The fuel pump of the motorcycle EFI system is an important part of the fuel supply part, the performance of the fuel pump directly affects the power output of the EFI motorcycle engine is normal or not, today we will talk about the fuel supply part of the EFI system - fuel pump maintenance and fault analysis.

First, classification and structure of gasoline pumps

Efi motorcycles set environmental protection, fuel saving, good start and other advantages in one, deeply loved by the people. Nowadays, EFI motorcycles have gradually replaced the motorcycles in the carburetor era, and the fuel pump of the EFI system serves as an important part of the fuel supply system, which provides the high-pressure fuel required by the EFI system.

The fuel pump structure can be divided into two types according to the location of the installation: one is the external type, the fuel pump assembly is set outside the tank, such as the 2008 SUZUKI Suzuki Falcon fuel pump, this old fuel pump due to its poor heat dissipation conditions, large volume, heavy weight has been eliminated from use, belongs to the past tense. Instead, it is currently used quite widely reliable, lightweight fuel pump, that is, built-in fuel pump. The fuel pump is placed in the gasoline tank of the motorcycle, and the gasoline liquid in the tank is used to cool the heat of the fuel pump, so that the fuel pump can work for a long time to ensure the normal operation of the engine. At present, both pedal, straddle and domestic and imported motorcycles use built-in fuel pumps.

Harley fuel pump assembly structure diagram: filter, fuel pump, pressure relief valve, internal pipeline wiring harness

Second, the structure and working principle of gasoline pump

Motorcycle electric fuel pump is mainly composed of pump body, permanent magnet motor and shell three parts. After the permanent magnet motor is energized, it drives the impeller in the pump body to rotate, the fuel is sucked from the oil inlet, through the fuel pump inside, and then pressed out from the oil outlet to supply the fuel system with pressure.

When the fuel flows through the fuel pump, it also has a cooling effect on the armature of the permanent magnet motor, because the fuel pump motor is soaked in the fuel tank fuel, there is no air, and it is impossible to catch fire when the fuel pump is working. The motor of the fuel pump has a permanent magnet fixed to the housing, which is used to generate an electromagnetic force. The base of the gasoline pump assembly consists of a fuel pump power supply, a fuel sensor connector harness, a connector socket and a fuel output interface.

The gasoline in the motorcycle tank is pressure-free. Only when the ignition switch is turned on and the vehicle power is switched on, the motorcycle EFI system realizes self-test in the first time. The ECU provides the initial power to the fuel pump relay, and then the fuel pump in the motorcycle tank is switched on. The hum sound of the fuel pump motor working from the fuel tank (indicating that the fuel pump is working). The gasoline in the fuel tank passes through the coarse filter of the fuel pump, and first filters out the impurities and large particles of the fuel to avoid these impurities entering the fuel pump body and damaging the impeller. Fuel into the fuel pump motor, with the operation of the motor impeller, the fuel compression output 4-7kg or even higher pressure of fuel, this pressure value is the designer to consider the fuel pump motor with a long working process, the pump core wear will lead to premature decline in fuel pressure, the designer reserve the margin. The pumped fuel passes through the secondary filter element to further filter the fine particles in the fuel and protect the fuel nozzle in the EFI system from fouling. The filtered fuel enters the pressure relief chamber all the way through the pressure relief valve for pressure relief to ensure that the oil pressure of the fuel after pressure relief into the fuel injection system is always maintained within the range of 3-3.5kg. After pressure relief, excess fuel is returned to the fuel tank.

After pressure relief, the fuel pressure is maintained in the range of 3-3.5kg, and the pressure fuel is sent to the injector by the high-pressure oil pipe, and the ECU is injected according to the requirements of the engine working conditions. On the fuel pump assembly, there are two fuel filters, one is the primary coarse filter, usually the appearance can be seen, it is installed in the gasoline pump at the inlet of the plastic mesh shape of the filter. The other filter screen is the secondary filter screen, designed to be placed in the fuel pump assembly plastic parts of the internal oil circuit, the secondary filter screen is designed to protect the electric injection nozzle, to avoid the electric nozzle blocked by fine particles, and affect the spray atomization function. The secondary filter is stacked with paper similar to the air filter, which is used to ensure that the fuel filter is clean.

Three, the failure of the gasoline pump

The fuel pump of the motorcycle EFI system will produce the following faults in daily use:

1. Due to the long use time of the motorcycle, the quality of the gasoline filled in the use of the gasoline does not meet the requirements, or the frequent use of the gasoline filled with the low grade, resulting in the primary and secondary fuel filter blocking of the gasoline pump, and the decrease of the fuel flow resulting in insufficient fuel in and out, so that the fuel output pressure is reduced.

2, the failure of the fuel pump of the fuel system, the fuel pump motor is damaged (the fuel level of the fuel tank is too low to work for a long time, the fuel must be filled in time, otherwise it is easy to burn the fuel pump), and the fuel pump impeller is seriously worn, causing the output fuel pressure of the fuel pump to drop.

3. In the process of disassembling the gasoline pump during maintenance, the sealing ring of the oil pump and the sealing ring of the oil drain valve are not assembled in place, or the O-ring is damaged by assembly, resulting in a drop in the fuel pressure of the gasoline pump.

4, the fuel supply system circuit caused by the failure, the power is not in place (fuse blown, oil pump lead plug is not in place or open, plug-in poor contact) or fuel relay failure.

5, the fuel pump assembly in the pressure relief valve failure, caused by excess pressure relief.

6, due to the age of the motorcycle, or long-term storage, the fuel tank corrosion, the fuel tank internal treatment process is not good, causing the inner wall of the fuel tank corrosion, corrosion and blockage of the oil filter, gasoline supply is not on, resulting in insufficient fuel pressure of the fuel pump.

7. The oil pump output pipe of the gasoline pump assembly in the fuel tank and the oil pipe output interface are broken (such as the old golden wing, some Harley, and some Ducati models), and the oil leakage causes the fuel pressure to drop, resulting in the engine being difficult to start, the engine working abnormally or even unable to start.

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