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Old 10-17-2018, 03:42 PM   #1
jcondo
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duel tank switch in cab

Does anyone know if they located the switch somewhere other then the dash next to the ash tray?
I have a 77 chevy K10 with dual tanks, but I cannot find the switch inside the cab. There is no holes in the dash that show where it could have been located at. I'm also not cutting/drilling a new hole just for a newer style of switch.
The previous owner said something about it being on the floor and removing it for some reason, but he is on vacation for the next 6 months and I have no way to contact him until his return.
Thanks for the info as always.
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Old 10-17-2018, 03:58 PM   #2
chrismoore701
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Re: duel tank switch in cab

not 100% sure, but I want to say I have seen a valve style switch that you twist located on the floor between the door and the seat. Push on the carpet and see if there is a hole there
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Old 10-17-2018, 06:09 PM   #3
jcondo
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Re: duel tank switch in cab

Thanks Chris,
I have not yet gotten to the point of doing the interior. I was gonna start on getting the left side fuel tank to work but needed to know the correct type of selector and location. When I do get there ill repost on here.
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Old 10-17-2018, 07:07 PM   #4
Tarm
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Re: duel tank switch in cab

iif you relocate the switch I recommend keeping it to the left of the driver. Keeps ignorant or curious passengers from pressing it and ending up running out of fuel?!? That is more than a minor inconvenience with a diesel with a mech fuel pump. It could kill a pair of bats and or a starter before you get it restarted on the side of the road. Also another good reason to never let a tank go below 1/4.
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Old 10-18-2018, 06:28 PM   #5
hatzie
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Re: duel tank switch in cab

Since you don't have a square factory hole in the dash you can put the switch anywhere you darn well please. Moving it to the LH side of the dash is an excellent idea. Rather than cut a square hole for the GM rocker switch just drill a 1/2" hole and use a toggle switch...

If your solenoid valve is working you can use a six terminal DPDT toggle switch on the dash. Try to find an ON-ON switch rather than an ON-OFF-ON... You can use either but obviously ON-ON is more intuitive.
Clip off the outer 45° terminal corresponding to the blocked hole in the stock 1973-1980 switch plug that GM used as a key.
You can get Generic DPDT toggle switches with six 1/4 disconnect terminals from McMaster Carr and many other outfits. I'd get one that carries a minimum of 15A continuous. 20A or 25A would be better.

If you need to run the 1981 and later motorized valve you can get a four terminal Polarity Reversing toggle switch with 1/4 disconnect terminals that can use the same connector shell as the 73-80 switch.
A Polarity reversing ON-OFF-ON toggle switch that will carry 25A operating current is Cole Hersee 55046. Waytek Wire carries them.
https://www.waytekwire.com/item/4426...BoCeO0QAvD_BwE

Keep in mind that the Polarity reversing toggle switches you can buy have a centre off position. This can be useful on 1987 & later TBI fuel pump systems as a theft deterrent... Setting the switch to the off position shuts off power to both fuel pumps til you select one or the other and it's not easy for a thief to find.
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Last edited by hatzie; 10-18-2018 at 06:35 PM.
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Old 10-18-2018, 10:07 PM   #6
jcondo
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Re: duel tank switch in cab

Thanks everyone for the info.
Upon talking to the P.O. and doing more digging around in the truck this after noon, I have found out that it did not come with a factory auxiliary tank.
P.O. and RPO codes confirmed this, he claims to have added an aftermarket fuel tank on the drivers side. He says that it never had an actual duel tank set up and that the added one just pumped over to the original tank on the passenger side.
So depending on what I find out with the passenger side tank I may just eliminate it and patch the hole when I get the rust repaired, or ill figure out a way to make it useable.
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Old 10-19-2018, 08:08 AM   #7
hatzie
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Re: duel tank switch in cab

Do you travel and tow enough to make adding the plumbing and electrical to your truck worthwhile? Only you can answer that question.

Adding the plumbing for NL2 dual tanks isn't that difficult.
Even the wiring isn't too tough.

Stock 1977 solenoid valves are obsolete, hard to find, and EXPENSIVE
Since you're essentially starting from scratch there's only one sane way to go... the system that GM used from 1981-1991... the Pollack Motorized Valve.

There's a member here that makes custom NL2 harnesses that include a new 65PSI 81-91 motorized Pollack valve in various configurations with relays for EFI and no relays for carburetors. I've never done business with him but others have. You can likely ask him for the proper connector and wire lengths to reach your chosen switch and location.
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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...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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Old 10-19-2018, 10:59 PM   #8
jcondo
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Re: duel tank switch in cab

Thanks hatzie for all the tips and info.
The only reason I wanted to put the tank into service was to take it back to original, so once I get it out and start driving it ill see if I need a 2nd tank or not.
Thanks again.
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