I work at an injection molding machine manufacturer, and see some analogy that could work. At the heart of the molding machine is a 210 bar (roughly 3,000 psi) hydraulic pump. When oil gets dumped back to the tank, a breather valve relieves any excess pressure. The oil then gets filtered through a kidney loop.
In a similar fashion, can't the return line of the HPFP be connected to an intermediate breather box?
The box would have diesel fuel on the bottom, air on top (i.e. never full). On the top, there would be a one-way breather valve that can relief the pressure from pump return. On the bottom there can be a filter that cleans the fuel as it returns to tank. This could either be gravity-fed or driven by a small electric pump.
Once in a while the owner can drain the fuel in the breather box andreplace the filter.
This should keep any debris out of the fuel tank and avoid any problems due to high pressures from the pump return. In addition, the filter can be very cheap then.
Depending the maximum amount of fuel that can be dumped, the breather box can be sized accordingly. The only problem is that the engine compartment is already very stuffed...
I can sketch it up if anyone is interested.
James
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