Fuel Pressure Check (Hard Start)

WARNING: This page does not describe the selected car, but rather 37 other vehicles, including the 2005 BMW 760i, 2004 BMW 760Li, 2003 BMW Z8, 2003 BMW Z4, and 2003 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.

Run engine at idle then turn off. Note fuel pressure. Note fuel pressure again after 20-30 minutes. If fuel pressure decreases by greater than 7.2 psi (.5 kg/cm² ), turn engine on, wait for pressure to stabilize, then turn engine off and immediately clamp off intake line near pressure gauge with Clamp (133010). Note fuel pressure. Read fuel pressure again after 20-30 minutes.
If fuel pressure drops by less than 7.2 psi (.5 kg/cm² ), check for fault in fuel supply lines, in-tank supply hose, or defective non return valve in fuel pump. If fuel pressure again drops by more than 7.2 psi (.5 kg/cm^cm2 ), replace pressure regulator.