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Old 06-18-2021, 09:39 PM   #118
hatzie
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Join Date: Oct 2008
Location: Wentworth, NH
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Re: 1973-1991 Dual fuel tank systems theory of operation

84 wouldn't have Fuel Injection GM started that on the 1987 trucks.

The mechanical fuel pump will deliver fuel at the proper pressure for your carburetor from whichever tank you select.

Change the switch, check for volts and ground at the plug, and then check the old valve operation before you do anything with the new valve. A fair percentage of the time the old valve will work fine.

From 1981 on GM stopped using the AUX and Main designations and got right to the point LH & RH. You should make sure the LH tank is selected when the switch is set to LH and RH when RH is selected.
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RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...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.
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