Fuel Filter Light?

[Camarogenius]

How does the Fuel Filter light work? Yesterday, my fuel filter light came on at about 2000 rpm. As the rpm's dropped it went out, just came on right before I shifted.
Now, I'm aware of just how useless the Ford Dash is. Is this just another random quirk, or do I have a fuel issue?
The fuel filter was changed about 4200 miles ago, and I run B-11 from the farmers co-op. (FS)
So, what type of sensor activates this light?
Thanks guys.

 

[RKOCH]

It is a vacuum switch that comes on as vacuum increases. Also if the fuel pump is failing it will come on as the engine is trying to pull more fuel than the pump is pumping. Change the filter if that does not work put a lift pump on it.

 

[93turbo_animal]

Its probally the B-11 waxing up the filter I been having problems with mine try switching to staright D2 and heat the filter up to get rid of the wax