The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 1973-1991 Dual fuel tank systems theory of operation

**hatzie** · 01-05-2018, 08:44 AM

It's real easy to swap the returns such that you're filling the un-selected tank from the engine fuel return.
I always double check the hoses on the LH side and RH side of the valve are coming from the same sender hoses. Green and Blue painters tape makes good assembly identification.

I'm not saying it's impossible to leak past the return o-rings on the valve shuttle but it would be very unusual.
Swap the return hoses on the tank side of the valve so the supply and return from each tank are on the same side LH supply & return in the LH side of the valve and RH supply and return in the RH side of the valve instead of opposite sides. This will likely fix the problem. Then you can take the replacement parts back to the store.

01-05-2018, 08:44 AM	#7
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,975	Re: 1973-1991 Dual fuel tank systems theory of operation It's real easy to swap the returns such that you're filling the un-selected tank from the engine fuel return. I always double check the hoses on the LH side and RH side of the valve are coming from the same sender hoses. Green and Blue painters tape makes good assembly identification. I'm not saying it's impossible to leak past the return o-rings on the valve shuttle but it would be very unusual. Swap the return hoses on the tank side of the valve so the supply and return from each tank are on the same side LH supply & return in the LH side of the valve and RH supply and return in the RH side of the valve instead of opposite sides. This will likely fix the problem. Then you can take the replacement parts back to the store. __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful. Last edited by hatzie; 01-05-2018 at 05:49 PM.