Diesel generators, as important backup power equipment, are widely used in industrial production, construction, communication base stations, hospitals, data centers, and many other fields. However, when a fault occurs in the diesel generator fuel system, it not only affects the normal operation of the equipment but may also lead to production stoppage, data loss, medical accidents, and other serious consequences. Therefore, understanding the common problems and solutions of the diesel generator fuel system is crucial to ensuring the stable operation of the equipment.
Fuel system circuit blockage is a relatively common problem in diesel generators. It is usually caused by air entering the fuel line, forming an air lock. When air enters the fuel system, bubbles form in the line, obstructing the normal flow of fuel and resulting in insufficient fuel supply. In this case, the generator set may experience difficult starting, sluggish acceleration, or even automatic stalling in severe cases.
In addition to air lock, pipeline aging, deformation, and blockage caused by impurities can also lead to circuit blockage. When fuel pipes become aged or deformed after long use, or when impurities block the pipes, the cross-sectional area of the flow path is reduced, resulting in insufficient fuel supply. Furthermore, clogging of the diesel filter screen and fuel filter element can also lead to insufficient fuel supply, thereby causing power reduction or difficulty in starting the generator set.
This type of fault can be checked on site. First, use the hand oil pump to build pressure, then loosen the vent screw. If bubbles overflow continuously and exhaust cannot be completed, then it can be determined that air has entered the fuel line. If there are no bubbles but diesel flows out weakly from the vent screw, this indicates that the line is blocked. Under normal conditions, when the vent screw is slightly loosened, fuel should be ejected out under certain pressure.
The way to eliminate this fault is to identify and replace damaged or aged gaskets, joints, or pipelines. When replacing parts, it is necessary to choose reliable components to ensure smooth fuel flow. At the same time, regularly check pipelines and filters, clean impurities, and replace aged parts in time to prevent fuel circuit blockage.
The fuel supply of diesel generators is crucial to the normal operation of the equipment. If the fuel supply of the high-pressure pump is improperly adjusted or parts are worn, problems of excessive or insufficient fuel supply may occur. When fuel supply is insufficient, the generator set will have difficulty starting, insufficient power, and reduced speed. When fuel supply is excessive, the generator runs at excessive speed, produces black smoke, and may even experience "hunting" or "overspeed."
Excessive fuel supply from the injection pump is mainly caused by incorrect adjustment. For example, if the maximum fuel supply adjustment nut is set too large, or the stop screw of the control lever is misadjusted, excessive fuel supply may occur. In this case, the fuel supply of the high-pressure pump should be readjusted to meet the requirements. The adjustment process must strictly follow the equipment technical manual to ensure fuel supply accuracy.
Insufficient fuel supply from the injection pump is mainly due to severe wear of the plunger pair. When the plunger pair is worn, its sealing performance decreases, leading to reduced fuel supply. In addition, weakened or broken delivery valve spring force, or the sealing cone of the delivery valve being lifted by dirt, will cause leakage and reduced fuel supply. In this case, the plunger pair and delivery valve spring should be replaced to restore fuel supply.
The fuel supply advance angle of the diesel generator injection pump also has an important impact on equipment starting and operating performance. If the advance angle is too large or too small, the generator will be difficult to start. Comparatively, it is even more difficult to start when the advance angle is too small.
When the fuel supply advance angle is too large, it first manifests as excessively high oil temperature, accompanied by high water temperature. Taking a single-cylinder diesel generator as an example, the adjustment method is: remove the high-pressure fuel pipe from the injector, rotate it at a certain angle to make the spherical hole of the pipe joint face upward. Place the throttle at maximum fuel position, slowly rotate the crankshaft, and observe the oil level at the high-pressure fuel pipe joint. When the oil just begins to rise, stop rotating the crankshaft and observe the mark on the flywheel. If the fuel supply mark on the flywheel has exceeded the reference line on the water tank but the oil level has not risen, it means that the fuel supply is too late (advance angle too small). At this time, shims should be removed to move the high-pressure pump backward. Generally, every 0.2 mm change in shim thickness will change the advance angle by 3°.
When the fuel supply advance angle is too small, it is manifested first by excessively high water temperature, accompanied by high exhaust temperature, while the oil temperature rise is not obvious. If the oil level in the high-pressure pipe has already risen, but the fuel supply mark on the flywheel has not yet aligned with the mark on the water tank, it means that the fuel supply is too early (advance angle too large). At this time, shims should be added to move the pump body forward. By adjusting the shim thickness, the fuel supply advance angle can be precisely controlled, ensuring normal startup and operation of the generator.
Delivery valve sticking is a relatively serious fault in diesel generator fuel systems. When the delivery valve sticks in the closed position, the valve cannot be lifted, and the high-pressure pump cannot supply fuel. When the delivery valve sticks in the open position, it cannot close, and diesel will continuously flow out when the high-pressure pipe joint nut is loosened. In either case, the diesel generator cannot start, and a running machine will stall.
The main cause of delivery valve sticking is unclean diesel, with dirt entering the high-pressure pump and delivery valve. When diesel contains impurities, these impurities enter the high-pressure pump and delivery valve, causing the valve to stick. In this case, clean diesel should be replaced, and parts should be cleaned, especially the delivery valve, which should be ground after cleaning. During cleaning, use professional cleaning agents and tools to ensure dirt is completely removed and the delivery valve is restored to normal operation.
The spray pressure of injectors also greatly affects diesel generator performance. If spray pressure is too high, the generator will produce knocking sounds, especially at low speeds, and cause starting difficulties and power reduction. If spray pressure is too low, poor atomization occurs, with no clear knocking sound, also leading to starting difficulties and power reduction.
Excessive spray pressure is mainly caused by an overly tight adjustment screw. When the adjustment screw is too tight, injector spray pressure increases. In this case, adjust the pressure to standard value on an injector test bench. Professional tools and equipment should be used to ensure pressure accuracy.
Insufficient spray pressure is mainly caused by wear of injector needle valve components, increasing clearance and reducing sealing performance. If wear is severe, new needle valve components should be replaced to restore spray pressure.
If the fuel system does not supply fuel, injector spraying stops, and the running diesel generator will stall and fail to restart. Common causes include low-pressure fuel line not supplying fuel, fuel feed pump failure, broken plunger spring, or plunger sticking.
This may be caused by an empty tank or blocked outlet, clogged diesel filter, fuel line leakage, or air lock. In this case, first check whether there is fuel in the tank. If not, refuel immediately. If fuel is present, check whether the outlet is blocked, the filter is clogged, fuel lines are leaking, or air has entered to form an air lock. Blocked outlets and filters should be cleaned or replaced, leaking lines repaired, and air removed to restore flow.
When the fuel feed pump fails, it cannot deliver fuel from the tank to the injection pump. In this case, the pump should be inspected and repaired. Check components such as the plunger spring and plunger. If the spring is broken, replace it. If the plunger is stuck due to impurities or scratches, replace the plunger pair and repair or replace the tappet.
When using diesel generator fuel systems, abnormal phenomena in the fuel circuit may appear complex on the surface, but in essence, they are nothing more than blockage, leakage, damage, or maladjustment. When encountering abnormalities, the section-by-section tracking method can be used, progressively narrowing the suspicious range until the fault location is identified.
For example, when "no fuel supply" occurs, first remove the carburetor inlet pipe joint, rotate the crankshaft, and observe the outlet fuel condition. If supply is normal, the fault is behind the line, in the carburetor. If not, the problem lies in the fuel passage, pump, filter, or tank, and should be checked section by section and repaired as specified.
If the generator fails to start, and turning the crankshaft by hand feels light with little resistance, and pouring a little fuel into the carburetor allows it to start but it stalls immediately, or the generator gradually stalls while running, then this indicates "no fuel supply" or "poor supply." In this case, remove the outlet pipe of the fuel pump, rotate the crankshaft or pump by hand, and observe fuel flow. If flow is normal, the problem lies in the carburetor; otherwise, the pump and downstream fuel line should be repaired.
If the ignition circuit sparks normally but the generator cannot start, the fuel system should be checked. Fuel system failures mainly manifest as empty fuel tank, blocked line, or pump damage. First, check the diesel filter (transparent disposable cartridge) to see if fuel passes through. If no fuel, check whether the tank contains fuel. If empty, refuel. If not, check whether the filter is clogged and the pump is functioning. If the filter is dirty, remove the outlet pipe and crank the engine to observe flow. If flow is good, check whether the carburetor inlet screen is clogged. If flow is poor, check the filter inlet. If flow is good, the filter is blocked and should be replaced. If flow is poor, the pump is faulty or there is blockage between the pump and tank.
The normal operation of the diesel generator fuel system is critical to the stability and reliability of the equipment. By understanding common problems and solutions, faults can be effectively prevented and eliminated, ensuring normal operation of the equipment. In practice, the fuel system should be regularly inspected and maintained, impurities cleaned, aged parts replaced, and all adjustments performed strictly according to the equipment manual. Only in this way can the diesel generator start and operate normally at critical moments, providing reliable power supply for production and daily life.
