Re: Erratic Fuel Flow (FF) reading with alarm
What if it's not a nuisance alarm, but an indicator of a bigger issue?
Is it possible you're seeing some vapor bubbles forming in the line during low power descent (classic vapor lock danger zone)? Under low power, the engine driven pump would still keep enough fuel in the carb bowl for operation even with vapor bubbles, until the situation became extreme. As soon as you increase power the fuel level in the carb bowl will drop and pump is now not only refilling the fuel bowl, but also displacing the vapor in the lines. This could possibly exceed 20 gph for a few seconds, triggering the alarm. As soon as the lines are full of cool fuel again, flow stabilizes and the alarm will shut off, just like you're seeing. An injected engine would stumble from the fuel pressure fluctuations, but a carb'ed engine will be able to take it for a few seconds with no indication to the pilot due to the fuel bowl quantity.
Do you have a cooling shroud on your engine-driven fuel pump? What about heat insulation on the fuel lines forward of the firewall? This may not be a fuel flow sensor problem.