Is there a fuel pressure switch that would operate similar to the inertia switch in that in the case of a significant pressure drop(a failed union or other fuel supply component) that it would cut power to the fuel pump?
I've never heard of a system like this being installed.
The more common one is an oil pressure switch that cuts the fuel pump. This makes sure there is oil pressure before the engine starts on cranking. Once running, it acts to cut the engine if oil pressure drops dangerously low.
Yes, it is used on N20 systems to close the nitrous and fuel solenoids if fuel pressure goes below a certain pressure level. It's called a Hobbs switch and you can get them with different fuel pressure ratings (say for carb or EFI) and some are adjustable. Problem on EFI is how to set it up to work when the engine is cranking and the pressure is just starting to build and so on. It is simply a way to break a connection (typically to ground) based on pressure.
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