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Cause Iinvestigation Of Diesel Generator Sets Not Starting Normally

Mar. 08, 2022

Recently, Jiangsu Starlight Electricity Equipments Co.,Ltd. after-sales maintenance department received a repair request. When a user's Cummins diesel generator set was tested weekly in accordance with the diesel engine maintenance procedures, the diesel generator started smoothly, but then an ultra-high-speed alarm occurred and stopped. After inspection, all parameters of the checked diesel engine are normal, but it fails to start three times in a row. The control panel panel issues a low battery voltage alarm. The measured battery voltage is 12.3V, which is slightly lower than the normal float voltage (normal value is 12.8V). Jiangsu Starlight Electricity Equipments Co.,Ltd. immediately dispatched experienced after-sales technicians to conduct troubleshooting.

 

Troubleshooting Process and Analysis of Diesel Engine Can't Start Normal.

 

The after-sales personnel measured that the voltage at both ends of the diesel engine battery was 12.3 V, which was slightly lower than the normal voltage. The preliminary prediction of the fault was that the battery voltage was too low or the capacity was insufficient. After charging the diesel engine battery for 6 hours and then measuring, it shows that the battery voltage is 13.3 V, but the diesel generator still cannot start normally, so the battery reason is temporarily ruled out. The diesel engine control panel can issue the start command normally, and the parameters are in normal state, so the fault of the controller is eliminated.

 

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

 

First, confirm that the fuel in the diesel fuel tank is sufficient and the oil gauge shows the same value. Secondly, check the state of the oil circuit to confirm that the oil circuit is smooth. Finally, check the fuel injection system, open the high-pressure fuel pump outlet pipe to start the oil engine, and find the fuel outlet of the fuel pump. If there is no oil output, the fuel cannot be delivered to the combustion chamber of the engine, resulting in the diesel engine not being able to start. Through the above investigation and analysis, it is preliminarily determined that the diesel engine cannot be started normally because the high-pressure fuel system of the Cummins diesel generator does not supply fuel.

 

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

 

diesel engine


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

 

By consulting the relevant technical data, it is known that the working power of the speed control controller comes directly from the diesel generator battery. When the battery capacity of the diesel engine is insufficient, the battery voltage is low at the moment when the diesel engine starts, and it cannot provide enough power to the speed control controller. The voltage output from the actuator to the electromagnetic actuator is lower than 10 V, and the solenoid valve cannot be opened normally, resulting in the inability of the fuel to be delivered to the engine combustion chamber, thus causing the diesel generator to fail to start normally, and the voltage of the speed controller measured at the moment of starting is 10.9 V.

 

So far, the reason why the Cummins diesel generator set used by the user could not start normally has been identified, and the direct reason is that the battery capacity is insufficient. Because the battery has been used for a long time and the capacity is seriously reduced, the voltage at the moment of starting the oil engine is low, and the required voltage value cannot be provided for the solenoid valve to work. As a result, the solenoid valve cannot be opened normally, and the fuel cannot be delivered to the combustion chamber of the engine, resulting in the failure of the oil engine. start up.

 

Summarize:

The direct reason that the Cummins diesel generator set cannot be started is the insufficient battery capacity, but the process of determining the cause is long. First, measure the battery voltage with a multimeter. Secondly, after the battery is charged, the voltage across the battery is measured by a multimeter, and the result is within the normal range, and the cause of the battery is ruled out. Finally, the diesel generator set had an overspeed phenomenon during the first failure, and the oil engine had an overspeed warning, so more attention was turned to troubleshooting the fuel system.

 

Jiangsu Starlight Power reminds:

Diesel engine batteries are start-up batteries with a general service life of 3 years. If they are used for more than 3 years, consider replacing them with new batteries. The battery voltage measured by a multimeter cannot fully and correctly reflect the capacity and performance of the battery, and other tools such as battery internal resistance tester are needed.

 

The above is the entire content of the maintenance case analysis of the Cummins diesel generator set that cannot be started normally. I hope to inspire the majority of users.

 

Jiangsu Starlight Electricity Equipments Co.,Ltd. is one of the earliest manufacturers of generators and diesel generator sets in China. The company was established in 1974 and the company occupies an area. With an area of 86,000 square meters and a building area of 45,000 square meters, it has 64 sales and service departments across the country to provide users with one-stop service of design, supply, debugging and maintenance at any time. Welcome customers to come to consult and visit. Looking forward to your inquiry, please send email to us for details sales@dieselgeneratortech.com


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