72 C20 with an interesting previous owner NL2 aux tank modification

[jocko]

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 Still a pain to have to drag the old (new) damaged one back to FedEx, but that's the way the tank bounces sometimes .

[jerry moss]

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.

[jocko]

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).

[jerry moss]

Originally Posted by jocko

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).

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.

[dmack91]

It looks like the factory squarebody switching valve from a mid to late 70s square.

[jocko]

Thanks guys!

[davischevy]

Jocko, I have been ordering my gas tanks from Autozone. it's the same tank, no shipping and easy return if it's damaged.

[jocko]

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.

[sloGMC]

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.

[CastIron]

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.

[jocko]

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).

[57taskforce]

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.

[jocko]

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.

[PbFut]

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

[jocko]

Thanks for the link PbFut!

[57taskforce]

Awesome! I bookmarked that one!

[dmjlambert]

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?

[jocko]

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.

[Cali72K20]

Originally Posted by jocko

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 Still a pain to have to drag the old (new) damaged one back to FedEx, but that's the way the tank bounces sometimes .

My C20 had the same style switch installed but it looked hacked in. I googled the part number and comes up as an Eaton MIL spec.