Function check with diagnosis instrument Component description Explanation of Input and Output menu Control unit The Input and Output menu shows the components which supply signals to the control unit and their sta- tus, by means of ones and zeroes. Using this menu, faults in the internal function of components or their cables, connected to the control unit, can be identi- fied. Control unit, (16) The control unit is located by the fuel filter. There is a 42 pin sealed connector at the rear of the control unit for connecting the cable harness. The con- trol unit cables are protected by flexible plastic hoses.
When the Input and Output sub-menu is selected, by pressing the execute button , two lines of ones and zeroes are displayed, sub-divided into two groups of eight, one line for inputs and one line for outputs. A hose connection for measuring the charge pressure is located underneath the control unit. The figures represent the following components, start- ing from the right. (Please refer to the “Sub-menus for Inputs and Outputs“ illustration). The control unit, which is the central section of the EDC system, receives continual information from sen- sors located on the engine and controls.
The informa- tion is processed by the control unit, which sends sig- nals to the electromagnetic acutator. The actuator then controls the amount of fuel supplied under each load- ing. Inputs: 1. Function button, “Calibration“ 2. Function button, “Start“ 3. Choice of “Regulator mode” 4. Not active 5. Not active (red) 6. Not active (blue) 7. Function button, pre-heating 8. Not active 9–16. Not used. Outputs: 1. Main relay 2. Starter relay 3. Actuation solenoid, control rod (=1 at working cycle > 0%) 4. Not active 5. Not active 6. Not active 7. Not active 8. Pre-heating relay 9.
Lamp for function button, “Regulator mode” (green) 10.Temperature warning – OUT 11.Lamp for function button, “Diagnosis“ (green) 12.Not active (red) 13.Not active (blue) 14.Not active 15.Not active 16.Not active EDC system control unit The control unit also has the task of monitoring the system and generating fault codes when any faults oc- cur. Limits for the TWD740VE Alarm values Highest permissible values of charge air temperature, coolant temperature etc. If the alarm values are ex- ceeded, the system reduces the fuel value until the value falls within the permissible value again. The en- gine must be re-started to get normal power back.
Sub-menus for Inputs and Outputs The following alarm limits are pre-programmed into the control unit: Highest permissible charge air temperature ............................................120 ° C Highest permissible fuel temperature ........... 85 ° C Highest permissible coolant temperature on/off: ..................................................... 101/98 ° C Highest permissible engine speed: 175 kW .....................................................2800 rpm 203 kW .....................................................2600 rpm Highest permissible frequency .................. 1875 Hz Lowest permissible frequency ......................
30 Hz Highest permissible charge pressure, please refer to the Max curve in the diagram. Diagram for charge pressure, TWD740VE NOTE! Pressure is measured as absolute pressure. 36 17