Stovies wrote:I've noticed that I have air in the return line. Is this normal.
There shouldn't be air in the return. To have air in the pipes, there must be a leak letting air in somewhere. This could be before the injection pump, in which case there would be bubbles all the time the engine is running. Any of the joints could be at fault, including the fuel filter. They can be difficult to find, but you just have to persevere. If you get bubbles only when first started the leak may be on the return line somewhere, as with the engine running this pipe is not really under suction. Principal culprits here are the back leakage braided rubber pipes on the injectors, and that little rubber cap on injector 4. (Change these anyway, they are only a couple of quid).
There should be a length of translucent pipe on the inlet to the IP so you can check for bubbles. If not, best change it to translucent.
Be thorough. Best of luck.