Why is My 2003 BMW 745Li Cranking but Not Starting After Valve Stem Seal Replacement?

It sounds like you're dealing with a tricky situation with your BMW 745Li. Given the fault code `285A DME: Variable Valve Gear - Monitoring, Servomotor, Bank 1`, it's likely that the valvetronic system is causing the intake valves to remain open, which could explain the lack of compression you're seeing. First, it’s essential to double-check all the engine grounds. A poor ground connection can affect the valvetronic motors, which draw significant current. Make sure the valvetronic motor is receiving sufficient power as well. Since you mentioned that you didn’t remove the eccentric camshaft, it’s a good idea to verify that everything is correctly positioned, especially the rocker arms. You should also consider performing a valvetronic calibration. Sometimes, disconnecting the battery can lead to a loss of calibration, even if you didn’t replace any motors. A scan tool is necessary for this calibration process, so if you have access to one, it could help you determine if the system can recalibrate without setting any new error codes. Regarding the eccentric shaft sensor, testing it with a multimeter can be a bit tricky, as you typically need a scan tool for accurate readings. However, if you can check the power and ground to the motors first, that might give you some insight. If you still have concerns, removing the valve cover on bank 1 to inspect the rocker arms again could be beneficial. After removing the valvetronic motor, check for compression in the cylinders to confirm whether the issue lies with the valvetronic system or if there’s something else at play. By following these steps, you should be able to narrow down the problem and hopefully get your engine running smoothly again.