BMW X5 E70 piezo injectors and return leakage
How do you test a piezo injector on an X5 E70 diesel?
The resistance between the injector terminals is about 170-180 kilohms on a healthy one, but resistance alone does not always reveal a fault. Also measure the insulation resistance between the connector pins and the body with an insulation tester of at least 250 volts, since the injector is driven with about 120 volts.
How do you check injector return leakage?
With the BMW diagnostic software, a bleed procedure is run in which the transfer pump is run for at least three minutes. The return line is blocked off, and the injector that leaks too much produces the most fuel. An exact leak-off test requires your own measuring equipment.
Why does a leaking injector cause a cold starting fault?
The leak-off prevents the rail pressure from rising high enough, so the cold engine cranks slowly and does not start. When warm, the high-pressure pump produces more pressure and the car starts better.
Why do the injectors fail, and does a new injector need coding?
Water runs from the leak points in the water trays into the injector connectors and causes rust and short circuits, so check the connectors and the sealing of the trays. A new injector should be coded, although the car sometimes works without it.