First off, thanks to everyone on here for the volumes of information regarding fuel pump replacement. It helped out greatly with dropping the tank to tackle this job.

I pulled the unit out only to find the filter destroyed, but was amazed at how clean the inside of the 30+ year old tank is.

My question is, should I be able to blow air through all 4 lines on the unit with it out of the tank? I tried it yesterday and could only get air through 3 of the 4. I just didn't know if i should replace the whole assembly or just the pump/filter.

 

No , you should not be able to blow air through all 4 lines , the one you couldn't blow air through is the one that the pump actually pressurizes the fuel rail with . There is a one way check valve in the pump that won't allow the fuel to drain back to the tank when the engine is off , it's that check valve that keeps (or is supposed to) pressure on the fuel rail when the engine is off .