K:

1) Disconnect the return line at the Fuel Distributor (FD); attach a hose so that fuel can be discharged into a container. Return flow should be 1 liter in 30-45 seconds.

2) If insufficient flow, remove the inlet fitting at the FD, remove the screen & check it for clogging.

3) Yes, the injection nozzles do have ~40psi check valves, however, after sitting for a prolonged time they may be clogged. They can be cleaned.