BMW E39 M57 injectors: correction values and return leakage
E39 530d: what do the injector correction values tell you?
Values exceeding ±2 are a sign that the injectors should be investigated. Compare all the values with each other: a value well in the negative can mean that another injector is well in the positive. Decide on replacement only after the return leakage test.
How is the M57 injector return leakage measured?
Disconnect the injector return lines and connect measuring cups to them. Let the engine idle for about 2 minutes and compare the injectors' quantities. The limit varies by source (20-25 ml), so ask the injector workshop for the exact limit. Also measure at about 1500 rpm.
What does a leaking injector cause?
A leaking injector lets fuel straight into the return line, so the rail pressure collapses and the engine may stall. A healthy injector delivers nothing into the return line. The injector is replaced or serviced at a diesel workshop.
Is the fault in the injector or its connector?
An injector code or fluctuating correction values can be caused by a poor contact in the injector connector. Check and clean the connectors before replacing the injector.