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Old 05-23-2020, 09:23 PM   #99
GonicGM
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Join Date: Mar 2014
Location: Rochester, NH
Posts: 168
Re: 1973-1991 Dual fuel tank systems theory of operation

I recently had my OEM Pollack valve completely fail to the point of requiring replacement. For decades it worked to the point of being passable. It really never had trouble switching to the left tank, switching to the right was finicky. When it did not switch completely, the gauge would over sweep clockwise and truck would starve for fuel. I would switch back and forth and to the point it finally read properly on the RH tank, the switch-over was full and complete. That process recently failed and neither tank would read properly but I could pull from the left, I just didn't know how much fuel in LH tank. Needless to say, time to change valve.

I went through and tested 9 or 10 valves I had with test on truck, wife inside, me underneath. One flat did nothing. All others you could clearly hear and feel the switching action. Most read properly on LH tank, RH tank gauge would over sweep clockwise. Only two passed the test 100%.

It seems a comprehensive test requires fuel gauge feedback. Most valves fail for RH tank selection. All but one valve felt and sounded operable on simple bench test, even the one just removed, however, such valve will not uncover ports for RH tank.

FYI
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