Gates points out that that when technicians replace the timing belt in the Synchronous Belt Drive Systems (SBDS) on diesel models in this range, they often make the mistake of turning the high pressure pump, manually, in order to ensure that it is free running.
These are common rail injection diesel engines and rotating the high-pressure pump is not part of the recommended procedure. To do so, causes problems. In fact, the pump must be ‘pinned’ in order to prevent movement during the belt replacement procedure.
The high-pressure pump is timed and its performance is crucial to the SBDS. It must generate the correct pressure at the correct time. If it is not pinned during the belt replacement procedure, the pump generates excessive vibrations that will cause the tensioner to fail.
A consequence is that the bracket on the high-pressure pump becomes subject to increased stress and will crack. Once the tensioner and/or the bracket fails, the timing belt will fail and catastrophic engine damage is the inevitable consequence.
When maintaining an SBDS, always use the correct tools, which are often specifically designed for each system.