust pipe discharges a large amount of gray smoke, which is diesel vapor.

Reason

a. The engine temperature is too low, diesel oil is not easy to evaporate and burn.

b. Poor atomization of injector

c. The oil supply is too late.

d. The oil supply is too small and the mixture is too lean.

e. Cylinder leakage is too much, compression can not reach the ignition temperature.

Diagnosis and treatment

a. If the engine temperature is too low in cold season, check whether the low temperature starting preheating device fails, that is, whether the preheater control circuit has open circuit, short circuit or preheater failure.

b. If the low temperature preheating device is normal, check whether the injection timing is correct. Turn the engine and insert the engine camshaft timing pin, that is, when it is located at the upper dead center of cylinder compression, check whether the fuel pump camshaft lock pin can be inserted. If it cannot be inserted, it indicates that the injection timing is wrong and needs to be adjusted.

c.The spray quality of each cylinder injector should be checked to meet the requirements.

d. If the first two items are normal, check if the oil supply is too small. During cold start, due to the low temperature in the cylinder, the fuel viscosity is large, and the evaporation condition is poor, the starting oil supply is required to be larger than the rated oil supply.

e. Finally check the cylinder pressure and repair it when the pressure difference is very far.

2. Diagnosis and treatment of engine starting difficulty or failure to start and exhaust pipe emitting a lot of black smoke.

The engine is difficult to start, and the exhaust pipe emits a large amount of black smoke, which is the result of incomplete combustion of the diesel oil.

Reason

a. Diesel oil is of poor quality.

b. The air intake is not smooth and the air filter is blocked.

c. The injection timing adjustment is too early.

d. Injector needle valve sealing is poor, there is dripping oil leakage phenomenon.

e. The injection pressure is too low

f. The fuel supply of the fuel injection pump is too large and the combustion is deteriorated.

g. Low cylinder pressure and poor atomization.

Diagnosis and treatment

a. Determine if the diesel quality meets the requirements.

b. Check if the air filter is clogged.

c. Check if the injection timing is too early. Turn the engine and insert the engine camshaft timing pin, that is, when it is located at the upper dead center of cylinder compression, check whether the fuel pump camshaft lock pin can be inserted. If it cannot be inserted, the fuel injection timing is wrong and needs to be adjusted.

d. Check whether the fuel pump supply is too large.

e. Check if the fuel injection pressure and spray condition of the fuel injector are good, and the fuel injector should not have a dripping phenomenon.

f. The working condition of each cylinder shall be checked by the oil-breaking method.

g. If the above inspection is normal, but the fault remains, check whether the cylinder pressure and piston, piston ring and cylinder clearance are abnormal, whether the cylinder gasket is damaged or the valve is not tightly closed, etc.

3. Diagnosis and treatment of engine thermal starting difficulties

The cold start of the engine is good, but after running for a period of, temperature rises and the engine turns off. It is difficult to start again.

Reason

It is mainly caused by serious wear of plunger pair of fuel injection pump and needle valve pair of fuel injector. When the hot car starts, the fuel viscosity is reduced due to the high temperature of the fuel injection pump and fuel filter, and the starting speed is low, and most of the diesel oil leaks from the worn gap, resulting in insufficient starting oil and unable to start.

Diagnosis and treatment

a. The method of emergency elimination is: the car is hung up and driven by other cars. Using the speed of the car to drive the high-speed rotation of the engine, so that the diesel can not leak, to ensure the starting fuel supply (this method is not recommended, because the cylinder pressure of Cummins supercharged engine is relatively large, the impact force on the connecting parts when the trailer starts is large, affecting the vehicle service life).

b. When the plunger pair or needle valve pair is seriously worn, the new product should be replaced after the inspection and debugging of the fuel injection pump test bench.

4. Diagnosis and treatment of engine with normal low speed and short time high speed with too little smoke exhaust

The engine idle speed is good, and the throttle speed can be increased rapidly. However, the continuous boom throttle speed is not easy to rise, the driving is weak, or the medium speed is not able to drive. This is caused by insufficient low pressure oil supply.

Reason

a. Fuel filter or the oil-water separator is blocked.

b. Low pressure oil circuit is not smooth.

c. Insufficient oil supply in oil pump or the oil filter is blocked.

d. The inlet valve of fuel tank cover is invalid.

All of the above conditions can cause the fuel pressure of the low pressure oil chamber of the fuel injection pump to be insufficient, and only the oil supply amount required for the small load can be maintained. when It is necessary to use more oil supply for large and medium load, it cannot be satisfied, resulting in a weak driving.

Diagnosis and treatment

a. Check whether the intake valve of the tank cover is invalid, if it fails, a certain vacuum degree will be formed in the tank, and the diesel oil cannot be sucked out. Most of this phenomenon is caused by the loss of fuel tank cover and sealing with airtight plastic cloth.

b. Check if there is any concavity in the low pressure oil pipe and whether there is any blockage at the inlet pipe joint filter.

c. If the fuel filter or oil-water separator is not replaced for a long time, it should be replaced in time.

d. Check if the oil pump is working properly. If the oil supply is insufficient, replace or repair the oil pump in time.

5. Diagnosis and repair of low engine speed but no high speed, too little smoke exhaust

The low speed of the engine is good, but the speed can not be increased at the time of acceleration, and the driving is weak, which is caused by insufficient circulating oil supply.

Reason

a. The fuel injection pump is not adjusted properly, so that the fuel supply is reduced.

b. The governor spring is reduced in elasticity due to fatigue. When the throttle is stepped to the end, the oil adjustment lever can not move forward to the head, so that the fuel supply of the fuel injection pump is reduced and the engine cannot reach the rated speed.

c. The fuel pump plunger and the sleeve, the injector needle valve and the needle valve body are seriously worn, so that the diesel oil leakage increases when the oil is pumped, and the oil supply amount is relatively reduced.

d. Improper adjustment of the throttle control lever, or the accelerator pedal pin is too far, the accelerator pedal cannot be placed in place, resulting in too little oil supply at full load.

e. There is air in the oil circuit

Diagnosis and treatment

When the engine power is insufficient, if the low speed is good and the smoke exhaust is normal, it means that the engine burns well, that is, the diesel injection quality is good, the fuel supply start time is normal, the cylinder sealing is good and the intake air is sufficient.

a. In the case of normal low-pressure oil circuit, first check whether the degree of looseness of the accelerator pedal connecting pin and the length adjustment of the connecting rod are properly adjusted. When the throttle is stepped to the end and the governor arm is at the maximum position, the high speed limit screw should be in contact with the limit block. Otherwise it should be adjusted.

b. Drain the air from the oil circuit.

c. Debug the fuel injection pump on the test bench to eliminate the fault.

Hope the above methods can help you solve common problems about Cummins generator.