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

**hatzie** · 07-28-2018, 03:10 PM

If it was just one tank I'd look at the sender or wiring but this is the same on both tanks. More to the point it's exactly the same on both tanks...

What's the same no matter which tank is selected??? The fuel gauge and the sender wire from terminal B of the valve to the gauge.

Typical Fuel Sender Resistances were within ±3Ω or so on my test gauges from several different years:

E = 0-3Ω
¼= 26-32Ω
½= 42-48Ω
¾= 61-67Ω
F = 87-93Ω

¾ is less resistance than F. The only way to get less resistance in this circuit is for the wire insulation to be rubbed through and make an intermittent ground connection. That's unlikely to be repeatable over time.

I'd say it's probably the gauge itself.

07-28-2018, 03:10 PM	#23
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,912	Re: 1973-1991 Dual fuel tank systems theory of operation If it was just one tank I'd look at the sender or wiring but this is the same on both tanks. More to the point it's exactly the same on both tanks... What's the same no matter which tank is selected??? The fuel gauge and the sender wire from terminal B of the valve to the gauge. Typical Fuel Sender Resistances were within ±3Ω or so on my test gauges from several different years: E = 0-3Ω ¼= 26-32Ω ½= 42-48Ω ¾= 61-67Ω F = 87-93Ω ¾ is less resistance than F. The only way to get less resistance in this circuit is for the wire insulation to be rubbed through and make an intermittent ground connection. That's unlikely to be repeatable over time. I'd say it's probably the gauge itself. __________________ 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; 04-28-2023 at 06:27 PM.