As a backup power source or main power source, the starting reliability of
diesel generator sets directly affects the safety of electricity use. However, in actual use, the unit may have difficulty starting or even fail due to various reasons. This article deeply analyzes the common reasons why diesel generator sets are difficult to start from a technical perspective, and provides a systematic diagnostic idea to help you quickly locate the fault point.
1. Starting system failure: mechanical and electrical double bottlenecks
1. Battery performance degradation
Performance: Only a "click" sound is heard when starting, and the crankshaft does not rotate.
Reason:
The electrolyte level is too low or the density is insufficient (less than 1.28g/cm³ in winter).
Plate sulfidation causes the internal resistance to increase, and the cold starting current (CCA value) decays by more than 50%.
Detection: Use a battery tester to measure the voltage (no-load should be ≥12.6V, load ≥9.6V).
2. Starting motor failure
Performance: A sharp friction sound is emitted during startup, and the speed is slow.
Cause:
Carbon brushes are worn out (remaining length < 1/3 of the original length).
Electromagnetic switch contacts are burned, and contact resistance is > 0.1Ω.
Emergency treatment: tap the starter motor housing. If the speed is restored, the carbon brush or electromagnetic switch needs to be replaced.
2. Fuel system blockage: "thrombosis" from the fuel tank to the injector
1. Fuel line blockage
High-incidence areas:
Fuel filter: impurities accumulate and cause pressure difference > 0.5bar (filter element needs to be replaced).
Oil pump inlet filter: easy to be blocked by wax crystallization in winter (diesel below -10# needs to be used).
Detection: Loosen the injection pump inlet pipe joint, press the hand oil pump, and if the oil is not flowing smoothly, it is determined that the pipeline is blocked.
2. Injector stuck
Performance: The engine explodes but cannot continue to operate.
Cause:
Carbon deposition on the needle valve pair (ultrasonic cleaning + calibration of injection pressure is required).
Injector nozzle dripping causes the mixture in the cylinder to be too rich (injector assembly needs to be replaced).
III. Air leakage in the intake and compression systems: the "invisible channel" for power loss
1. Air filter blockage
Impact: Intake vacuum > 8kPa, resulting in black smoke from the engine and a 30% drop in power.
Handling: Replace the filter element every 500 hours, and shorten it to 250 hours in desert environments.
2. Poor cylinder sealing
Detection method:
Cylinder pressure test: Normal cylinder pressure ≥ 12bar, and it needs to be disassembled for inspection if it is lower than 8bar.
Leakage rate detection: Smoke from the crankcase vent indicates that the piston ring seal has failed.
Common faults:
Piston ring matching: Need to bore the cylinder and replace the ring.
Valve carbon deposits: Need to grind the valve seat ring.
IV. Environmental and operational factors: "external interference" that cannot be ignored
1. Low-temperature starting dilemma
Critical temperature: The freezing point of 0# diesel is 0℃, and the freezing point of -10# diesel is -5℃. If it is lower than this temperature, the fuel grade needs to be switched.
Solution:
Install a water jacket heater (preheat 4 hours in advance).
Use starting fluid (containing ether, the injection volume must be controlled to be less than 2ml/time).
2. Operational errors
Typical cases:
Starting with load: causes voltage to drop suddenly, triggering reverse power protection.
Frequent starting: continuous starting interval is less than 5 minutes, burning the starting motor.
V. Systematic diagnostic process
Preliminary judgment:
Listen to the sound: starting motor idling (battery failure), explosion sound (fuel system problem).
Look at the instrument: oil pressure alarm (lubrication system failure), water temperature is too high (cooling system problem).
Segment detection:
Fuel side: hand oil pump pressure → filter element pressure difference → injector atomization.
Intake side: air filter resistance → supercharger speed → intercooler temperature.
Mechanical side: cylinder pressure test → connecting rod clearance → crankshaft axial movement.
Data verification:
Use an oscilloscope to detect the starting waveform (battery voltage drop <10V is normal).
Infrared thermometer monitors exhaust temperature (single cylinder temperature difference >50℃ indicates abnormal combustion).
Conclusion
Diesel generator sets that are difficult to start should follow the troubleshooting principle of "power first, oil second, simple first, complex second". By establishing a standardized inspection process and combining professional tool diagnosis, the fault location time can be shortened by more than 60%. It is recommended that companies equip preventive maintenance kits (including battery testers, cylinder pressure gauges, etc.) and regularly train operators to master basic fault handling skills to ensure that the emergency power supply "starts with one button and provides continuous power supply".
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