Aux fuel tank info

[Cali72K20]

Hello All!

I was going to start on the aux fuel tank by cleaning and painting it but, the PO had removed it with all the lines and wiring. my delima is there any info on how these go back together and I also need to rebuild the transfer switch next to the driver seat on the floorboard. Any info will be greatly appreciated!!
I did use the search engine but I had no luck.
I believe it is the factory installed tank.

Casey

[DeadheadNM]

Here are some pics I've collected here on the board:

[jocko]

this might help for dual aux tanks

[SS Tim]

Its easy enough. First thing I recommend is everyone have a set of factory manuals. There are online copies you can download that are workable interim (see my signature).
Since you didn't give much information are we to correctly assume you are asking about the factory NL2 left side tank and it is listed on your SPID?

If it was added or a dealer installed there may be differences.

In operation it (NL2) is a manualy selected tank via a floor mounted valve and lever handel. It also has a fuel gauge selector switch on the far left dash, left of the cluster. This only switches the gauge not the fuel.

Most of the information you would like to see is in the "assembly manual". This is more or less a collection of assembly oppperations concentrating on options installation. There is a lot of good information but its not paginated nor indexed. There is an index here on the board assembled by members but I haven't used it.

Here are a few pictures to get you started.
The fuel lines snake back and forth under the cab from the hardline to the tank and the selector. Don't have a diagram on hand at the moment, sorry.

[DeadheadNM]

More - the dash decal is now reproduced by a board member....

[jocko]

here's what else I have (I think one is a dupe of pete's)

[SS Tim]

Well that was interesting... might as well just go shovel some more used dog food! :-)

[swamp rat]

Subscribed for (maybe) future reference..

[FirstOwner69]

Originally Posted by SS Tim

Well that was interesting... might as well just go shovel some more used dog food! :-)

Now THAT is the funniest thing I've read on this forum!!!

[Cali72K20]

Thanks Everyone!!!!!
It is the NL2 version, everything is there but the hoses. The floorboard switch looks cruddy and the tank needs to be cleaned and painted. It has all the wiring to it but its not hooked up. Thanks again for all the info!

casey

[Haggis]

Interesting... I have the dual aux tank option, but do not have the switch to change the gauge over. I will have to see if any of this wiring is there and make it functional again.

[SS Tim]

Originally Posted by Haggis

Interesting... I have the dual aux tank option, but do not have the switch to change the gauge over. I will have to see if any of this wiring is there and make it functional again.

Unless you have the factory optional tank NL2 or the earlier N18 tank it is probably an aftermarket tank and does not have a gauge provision. A true factory aux tank will be on the SPID.

Most of the in-bed or underbed dual or saddle tanks were aftermarket not GM accesssories.

They can have bedside doors added, through bed filler pipes or wheel well fillers. Anyone could have installed them including a dealer, RV retailer or even the owner.

While it is possible to find the GM accessory tanks. These were offered as a single, a single supplememt to the NL2 (making them saddle tanks) or even a full gauged saddle tank set. They are very rarely seen. These are illustrated in the tan installation drawings Jocko posted.

[special-K]

Hey Cali72K20,does the truck still have the splash guard that protects the valve? I have that and a valve from a Cali72K20() I no longer have,if needed

All the dual tanks are aftermarket and they offered a 3-position gauge switch (left/main/right). I guess some never got those installed,but most I've had or seen had the (toggle) switch.

[Haggis]

Sounds like mine are aftermarket then. No switch or wiring and its not on my SPID. No big deal, at least they are functional.

[special-K]

That's what my '72 has. They were a common upgrade that GM woke up and started offering. By '73 we saw a dual tanks as a common option that was built-in as opposed to the after-thought design of the N18 and NL2. There is nothing inferior about the aftermarket tanks compared to factory

[DeadheadNM]

As an aside, did GM offer aux gas tanks as a factory option prior to 1970? When did Ford offer aux gas tanks?

[AASmedic]

Saving this one for later too. Just the info I was looking for.

[Woofwagon]

Subscribed. I purchased a '72 C20 that has the filler neck in the bed but no tank. I'd like to have the extra tank in there.

[57taskforce]

Subd... I’m gonna put my nl2 setup back together sooner or later.

[pilotXC]

Great info... Does anyone know what the bolts are called that hold these dealer installed tanks to the bed? Mine have the bolts through the middle of the tank with nuts welded to the flat end that threads into the long "carriage" bolt type that goes through the bed (not sure what else to call them besides carriage bolts). 3 of the 4 nuts broke off when I tried to take them off, they were just spot welded in 2 places, so need to try to weld them back on and break them loose, but would love to replace them with new bolts and can't figure out what they are called or who might sell them.

[Steeveedee]

I used threaded rod with locking nuts when I put mine in after dropping them to get all the bad gas out of them.