Thanks for the info guys. Your feedback raises a couple more queries. Firstly, my starter works whether the park brake is applied or off. Maybe it's been tampered with and modified to allow this to be the case. Even so, I prefer it this way because I've had (for one reason or another) an engine stall while in a potentially dangerous situation (e.g. halfway through an intersection or crossing a train line) and need to restart without having to come to complete stop. Secondly, the air is actually leaking out of two small holes opposite each other on the barrel of the small cylinder which goes into the front of the injector pump. This air is also still escaping with the parking brake applied. Methinks I need to get my hands on schematic diagrams of the air systems. Anyone know a site where they may be viewed? This cylinder was replaced last time under professional guidance with attention being paid to the shims between the cylinder and the pump etc. Care was taken not to alter the positioning and travel of the cylinder as its piston when actuated has to be precisely correct. Thanks again, Tony M