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#1 |
Senior Member
![]() Join Date: Oct 2009
Location: Godley, TX
Posts: 17,963
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72 C20 with an interesting previous owner NL2 aux tank modification
When I first bought this 72, I assumed a po had just replaced the NL2 fuel gauge selector switch with a standard toggle switch. But it really didn't matter since the floor-mounted fuel tank selector valve was long gone anyway. But as I looked closer, I noticed an electrically-actuated fuel tank selector valve was under the cab. Hmm - so THEN I wondered if the po sacrificed the ability to choose which tank level to display on the fuel gauge and wired in an electric tank selector valve in its place. To my surprise, when I pulled the switch to replace it with the standard NL2 rotary fuel gauge selector, I discovered a 6-terminal switch that in fact did all of the above - something I always secretly wished GM had done from the very start (i.e. flip the dash switch to aux and it would automatically change fuel tank selection AND fuel level sensor source for the fuel gauge). Anyway, it was a pleasant surprise (that I'll probably get rid of for the sake of originality - or, more likely, mount out of sight and put a dummy NL2 rotary switch in its place). Thought I'd share - never saw one of these before, but always wished there was such an animal from the factory. Now, if I could just get Fed Ex to stop playing soccer with the fuel tanks I order from Classic Parts.. Not only was the filler neck bent and pushed into the tank, the other corner was also rolled over completely from being dropped or something like that. I did chat with Classic Parts and a new tank is on the way, so no complaints about customer service
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#2 |
Born Psycho
![]() Join Date: Feb 2001
Location: brentwood,cal,usa
Posts: 4,881
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I just gave an factory auxiliary tank to a fellow board member that had the same electric switch as yours , the tank was given to me by another board member several years back . i don't remember what switch was in the dash but i assumed someone had added the electric switch from a square body.
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jerry moss 72 cheyenne super K20- tilt,tach,vacuum,speedwarning,buckets,shoulder belts,am/fm,tow hooks,bumper guards,toolbox,aux. fuel tank,posi front and rear,plus other goodies!!! SOLD 69 suburban K20-tilt,tach,vacuum,speedwarning,buckets,shoulder belts,am/fm,4 inch all spring lift,4 speed, 14 bolt full floater, dana 44 HD,warn winch,posi front and rear,tow hooks,plus other goodies. 73/80 chevy/gmc K20 SB400,turbo 400,205,tilt,a-c,gas hog. 77 K/5 cheyenne blazer-daily driver/beater. SON HAS IT NOW BRENTWOOD,CALIFORNIA |
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#3 |
Senior Member
![]() Join Date: Oct 2009
Location: Godley, TX
Posts: 17,963
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Re: 72 C20 with an interesting previous owner NL2 aux tank modification
Thanks Jerry - do you or does anyone know if that is indeed a standard squarebody fuel selector valve? Would really like to confirm - if so, I might just incorporate it (ie if I know there’s a chance of finding a replacement if it ever fails).
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#4 |
Born Psycho
![]() Join Date: Feb 2001
Location: brentwood,cal,usa
Posts: 4,881
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I honestly don't know what the switch originally came from. i had to change the switch on my 73 way back when-but that was over 40 years ago and my feeble old brain can't remember that far back.
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jerry moss 72 cheyenne super K20- tilt,tach,vacuum,speedwarning,buckets,shoulder belts,am/fm,tow hooks,bumper guards,toolbox,aux. fuel tank,posi front and rear,plus other goodies!!! SOLD 69 suburban K20-tilt,tach,vacuum,speedwarning,buckets,shoulder belts,am/fm,4 inch all spring lift,4 speed, 14 bolt full floater, dana 44 HD,warn winch,posi front and rear,tow hooks,plus other goodies. 73/80 chevy/gmc K20 SB400,turbo 400,205,tilt,a-c,gas hog. 77 K/5 cheyenne blazer-daily driver/beater. SON HAS IT NOW BRENTWOOD,CALIFORNIA |
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#5 |
Registered User
Join Date: Jan 2011
Location: Redmond, OR
Posts: 758
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Re: 72 C20 with an interesting previous owner NL2 aux tank modification
It looks like the factory squarebody switching valve from a mid to late 70s square.
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68 Chev C20- son has it now 83 K20 - bought from son 70 C20 - in progress |
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#6 |
Senior Member
![]() Join Date: Oct 2009
Location: Godley, TX
Posts: 17,963
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Re: 72 C20 with an interesting previous owner NL2 aux tank modification
Thanks guys!
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#7 |
Senior Member
![]() ![]() Join Date: Sep 2008
Location: Harrison, Arkansas
Posts: 9,815
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Re: 72 C20 with an interesting previous owner NL2 aux tank modification
Jocko, I have been ordering my gas tanks from Autozone. it's the same tank, no shipping and easy return if it's damaged.
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other Larry Build thread, Arkansas K10 https://67-72chevytrucks.com/vboard/...=755797&page=5 The ability to speak several languages is an asset, but the ability to keep your mouth shut in any language is priceless. |
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#8 |
Senior Member
![]() Join Date: Oct 2009
Location: Godley, TX
Posts: 17,963
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Re: 72 C20 with an interesting previous owner NL2 aux tank modification
NOW ya tell me!
![]() Yeah, if I had it to do over…. I’m also pretty close to Summit HQ in N TX, coulda just driven over there to pick it up. Lesson learned, I’m gonna need another one for a different truck not too far off in the future. Thanks for the note, that’s a good tip. |
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#9 |
Active Member
![]() Join Date: Jun 2018
Location: Central Coast, CA
Posts: 126
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Re: 72 C20 with an interesting previous owner NL2 aux tank modification
My truck has dual saddle tanks and no in-cab tank. It had a double-pole, double-throw switch very much like that one, mounted under the gauge panel, and (still has) a selector valve like that.
The valve is available new from tanksinc.com. Don't know if it's based on a previous GM item. Figured my setup was just something a dealer or other outfitter installed. The wire gauge for the sender signals was like 14 awg -- way too much for just a signal.
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1971 Pontiac Firebird 1971 GMC C2500 |
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#10 |
Registered User
Join Date: May 2013
Location: Oregon
Posts: 327
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Re: 72 C20 with an interesting previous owner NL2 aux tank modification
That looks very much like my aftermarket tank switch and valve that was added in the 80s, except mine only has 3 hoses. The sender in my aux tank (left side, right behind cab) has shown over full every since I bought the truck in 2000. I rarely use it, so I havent bothered fixing it.
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#11 |
Senior Member
![]() Join Date: Oct 2009
Location: Godley, TX
Posts: 17,963
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Re: 72 C20 with an interesting previous owner NL2 aux tank modification
thanks very much sloGMC and CastIron! Yes, I'd agree, for the valve itself, 2 inlets and 1 outlet would seem more than sufficient! (or maybe 3 inlets to accommodate aftermarket dual saddle tanks).
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#12 |
All about them K’s
![]() Join Date: Jun 2014
Location: Land of Entrapment
Posts: 6,374
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Re: 72 C20 with an interesting previous owner NL2 aux tank modification
This is an Interesting thread. Thanks for sharing Mark. I think I may do something similar when I put my NL2 tank setup back in my K20. I’d never even thought about doing it this way.
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Tyler '57 3100 http://67-72chevytrucks.com/vboard/s...d.php?t=813888 '72 K20 Cheyenne http://67-72chevytrucks.com/vboard/s...d.php?t=662879 ‘69 K10 SWB http://67-72chevytrucks.com/vboard/s...d.php?t=805206 '98 Silverado LT K2500HD ECLB Vortec 454/4l80E: 6" lift 315/75/16's ‘87 IROC-Z all original 50K mile survivor TPI 305 IROC Blue ‘10 Camaro 2SS/RS Aqua Blue Metallic #93 -version 2.0 ![]() Last edited by 57taskforce; 07-16-2024 at 09:27 PM. |
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#13 |
Senior Member
![]() Join Date: Oct 2009
Location: Godley, TX
Posts: 17,963
|
Re: 72 C20 with an interesting previous owner NL2 aux tank modification
We're in the same boat Tyler - I agree, a good idea. One thing I noticed is that the tanksinc.com (thanks again sloGMC) only has a 5/16" line version (I gotta go check, I thought I had 3/8" lines for some reason - I think most of the rubber under the cab was labeled 3/8 fuel, but who knows how much of that is just po mods.. I just need to go take a closer look when I get a chance. Near term I'm just putting in a factory solid line from tank to pump until I get around to restoring the aux tank, I'll splice it to the valve later.
I'd be interested in seeing how an original (untouched) NL2 equipped truck's lines were routed - I've got a rat's nest of rubber lines that don't seem to be quite original for a factory setup. |
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#14 |
Senior Member
![]() Join Date: Feb 2022
Location: Ca
Posts: 498
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Re: 72 C20 with an interesting previous owner NL2 aux tank modification
If you need to switch return lines as well as feed, and control the gauge circuit, this will do all of it. You can add a second one and control 3 tanks all with the rotation of a single rotary switch and a bit of wiring knowledge. My setup works perfect. No floor lever and a factory looking knob. 3 port if no return line, 6 port if you use the return lines.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 |
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#15 |
Senior Member
![]() Join Date: Oct 2009
Location: Godley, TX
Posts: 17,963
|
Re: 72 C20 with an interesting previous owner NL2 aux tank modification
Thanks for the link PbFut!
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#16 |
All about them K’s
![]() Join Date: Jun 2014
Location: Land of Entrapment
Posts: 6,374
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Re: 72 C20 with an interesting previous owner NL2 aux tank modification
Awesome! I bookmarked that one!
__________________
Tyler '57 3100 http://67-72chevytrucks.com/vboard/s...d.php?t=813888 '72 K20 Cheyenne http://67-72chevytrucks.com/vboard/s...d.php?t=662879 ‘69 K10 SWB http://67-72chevytrucks.com/vboard/s...d.php?t=805206 '98 Silverado LT K2500HD ECLB Vortec 454/4l80E: 6" lift 315/75/16's ‘87 IROC-Z all original 50K mile survivor TPI 305 IROC Blue ‘10 Camaro 2SS/RS Aqua Blue Metallic #93 -version 2.0 ![]() |
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#17 |
Senior Member
![]() Join Date: Apr 2016
Location: Cypress, TX
Posts: 3,702
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Re: 72 C20 with an interesting previous owner NL2 aux tank modification
Can anybody explain how the electric valve works? Is it normally connecting the fuel pump line to tank 1 and when power gets applied to the valve (and stays applied) it connects the fuel pump to tank 2?
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#18 |
Senior Member
![]() Join Date: Oct 2009
Location: Godley, TX
Posts: 17,963
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Re: 72 C20 with an interesting previous owner NL2 aux tank modification
not to beat a dead horse but the replacement fuel tank arrived today and, although the filler neck was good to go, the other corner was damaged. Tank seam is intact, so I'll just hammer n dolly it and it will be fine - but still pretty annoying. I'll be following davischevy's advice next time.
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#19 | |
Senior Member
![]() Join Date: Aug 2013
Location: Northern Santa Barbara County, California
Posts: 2,680
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Re: 72 C20 with an interesting previous owner NL2 aux tank modification
Quote:
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aux tank, nl2 |
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