
Electronic fuel pump, immersed in fuel tank levelly, is fed electricity to through fuel pump relay by battery. This relay’s
switch-on/off is controlled by ECU. When the key in ignition switch is turned to the "Ignition" position, the electronic fuel
pump may not be always powered on. When the key is turned to the "Start" position, ECU will switch on the fuel pump relay,
and the electronic fuel pump will immediately start to continuously supply fuel. When the key is turned from the "Start"
position to the "Ignition" position, it will continue its running. At the moment, it is not the same as the previous case that the
key is placed to the "Ignition" position before its start. This is because ECU can make the fuel pump relay switch on only if
the engine is running. Once the engine stops, the fuel pump will immediately stop its fuel supply.
Electronic fuel pump is made up of pump, electric motor and pump cover (See Fig. 209).
Electric motor consists of a permanent magnet and an armature. On pump cover there are electric contact, connector for
outlet pipe and check valve. Check valve is used to keep some residual pressure within the fuel system after the electric
fuel pump stops running so that it restarts. Without check valve, the positive-pressure fuel will flow back into the fuel pump
and fuel tank resulting in system decompression, so the fuel within the fuel system will be easily vaporized due to high
temperature to produce vapor bubbles and then cause vapor lock. This is a structural fault that is necessarily avoided within
fuel system.
In the fuel pump case, both pump and electric motor are always surrounded by fuel therein. This can satisfy lubrication
requirements of parts and heat emission requirements of electric motor, along with improvement of electric motor
efficiency. In addition, no complex sealing device is required between pump and electric motor.
Fig. 208 Fuel supply system based on multiport injection
1. Fuel tank 2. Electronic fuel pump 3. Fuel filter 4. Fuel deliver pipe (fuel rail) 5. Fuel injector 6. Fuel-pressure regulator
Negative pressure in ntake pipe
96
Содержание JL481Q
Страница 1: ......
Страница 9: ...5 Fig 3 Components Assembly Drawing of MR479Q MR479QA Engine ...
Страница 10: ...6 Fig 4 MR479Q MR479QA Engine and Its Power System ...
Страница 11: ...7 Fig 5 Assembly Drawing of Engine and Its Auxiliaries MR479Q MR479QA ...
Страница 12: ...8 Fig 6 Electronic Control Fuel Injection System in Engine MR479Q MR479QA ...
Страница 13: ...9 Fig 7 Front view of Engine JL481Q MR481QA ...
Страница 14: ...10 Fig 8 Sectional elevation of Engine JL481Q MR481QA ...
Страница 15: ...11 Fig 9 Electronic Control Fuel Injection System in Engine JL481Q MR481QA ...
Страница 21: ...17 Fig 13 Exterior Feature of JL481Q Engine Power Me N m Torque Pe Kw ge g kwh Fuel Consumption Ratio ...