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Old 03-25-2020, 11:48 AM   #83
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

LWB could be either a 16 or 20 single tank. I've owned both.
I doubt SWB has the room for a 20 gallon tank.

Not sure someone that went to the trouble of ordering NL2 and the 8' bed would order a pair of 16 gallon tanks. I doubt a dealer would order something odd like that for stock either.

Honestly you can fit the 20gallon tank with the 16 gallon straps so if you have a LWB truck just get the 20 gallon tanks and have done with it.

Quote:
Originally Posted by Hart_Rod View Post
Somebody had two of the connectors plugged in wrong! Both of these connectors are by the LH tank and the wire colors are very similar (see diagram below). It's crazy that everything still worked (other than the RH tank reading incorrectly). I plugged the connectors in correctly and everything works perfect now.
Something that occurred to me that needs to be said.

The NL2 dual tank harness is an add-on to the production fuel system wiring that plugs right into the existing single tank sender/pump connection on the standard harness. Probably for ease of assembly and reducing the number of electrical harnesses to select on the line. This also would allow a dealership or customer to add it if desired but I doubt that was part of the GM thought process.
Someone swapped the standard production fuel tank connector and the connector from the valve. Probably when doing service on the LH tank.

I have several colors of 3M Super 33+ Electrical tape that I wrap on harness wrap ends with plugs that can be interchanged... to avoid the mistake you discovered.

The LH fuel pump was running dead head to the valve when the RH tank was selected. That can't be safe. Not sure what mayhem you avoided by fixing this but it's all good now.
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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.

Last edited by hatzie; 03-25-2020 at 12:22 PM.
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