Multifuel truck in-tank pumps are getting fewer/ farther between, and costlier .. As mine fail and I ran out of spares, i first went to using 24v aircraft in-tank pumps.. Often the same maker, a similar design, somewhat cheaper, but they need time invested to retrofit the wiring and make it fit the existing truck cage.. They are not "plug & play" , they are getting hard to find too, and most of them are in "used" condition.. The gov't is no longer fielding trucks with a multifuel-style in-tank pump, thus pumps are not being made for the gov't .. Used decent pumps are also getting scarce unless you have parts of your own.
For a couple "i don't care if they stay 100% original" 5-tons, I installed a Carter 24v heavy-duty 3/8" inline pump ahead of the filter.. Of course on your M818 you will either need one pump at each tank with separate switches, or adapt just one pump into the main line between your tank selector valve and filter , and tie into your accessory switch load-side wire.... I don't have their part number handy but they come as a kit with a mount and vibration isolators .. Got them on e*ay.. The pump pressure (@14psi) and fast action makes up for the 3/8 inlet/outlet size of the pump .. They do a good job at filter changing time, which is the only reason I did it. Those two trucks sit very long periods and go through filters whenever put to work for a week straight.
In over 45 years of trucking I have never seen any 855ci PT-pump cummins engine , military or civilian, of any HP, that had an inline or in-tank pump .. I still have a few commercial 855's out in the yard (NTC230, 290, 315, 350) and ran a NTC400 for awhile .. The only time an in-line or in-tank pump is beneficial on a PT pump engine is at filter change time, most-especially the M809-series.. There are in-line hand primer pumps out there , usually with a spin-on filter base setup , if you consider other options ..
Cummins PT pumps, as-built , do not need pressure feed and probably is no better for it if it had pressure feed.. Adequate lubrication in the fuel is what they need today.. Lastly, always felt they should have an inline check-valve immediately after the filter(s) and at the fuel tank(s), but none of what ever saw or owned did.. .. For a very long time I have been meaning to try check-valves "someday when I get time."
