Fuel filter light

[japar]

I got about 2 gals of new oil+ hyd. fluid did a 50-50 mix filtered it and put it in the almost empty rear tank. When I switched to the rear tank the fuel filter light came on. Switch back to the front it goes off. I keep adding diesel to the rear, switch to the rear and light comes on switch back to the front the light goes off. The oil was new not waste. Truck runs fine both tanks. 94 idi turbo. Any clues why

 

[icanfixall]

Are you running a stock lift pump? It may be about ready to qiut on you. That or the mixed fuel is too heavy and causing a vacuum signal telling you the filter is plugged up. Thats what the filter lite works from. Vacuum in the fuel system to the injection pump.

 

[Ironman03R]

I have this problem off and on and I'm ready to put an electric pump on to see if that helps. I tried swaping mechanical lift pumps but that didnt change anything.