The tolerances given to the injectors on manufacture mean that the actual injected volume of fuel deviates slightly from the theoretically calculated volume of fuel. These injection volume tolerances are determined for each injector across the entire operating range following manufacture by measurements at the suppliers. From these measurements, two adjustment values are generated for each injector.
During vehicle assembly, after installation of the DME control unit, the adjustment values of each installed injector are stored in the DME control unit. The adjustment values are allocated to the individual cylinders according to the installation of the injectors.
The injection volumes calculated by the DME control unit are corrected by these adjustment values, thus improving the exhaust emissions.
The service function can be used to change the adjustment values of the injectors in the control unit or store new values.
The adjustment values are printed in two blocks each with three digits on each injector (see graphics below). The inscription can be located either on the plastic bracket or the metallic upper part.
Graphic 1: Example of inscription of the adjustment values on the plastic bracket
Graphic 2: Example of inscription of the adjustment values on the metallic upper part
Important:
If injectors are renewed or replaced,
it must be ensured that the printed adjustment values
of each injector are assigned to the right cylinder in the DME (digital engine electronics) control!
The injectors must be removed if the adjustment values cannot be read out while they are fitted.
If the engine
has already been operated with the injectors, the seal must be replaced before installation.
Ensure that the repair instructions are followed!
Important:
Conversions within the DME control unit mean that the last position of the adjustment values can differ slightly after saving the entered values. There is no input or control unit error!
Important:
If the DME control unit has been replaced, the adjustment of the injectors must also be carried out so that the adjustment values of the fitted injector are stored in the new control unit! Otherwise, either rough engine operation is possible or the engine might not start.
Note:
For cylinders where no new adjustment value is entered, the existing adjustment values
are retained in the DME control unit.