BMW X5 E70 diesel does not start or stalls: rail pressure fault
Why does an X5 E70 diesel not start when the rail pressure stays too low?
The rail is the diesel's common high-pressure line from which the injectors draw fuel. If the pressure does not rise, the car does not start or it stalls under load. The cause can be a worn rail pump, leaking injectors or a clogged fuel filter, which shows up in the supply pressure. A fault code does not always appear.
How do you find a leaking injector?
The injectors' return leakage, or leak-off, is measured, and injectors that leak heavily are replaced. Replacing only the high-pressure pump or filter, or cleaning the injectors, does not always remove the fault. The injector number in the fault code is only indicative, so the leakage is worth measuring.
The car does not start and the lights are on or the starter does not turn, what is wrong?
The starting current or the control unit supply can be interrupted by a loose connection, a rotted ground or an oxidised supply cable. Low voltage often creates additional fault codes. Check the engine ground and the cable connections before more expensive parts.
Is it normal for a cold diesel to wait a moment before starting?
Yes, the glow period can last a few seconds before the engine starts. The glow light does not necessarily come on even though iDrive shows a glow message. If starting takes minutes, the fault is real.