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CONTROL SYSTEM FOR FUEL INJECTION PUMPS VPX-3

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Control system for fuel injection pumps VPX-3
Control system for fuel injection pumps VPX-3


The VPX system is designed to test and regulate distributor injection pumps Bosch VP37, which work with the electronically controlled power systems of EDC compression- ignition engines (Electronic Diesel Control) used in passenger cars and vans.

In the EDC systems, the dose of the fuel injected by the injection pump is not mechanically adjusted by the accelerator lever, but by the electronic control device called a dosing actuator.

The VPX system can handle two types of dosing actuators:

  • inductive sensor of the actuator position called HDK
  • the potentiometer sensor of the actuator position called MES

During the pump test, on the table, the basic component responsible for controlling the pump in the car that is the EDC controller is missing. The VPX system takes over the function of the EDC controller and enables the simulation of the setting the fuel dosage during the regulation of the pump.

The VPX system has both, the functions of the setting device, which are needed to verify the injection pump flow as well as to check the feedback signals. The main feedback signal of the injection pump is the signal from the sensor of the actuator position (that is form the HDK or MES sensors), which informs the EDC controller about the real position of the actuator and thus the dosage.

The VPX system has five functions that help during the test and regulation of the injection pumps.

  1. Setting the actuator and the spark advance valve

    This function makes it possible to control:
    - the position of the actuator (injection dose) in the full range of its motion,
    - the spark advance valve,
    - the fuel shut-off valve (ELAB),

    and also the readout of:
    - the position of the actuator,
    - the position of the setting ring (for the HDK sensor),
    - readout of the fuel temperature sensor resistance

  1. Actuator resistance measurement

    This function checks the tractive resistance of the actuator.

    After starting this function, two phases of the dosing actuator control can be differentiated:
    - phase 1 - the VPX system uniformly increases the power of the PWM control signal which causes the movement of the actuator in the maximum position direction.
    - phase 2 - the VPX system uniformly reduces the power of the PWM control signal which causes the movement of the actuator in the minimum position direction.

    During these phases the readout of the dosing actuator takes place. Thanks to this information, it can be determined where there was the biggest tractive resistance or where it stopped.

    The uniform delocalisation as well as the uniform changes in the PWM signal mean that there is no seizure and that the movement of the actuator is proper.

    The power range of the control signal for both phases, and thus the range of tractive resistance of the actuator can be adjusted. However, a large value of the PWM and uniformly changing values of the position should be a sign that the resistance within the full scope of actuator movement is too big. In this case, it is recommended to use the function "Check the actuator".

  1. Checking the circuit continuity, test of the actuators

    This function checks the continuity of following circuits of the injection pump:
    - circuit of the coil of the dosing actuator,
    - circuit of the position sensor of the dosing actuator,
    - circuit of the coil of the advance spark ignition valve,
    - circuit of the coil of the fuel shut-off valve,
    - circuit of the fuel temperature sensor.

    It also executes tests of working components:
    - the dosing actuator,
    - the advance spark ignition valve,
    - the fuel shut-off valve.

    To test the continuity of each circuit, the VPX system is able to provide the answer whether the pump circuit properly responds to a specific test signal. When the answer of the circuit is correct, the VPX circuit classifies it as a continuous circuit that is the one without any breaks or short circuits.

    In the case of the fuel temperature sensor circuit test, the correct result does not give the absolute certainty about its operation throughout the full temperature range. Complete confidence can be obtained by checking the return signal from the sensor at different temperatures of its operation. This can be done by means of this function - "Setting the actuator and the spark advance valve".

    The test of working components makes it possible to check the movement of the dosing actuator, the advance spark ignition valve and the fuel shut-off valve. During these tests, the VPX system provides the adequate control of the test elements and the task of the mechanic is to determine whether a given working component is operating. You can check this by using a stethoscope. However, the sound of operation of these elements is loud enough to be heard with no additional equipment and is not a major problem.

  1. Check the condition of the actuator

    The result of performing the functions gives an overview on the condition of the actuator tested. The dosing actuator is set by means of a steady-rate signal. Under the influence of this signal, the actuator shall lean to the maximum position. If the actuator does not lean to the maximum position (does not hit the upper bumper), it means it is necessary to start the procedures connected with removing the seizures or obstruction blocking its movement.

    Successful implementation of the function (achieving by the actuator the maximum position) is the first step to check it for the tractive resistance. It is recommended that the next step is to perform a function - "Check the seizure of the actuator".

    The control signal, which is formed by the actuator during the execution of the function, has a different value for the actuator with the inductive sensor (HDK) and different for the actuator with the potentiometric sensor (MES). The VPX system includes model control signal values for both types of actuators, when they should reach their maximum position. They have been obtained on the basis of the results from the examination of a large number of actuators. However, if there is a need, the VPX system makes it possible to change the signal to the desired value.

  1. Actuator cleaning

    The function consists in generating a specific signal for the dosing actuator forcing it to move at different speeds in the full range of motion. The implementation of cleaning agents or the ultrasonic washer along with the actuator in motion, gives good results in removing contaminants and the tractive resistance without the need to dismantle.

    The PWM power signal of the control actuator and thus the scope of its movement can be freely adjusted. For this reason, the control signal can be chosen so that the actuator moves within the full range or only within a specific part, where there is a problem with smooth movement.

You are most welcome to see a few screenshots:

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Cost of delivery depends on the supplier and the country of destination.

Have a look at injection pump tester - TP-3.


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