We've (dealer) Sold probably 200 L3301 and probably 150 L3901's. Of those, 2 have been in for DPF cleanings due to hired hands ignoring the lights and beepers and derating of the horsepower. I don't know how; but they did. Rest are all hood replacements and PM. Oh and two wire harnesses and one flywheel (that one was a doozie!)
Finally got one that failed. Of course at first, we know nothing of it's history. Hood up diagmaster and find 6 codes all pertaining to the fuel system, high rail pressure and low rail pressure among other things. Tractor won't start (turns over fine, just won't kick off) so we're suspecting a delivery issue. Checked tank and fuel quality, looks good. Checked electric pump output-good. Removed line from supply pump and WATER comes out, pure water. Weellllll....I think we have a problem. I had the service manager call the customer & explain what we found, and in the meantime I got in touch with folks who know these things better than I. It was explained to me that the old style mechanical injection is somewhat tolerant of water but INtolerant of air. Well common rail system is opposite. They're a little more tolerant of air, INtolerant of water. Turns out that the suction control valve is STUCK open, thus it won't build any pressure to start the engine. Pressure should be really high on these (a LOT higher than mechanical injection, up to 10x higher). Customer calls back & says that they got a bad batch of diesel. More like they got a bad batch of water from the diesel station and the water tank was topped off with a little diesel. Said they removed all the "fuel" from tank and replaced the filter with one they sourced from NAPA.
That pump is about $3000 or so and since the bore of the SCV was likely damaged, it's the best and only option. That $3500 is not counting labor.
replacing it is not fun, but not impossible. Remove hood, dash, meter panel, fuel tank, fuel tank support, sub tank, bracketry, hoses, lines, throttle valve assembly, fuel rail, EGR valve, intake manifold, then lift the pump out of the block. Took me about 6 hours, I think I can do it in half that now that I've done one. Basically like a newer diesel pickup. If you have to work on it, you simply start removing stuff until you get to the part that needs attention-and there's a lot to remove to gain access to a supply pump on an L01.
Kubota does not endorse any other filter other than their own and if it came down to doing a scan on the fuel, if they find dirt particles in the pump/lines post-filter and find that an aftermarket filter is installed, they can (and will) deny the repair. They haven't done this yet, but the dealers have been warned that it will start happening. They're already doing oil and coolant analyses. It's not that they're trying to find ways to not pay up, it's that they're trying to find out why things fail-and the analyses point them in a better direction, which helps them build better equipment. Likewise, as a dealer tech, we're the same way but we have to answer to Kubota just the same, ultimately they make the decisions.