Add: Mechanical&Electrical Industry Zone,Yuhuan,Zhejiang,China
Fuel pump as one of the key components of the fuel system, Fuel Pump we should understand the fuel pump control circuit. Electronically controlled fuel injection system The requirements for the fuel pump are: When the ignition switch is turned on, the fuel pump turns 2-3S to establish the working oil pressure before the motor vehicle, or the fuel pump is turned when the vehicle is started. If the engine does not rotate, the ignition switch is open Position, fuel pump does not work. Fuel pump rotation, depending on the fuel pump to the external power supply, in general, the fuel pump speed is constant, the output oil volume unchanged,Fuel Pump but the engine high and low speed when the oil supply is different, so in some models , The design of the fuel pump high and low speed, so that the amount of fuel pump output oil to meet the needs of different engine conditions, fuel pump external power and fuel pump high and low speed changes, by the fuel pump control circuit to achieve of. Fuel system control circuit, is the electronic control system design changes in one of the larger circuit, so to master the principle of the circuit and testing must grasp the circuit analysis methods and circuit analysis ideas.
The main relay is installed in the fuse box in the cabin, Fuel Pump it is the main control part of the electronic control system, the relay has four terminals, terminal 1 and terminal 3 connected to the electromagnetic coil, with a multimeter resistance file, measuring terminal 1 and terminal 3 normal Should be conductive, such as not through the side to prove that the coil is broken, the terminal 2 and the terminal 4 connected to the electrical normally open contacts with a multimeter resistance file measuring terminal 2 and terminal 4 should not pass normal, as shown in the contact, with the battery to the terminal 1 and terminal 3 power, Fuel Pump the normal relay should produce a suction sound, and then use a multimeter to test terminal 2 and terminal 4 should pass, or should replace the relay.
When the engine is not running, even if the ignition switch is in the open position, because there is no air intake, the air flow meter measuring piece is not deflected, Fuel Pump the fuel pump switch contact is disconnected, so the coil L1 is not energized, the relay contacts can not be closed, the electric fuel pump also It is not running; when the engine is running, the inlet flow deflects the measuring piece, the fuel pump switch contacts are closed, the coil L1 is energized, the relay contacts are closed and the fuel pump is running. A capacitor is also connected in parallel to the circle L1. When the engine deceleration or high load low speed operation, the intake pulsation may cause the measuring piece to close and cause the fuel pump switch contact to disconnect, Fuel Pump the coil L1 power. The capacitor can be discharged to the coil L1 at the moment when the coil L1 is de-energized, keeping the relay contact closed, preventing the electric fuel pump from stopping and keeping the oil pressure stable.