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The Reason Why Cummins Diesel Generator Set Can Not Start Normally

Nov. 05, 2021

Recently, the after-sales maintenance department of Starlight Power received a repair request. When a user’s Cummins diesel generator set was operated on a weekly test run in accordance with the diesel engine maintenance regulations, the diesel generator started smoothly, but then an ultra-high-speed alarm was issued and shut down. After inspection, all parameters of the diesel engine were normal, but failed for 3 consecutive startups. The control panel issued a low battery voltage alarm. The measured battery voltage was 12.3V, which was slightly lower than the normal float voltage (normal value is 12.8V). Jiangsu Starlight Electricity Equipments Co.,Ltd. immediately sent experienced after-sales technicians to the door for troubleshooting.

 

The trouble finding process and analysis of the diesel engine cannot start normally. The after-sales personnel measured that the voltage at both ends of the diesel engine battery was 12.3V, which was slightly lower than the normal voltage. It was preliminarily predicted that the cause of the fault was that the battery voltage was too low or the capacity was insufficient. Charge the diesel engine battery for 6 hours and then measure it again. It shows that the battery voltage is 13.3V, but the diesel generator still cannot start normally, so temporarily remove the battery cause. The control panel of the diesel engine can send out the start command normally, and all the parameters are in the normal state, so remove the controller fault.

 

Next, our after-sales personnel check whether the diesel engine fuel system is normal.

First, confirm that the fuel tank of the diesel engine is full of fuel and the fuel gauge shows the same value. Secondly, check the status of the oil circuit to confirm that the oil circuit is unblocked. Finally, check the fuel injection system, open the high-pressure fuel pump outlet pipe to start the oil machine, and find the oil pump outlet. There is no oil leakage, and the fuel cannot be delivered to the combustion chamber of the engine, causing the diesel engine to fail to start. Through the above investigation and analysis, it is preliminarily determined that the diesel engine cannot start normally because the Cummins diesel generator's high-pressure fuel system does not supply fuel.

 

diesel engine


In order to troubleshoot the root cause of the failure, it is necessary to further understand the working principle of high-pressure fuel. The high-pressure fuel consists of two parts, namely the high-pressure fuel injection pump and the electronic governor system. The electronic speed control system consists of two parts: a speed control controller and an electromagnetic actuator. The high-pressure fuel system does not supply fuel, which may be caused by a failure of the high-pressure fuel injection pump, speed control controller or electromagnetic actuator. Among them, the electromagnetic actuator control signal is sent by the speed control controller. The operating voltage of the Cummins diesel generator electromagnetic actuator is measured at 9.3V at the moment of startup. The speed governor can output signals normally, temporarily eliminating the speed control controller fault.

 

According to related technical data, the model of Cummins diesel generator electromagnetic actuator is ADC100, and the operating voltage should be greater than 10V at the moment of starting. The operating voltage of electromagnetic actuator at the moment of starting the diesel engine measured on site is 9.3V, which is less than the minimum operating voltage. Therefore, the fundamental reason for judging that the high-pressure fuel injection pump does not deliver oil is that the instantaneous voltage of the throttle solenoid valve of the control circuit part is too low, and the fuel cannot enter the high-pressure fuel pump. When the output voltage of the speed controller is too low, it is necessary to determine whether the control circuit of the speed controller is faulty or the operating power supply voltage is low.

 

By consulting related technical data, we know that the working power of the speed controller comes directly from the diesel generator battery. When the battery capacity of the diesel engine is insufficient, the battery voltage is low when the diesel engine starts, and it cannot provide enough power to the speed controller to make the speed adjustment. The voltage output from the generator to the electromagnetic actuator is lower than 10V, and the solenoid valve cannot be opened normally, causing the fuel to be unable to be delivered to the engine combustion chamber, causing the diesel generator to fail to start normally. After replacing the battery with a new one, restart the diesel generator, and the diesel engine starts normally. And the voltage of the speed control controller measured at the moment of starting is 10.9V.

 

So far, the reason why the Cummins diesel generator set used by this user cannot start normally has been found out, and the direct cause is insufficient battery capacity. The battery has been used for a long time and the capacity has been severely reduced, resulting in a low voltage at the start of the diesel engine, which is unable to provide the required voltage for the solenoid valve to work, causing the solenoid valve to fail to open normally, and the fuel cannot be delivered to the engine combustion chamber, causing the diesel engine to fail. start up.

 

Summarize:

The direct cause of the Cummins diesel generator set cannot start is insufficient battery capacity, but the process of determining the cause is longer. First, use a multimeter to measure the battery voltage. Secondly, after the battery is charged, the voltage at both ends of the battery is measured with a multimeter, and the result is within the normal range, and the cause of the battery is ruled out. Finally, when the diesel generator set broke down for the first time, there was an overspeed phenomenon, and the diesel engine issued an overspeed warning, so more attention was turned to the fuel system.

 

Tips from Jiangsu Starlight Electricity Equipments Co.,Ltd..

Diesel battery is a start-up battery with a general service life of 3 years. If it has been used for more than 3 years, it is necessary to consider replacing it with a new battery. The battery voltage measured with a multimeter cannot completely accurately reflect the capacity and performance of the battery. Other tools such as battery internal resistance meter are required.

 

The above is the whole content of the maintenance case analysis of the Cummins diesel generator set that cannot start normally. I hope to inspire the majority of users. Jiangsu Starlight Electricity Equipments Co.,Ltd. is a manufacturer of professional generators, diesel generator sets, Cummins generator sets, Volvo generator sets, etc. The company has advanced testing equipment, excellent production technology, professional manufacturing technology, perfect quality management system, and Strong R&D technical strength. It can provide 15KW-2500KW various specifications of universal, automatic, four protection, automatic switching, low noise and mobile, etc., high-quality, low-energy generating sets to meet customer power needs, and can also meet users' different voltages and different frequencies, as well as the power supply system of multiple units connected in parallel, welcome customers to inquire. For more details, please contact us with sales@dieselgeneratortech.com


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