My dad has a ag diesel tractor. He has 2 250 gl above ground fuel tanks (unleaded and diesel). Gravity feed into whatever you are filling. Shut off valve on the tank and a nozzle similar to a gas station on the hose. Leroy (check my profile) was having major running issues. Would be fine for a while, then just quit, like you pulled the shut-off handle. Did the usual, changed filter. No difference. Drained tank, no difference, took tank off, drained, cleaned, washed, dried, back on tractor, fresh fuel, no difference. Etc., Etc. Finally took all tubing off everywhere from the tank to the injection pump and found a small bug carcass, just the exoskeleton bone structure. Reached the conclusion that it was living in the nozzle and went into the tank once at fill up. He now has a piece of screen hose clamped to the nozzle.
Just something else to consider. Especially for the non-filterers.