What’s this for - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Captain J · 06-11-2020, 09:33 AM

Can someone tell me what this knob for?
1972 GMC Sierra
Truck have only one in cab fuel tank

**68bowtie** · 06-11-2020, 09:36 AM

I bet it’s anti-theft

Captain J · 06-12-2020, 07:22 AM

Quote:

Originally Posted by 68bowtie

I bet it’s anti-theft

🤣🤣🤪🤪🤪
It might be.

**DeadheadNM** · 06-11-2020, 09:36 AM

It's a switch to toggle between the sending units for the in-cab fuel tank and the now missing but once present auxiliary fuel tank.

Post up a photo of the build decal (SPID) on the glove box door if present

Killer Bee · 06-12-2020, 06:34 AM

to add to that, if you follow the fuel supply line from the tank underneath the cab and you might find evidence of it's removal..

Captain J · 06-12-2020, 07:24 AM

Quote:

Originally Posted by Killer Bee

to add to that, if you follow the fuel supply line from the tank underneath the cab and you might find evidence of it's removal..

I’ll check,

Captain J · 06-12-2020, 07:23 AM

Quote:

Originally Posted by DeadheadNM

It's a switch to toggle between the sending units for the in-cab fuel tank and the now missing but once present auxiliary fuel tank.
Not sure,
Post up a photo of the build decal (SPID) on the glove box door if present

I’ll thanks

Captain J · 06-14-2020, 05:06 AM

Quote:

Originally Posted by DeadheadNM

It's a switch to toggle between the sending units for the in-cab fuel tank and the now missing but once present auxiliary fuel tank.

Post up a photo of the build decal (SPID) on the glove box door if present

Decal says it has an aux fuel tank, surprise surprise,
🧐

**special-K** · 06-12-2020, 07:00 AM

That's the '72 auxiliary fuel tank gauge switch to read levels in both tanks. There should be a hole in the floor between driver seat and door where the control valve was mounted. Might even still have the valve and placard in place. I guess someone removed the tank. Might have filled the filler hole in the upper forward part of the bedside or switched beds

Captain J · 06-12-2020, 07:27 AM

Quote:

Originally Posted by special-K

That's the '72 auxiliary fuel tank gauge switch to read levels in both tanks. There should be a hole in the floor between driver seat and door where the control valve was mounted. Might even still have the valve and placard in place. I guess someone removed the tank. Might have filled the filler hole in the upper forward part of the bedside or switched beds

But where was the aux fuel tank located?
As I saw no evidence of aux fuel tank, but I’ll look for the valve and placard.
Thanks

**MJN** · 06-12-2020, 11:57 AM

Quote:

Originally Posted by Captain J

But where was the aux fuel tank located?
As I saw no evidence of aux fuel tank, but I’ll look for the valve and placard.
Thanks

Aux fuel tanks were under the box, between the bedside and the frame rail. If there is no filler hole in either bed side I have seen aux fuel tanks that had fill necks inside the rear wheel housing in front of the rear wheel.

**special-K** · 06-12-2020, 10:56 PM

Quote:

Originally Posted by Captain J

But where was the aux fuel tank located?
As I saw no evidence of aux fuel tank, but I’ll look for the valve and placard.
Thanks

Driver side front between bedside and chassis. The other thing, if it still has the same bed, would be the filler tube cover. About 3"-4" wide square "duct" from top of bedside to floor that covered the fuel fill tube.

**jocko** · 06-12-2020, 12:18 PM

NL2 RPO was what got you a single, driver's side only aux fuel tank setup, which included the fuel gauge selector in your picture and a left (only) bedside fuel filler - i.e. a fuel cap just like the cab tank cap, but located on the bed, as shown below. The fuel flow selection valve was on the driver's side floor just inside the door sill and in front of the seat belt retractor. No passenger side fuel fills were available from the factory nor were wheelwell fill tanks - but there were several different vendors that offered dual saddle tank installs - but they would not have had the switch shown in post 1 though. Dealers could also install saddle tanks - but these setups only had the cuts in the bedside for the little metal, lockable fuel filler access doors or wheelwell filler necks. Do you have NL2 on your SPID? If no filler neck on bed, then it's been filled or bed is not original to the truck (assuming NL2 is on your SPID).

Captain J · 06-14-2020, 05:11 AM

Quote:

Originally Posted by jocko

NL2 RPO was what got you a single, driver's side only aux fuel tank setup, which included the fuel gauge selector in your picture and a left (only) bedside fuel filler - i.e. a fuel cap just like the cab tank cap, but located on the bed, as shown below. The fuel flow selection valve was on the driver's side floor just inside the door sill and in front of the seat belt retractor. No passenger side fuel fills were available from the factory nor were wheelwell fill tanks - but there were several different vendors that offered dual saddle tank installs - but they would not have had the switch shown in post 1 though. Dealers could also install saddle tanks - but these setups only had the cuts in the bedside for the little metal, lockable fuel filler access doors or wheelwell filler necks. Do you have NL2 on your SPID? If no filler neck on bed, then it's been filled or bed is not original to the truck (assuming NL2 is on your SPID).

Couldn’t find either of them, must remove all.

But where is the location of the aux tank and how it’s connected, size of the tank. I like to re install it if easy.

**special-K** · 06-14-2020, 08:38 AM

Quote:

Originally Posted by special-K

Driver side front between bedside and chassis. The other thing, if it still has the same bed, would be the filler tube cover. About 3"-4" wide square "duct" from top of bedside to floor that covered the fuel fill tube.

Quote:

Originally Posted by Captain J

Couldn’t find either of them, must remove all.

But where is the location of the aux tank and how it’s connected, size of the tank. I like to re install it if easy.

I answered a couple of those questions. The fuel line runs from top of tank to the valve in the floor and from valve to fuel pump. The valve is body is a "block", I would call it, like the t-block in your rear brake lines. You'd have to ask for pictures for proper routing.

The tank is something like 10-12 gallons if I remember correctly.

There is also a piece I'd call a guard that mounts across the front of the valve to protect it.

Captain J · 06-14-2020, 01:05 PM

Quote:

Originally Posted by special-K

I answered a couple of those questions. The fuel line runs from top of tank to the valve in the floor and from valve to fuel pump. The valve is body is a "block", I would call it, like the t-block in your rear brake lines. You'd have to ask for pictures for proper routing.

The tank is something like 10-12 gallons if I remember correctly.

There is also a piece I'd call a guard that mounts across the front of the valve to protect it.

Thanks, I found the fuel filler capped (on the left side) painted over, the valve is removed, no fuel lines.
Again thanks for your help 👋🏻

Captain J · 06-14-2020, 05:13 AM

Quote:

Originally Posted by jocko

NL2 RPO was what got you a single, driver's side only aux fuel tank setup, which included the fuel gauge selector in your picture and a left (only) bedside fuel filler - i.e. a fuel cap just like the cab tank cap, but located on the bed, as shown below. The fuel flow selection valve was on the driver's side floor just inside the door sill and in front of the seat belt retractor. No passenger side fuel fills were available from the factory nor were wheelwell fill tanks - but there were several different vendors that offered dual saddle tank installs - but they would not have had the switch shown in post 1 though. Dealers could also install saddle tanks - but these setups only had the cuts in the bedside for the little metal, lockable fuel filler access doors or wheelwell filler necks. Do you have NL2 on your SPID? If no filler neck on bed, then it's been filled or bed is not original to the truck (assuming NL2 is on your SPID).

I’m not familiar with NL2 & SPID!

sick472 · 06-14-2020, 07:24 AM

SPID = service parts identification... It's the sticker that was put on the inside of the glovebox door that has the options that where ordered with the truck. NL2 was the aux tank option code.

Captain J · 06-14-2020, 07:32 AM

Quote:

Originally Posted by sick472

SPID = service parts identification... It's the sticker that was put on the inside of the glovebox door that has the options that where ordered with the truck. NL2 was the aux tank option code.

It has that code NL2, but none exist

57taskforce · 06-14-2020, 06:04 PM

Here’s the NL2 tank and filler from my K20.

Cesar Diaz · 07-01-2020, 11:15 AM

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Captain J · 07-01-2020, 11:23 AM

I wish I can, I’m 3500miles away, cost of shipping exceeds the value of the switch.

doowopper · 11-11-2020, 04:02 AM

Are replacement SPIDs available?

Thanks,
Roger

**LockDoc** · 11-11-2020, 11:07 AM

Quote:

Originally Posted by doowopper

Are replacement SPIDs available?

Thanks,
Roger

Yes they are.

http://outintheshop.com/

A lot of other good info on there also.

Jeff is a member on here and a really nice guy.

LockDoc

doowopper · 11-11-2020, 02:25 PM

Quote:

Originally Posted by LockDoc

Yes they are.

http://outintheshop.com/

A lot of other good info on there also.

Jeff is a member on here and a really nice guy.

LockDoc

Doc, thanks a million. That site is a keeper.

Roger

06-11-2020, 09:33 AM	#1
Captain J Registered User Join Date: Nov 2017 Location: H, Q Posts: 180	What’s this for Can someone tell me what this knob for? 1972 GMC Sierra Truck have only one in cab fuel tank Attached Images __________________ 1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454

06-11-2020, 09:36 AM	#2
68bowtie Senior Member Join Date: Jan 2007 Location: Turlock, CA Posts: 8,795	Re: What’s this for I bet it’s anti-theft __________________ Please help my sister in law with her battle with cancer https://gofund.me/902f6fce Project "C10 Fever" (68 factory black 396 swb) Project "Little Sister" (70 c10 blue original paint refresh) Project "Blue Bomb" (70 c30 blue original paint refresh) SOLD Project "Vitamin C" (71 c10 orange original paint refresh) SOLD

06-11-2020, 09:36 AM	#4
DeadheadNM Carpe manana Join Date: Dec 2010 Location: Eau Claire, WI Posts: 12,443	Re: What’s this for It's a switch to toggle between the sending units for the in-cab fuel tank and the now missing but once present auxiliary fuel tank. Post up a photo of the build decal (SPID) on the glove box door if present __________________ 1972 K5 CST Highlander Blazer: http://67-72chevytrucks.com/vboard/s...d.php?t=708547 1972 K20 Cheyenne Super: http://67-72chevytrucks.com/vboard/s...d.php?t=528308 Members met: ORANGBLAZ, 2003 silverado, MikeCofield, BB72CHEVKT, Duncan&Son, Sameyrasmea72, THENEWMEXICAN, HotRod C/10, brianthelion02, Sport/Truck, ryanroo, michael bustamante, Dirt's72, Already Gone, WestButteTruck, 57taskforce, Moreyel, painterljp, AASmedic, SoCoC10, Lumaestas, carbuff382, Chevyland Last edited by DeadheadNM; 06-11-2020 at 09:37 AM. Reason: added

06-12-2020, 06:34 AM	#5
Killer Bee Registered User Join Date: Jan 2016 Location: Barber City, CA Posts: 4,809	Re: What’s this for to add to that, if you follow the fuel supply line from the tank underneath the cab and you might find evidence of it's removal.. __________________ *I started out with nothing - and I still have most of it*

06-12-2020, 07:00 AM	#9
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,851	Re: What’s this for That's the '72 auxiliary fuel tank gauge switch to read levels in both tanks. There should be a hole in the floor between driver seat and door where the control valve was mounted. Might even still have the valve and placard in place. I guess someone removed the tank. Might have filled the filler hole in the upper forward part of the bedside or switched beds __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

06-12-2020, 12:18 PM	#13
jocko Senior Member Join Date: Oct 2009 Location: Godley, TX Posts: 17,975	Re: What’s this for NL2 RPO was what got you a single, driver's side only aux fuel tank setup, which included the fuel gauge selector in your picture and a left (only) bedside fuel filler - i.e. a fuel cap just like the cab tank cap, but located on the bed, as shown below. The fuel flow selection valve was on the driver's side floor just inside the door sill and in front of the seat belt retractor. No passenger side fuel fills were available from the factory nor were wheelwell fill tanks - but there were several different vendors that offered dual saddle tank installs - but they would not have had the switch shown in post 1 though. Dealers could also install saddle tanks - but these setups only had the cuts in the bedside for the little metal, lockable fuel filler access doors or wheelwell filler necks. Do you have NL2 on your SPID? If no filler neck on bed, then it's been filled or bed is not original to the truck (assuming NL2 is on your SPID). Attached Images Last edited by jocko; 06-12-2020 at 12:24 PM.

06-14-2020, 07:24 AM	#18
sick472 Registered User Join Date: Jul 2015 Location: Sedalia Mo. Posts: 1,131	Re: What’s this for SPID = service parts identification... It's the sticker that was put on the inside of the glovebox door that has the options that where ordered with the truck. NL2 was the aux tank option code. __________________ He who is without oil shall throw the first rod. Compressions 8.7:1 1972 C10 1976 C10 (parts truck) 1985 K20

06-14-2020, 06:04 PM	#20
57taskforce All about them K’s Join Date: Jun 2014 Location: Land of Entrapment Posts: 6,487	Re: What’s this for Here’s the NL2 tank and filler from my K20. Attached Images __________________ Tyler '57 3100 http://67-72chevytrucks.com/vboard/s...d.php?t=813888 '72 K20 Cheyenne: 5” lift, 35’s, front dana 60 blah blah blah… http://67-72chevytrucks.com/vboard/s...d.php?t=662879 ‘69 K10 SWB: 4” lift 33”s… in a million pieces http://67-72chevytrucks.com/vboard/s...d.php?t=805206 '98 Silverado LT K2500HD ECLB Vortec 454/4l80E: 6" lift 35x12.5x20’s

07-01-2020, 11:15 AM	#21
Cesar Diaz Registered User Join Date: Jun 2016 Location: Stevenson Ranch, CA Posts: 62	Re: What’s this for Please note that you must be a supporting member to post classified items. This includes but is not limited to What Its Worth, Want To Buy, Want To Trade, and For Sale. Please consider supporting the forum by subscribing. Further information on the subscription levels available are located here If you need any further assistance with that please contact any Admin for help. __________________ Cesar Diaz 1972 C10 Big Block 402 Cheyenne Last edited by LockDoc; 07-01-2020 at 02:47 PM. Reason: WTB by Non-Premium member

07-01-2020, 11:23 AM	#22
Captain J Registered User Join Date: Nov 2017 Location: H, Q Posts: 180	Re: What’s this for I wish I can, I’m 3500miles away, cost of shipping exceeds the value of the switch. __________________ 1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454 Last edited by LockDoc; 07-01-2020 at 02:48 PM.

11-11-2020, 04:02 AM	#23
doowopper Registered User Join Date: Nov 2020 Location: socal Posts: 62	Re: What’s this for Are replacement SPIDs available? Thanks, Roger



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