Check out this great read by Paul Sneden of King Air Maintenance Academy.
I'm just posting this to dispel what appear to be some common misconceptions about what's going on with the King Air's fuel systems.
First, let's talk about icing and sumping in the fuel cells. Water presence in turbine aircraft isn't nearly as scary as it is in piston aircraft systems. Turbine engines happily swallow a significant amount of water without any noticeable burps in performance. That's not to say they'll run on water, but it's better to understand how water behaves in Jet A as opposed to Avgas.
As most folks know, water and Avgas don't mix. When you sump an Avgas aircraft, that's an essential task since the water tends to bind to itself, and can accumulate to a quantity that will indeed cause a piston engine to stop producing power. Another consideration is that an accumulation of water can cause corrosion concerns.
In Jet Fuel, water tends to jump into suspension as much smaller molecules and accumulations. This is why when turbine aircraft are sumped, the person doing it may not see water drainage anything like on an Avgas aircraft. To be effective, sumping should be performed after a period of sitting still, and BEFORE any disturbance, even like opening the cabin door and getting aboard. Any vibration tends to put any accumulated water that has settled to the sumps back into suspension. I tell techs that if you've pulled the aircraft out of the hangar, then sumping is mostly a waste of time.
That's not to say that water isn't present in Jet Fuel, but it lives in suspension. Enter Prist or Anti Icing additives. Contrary to popular belief, agents like Prist don't "absorb" the water molecules or make them combustible. They chemically surround the H2O, and essentially provide a thermal blanket that means the water will only freeze at a much lower temperature. You see, water molecules aren't something to fear in turbine engines, BUT ICE IS. In this case, think of ice crystals floating around, not blocks of ice.
When ice crystals pass through the Low-Pressure pump, and arrive at the firewall fuel filter, they can accumulate in the screen enough to block it off. Should that take place, there's a bypass in the filter that will open and allow fuel to pass through. That's indicated by a red button on top that will pop up if the filter went into bypass (and it will stay that way). I doubt that blockage will cause the pressure to drop to 10 psi. The switch mounted on the filter body (10 psi) is the indicator switch for low fuel pressure. Occasionally, a tech will find the filter bypass button up, but opening the filter reveals no contamination. That was ice, and it long since melted.
The next step in protection is the Oil to Fuel heat exchanger. That has nothing to do with cooling the oil but is in place to heat the fuel well into a temperature where any remaining ice crystals simply can't exist in solid state. Again, fine water droplets are of little consequence when going on through the High-Pressure Pump, the Fuel Control Unit, and on to the Nozzles to become part of the combustion process. To put this in perspective, there are turbine aircraft that actually use jet pumps to suck the fuel cell water from the lowest point in the system and add it to the fuel on the way to the engine! If you're ever in doubt whether your heat exchanger is warming your fuel, put your hand on the strainer bowl just forward of the FCU (after perhaps 15 minutes of operation). It will be quite warm to the touch. If it's HOT (you'll immediately let go...) that's a whole different area of concern regarding engine operations and Fuel Flow indicating.
Now, to speak to a Low Fuel Pressure Warning: Although this is well taught in type schools, it's worth reminding that the Annunciation/CAS for low fuel pressure is hardly any reason for the loss of engine power. The Low-Pressure Pump is simply a boost to ensure the High-Pressure pump can operate in all conditions without cavitation. The High-Pressure Pump is more than capable of operating on suction feed and keeping the engine purring along nicely until the pilot selects a backup low pressure source (Standby Pump or Crossfeed). In the 90s, there's not a standby pump available, so depending on location, altitude, etc. it may well be that finishing the flight leg on suction feed with the Low-Pressure indication on is the correct decision. The only concern about the High-Pressure Pump operating in suction feed is one of cavitation, so the areas of concern would be high power or high altitude.
Image: Beechcraft (IG)