Air in the fuel system. Install clear pipe from Injection pump to filter and observe for air in the fuel. Alternatively connect pipe from pump inlet to container of fuel (by-passing the rest of the system). If the engine
runs OK, then investigate fuel supply from filter to tank.
Crossed feed and return pipes.
Blocked return pipe
or return banjo bolts.
Injectors. If the misfire is noticeable at idle speed, place some rag or absorbant tissue aound one injector at a time, release the pipe nut at the Injector and listen for a tone change in
the engine. If you can pinpoint the cylinder with the misfire, remove the Injector for testing or swap Injector with another from a 'good' cylinder and see if the problem moves. If the misfire is still evident on the original cylinder carry out a compression/cylinder