Re: Return diesel fuel to the tank?
All injector pumps HAVE to have a 'leak off' pipe.
It may do but does not HAVE to return to the tank.
It may return to the fuel feed pipe anywhere between the tank and the inlet side of the low pressure 'lift' pump.
So what the Bounty guy said might be correct.
Now as the qty of fuel that leaves the high pressure pump through the leak off line, is small, much less than the qty actually consumed by the engine using it as a way of polishing the fuel is a non starter. [ There is an exception, the old CAV rotary pumps did return significant amouts. I am not sure if it would be enough to 'polish' fuel though.
Ex diesel mechanic and instructor.