Auxiliary tank.....can I do this

[gregg72340]

I am buying some parts of a guy local and he is parting out a 72 long bed with an auxiliary tank. It is all there, is it feasible that I could use the Aux tank set up as my main gas tank to get it out of the cab and does anyone know how many gallons they are?

Thanks

[Reed's72]

I was thinking about doing the same thing, my gmc had 2 aux tanks that I was told were 14 gal each. When I pulled them off it looked like they had the same sending units as the main

[chevy_mike]

I did that on my 1st '68. It had dual aux tanks and the in cab one. I removed the in cab and put an electronic valve to switch between tanks. Since both aux tanks had senders, I wired things so when I switched the valve, it also switched the sender input. Worked great. I think my tanks were like 16-18 gallon but it was 10+ years ago so I don't remember.

[gregg72340]

So it seriously is a bolt in deal????

[72freak]

When I bought mine it was running on the aux. tank only. The main tank was not even plumbed......you just wont have a sending unit. Now....pull out the aux. tank, find the depth of it and get a correct OHM adjustable sending unit or one for a blazer tank, fill the tank with water, drill a hole, let the tank dry install and wire sending unit, fill it back up with gas and you should be good to go.

[gregg72340]

Ok guess my question here is one guy says the have a sender and the other syas they dont, so which one is correct? if I do this I would like it to be a strictly bolt in deal sender and all, just run a new wire from the old sender to the new one and strap it in and have it be the main tank.

[chevy_mike]

It can be either. Depends on who/where the tanks came from. My 1st '68 had senders in both. My current '68 did not have one in the single aux. You will have to check out the tank to see.

[gregg72340]

Originally Posted by chevy_mike

It can be either. Depends on who/where the tanks came from. My 1st '68 had senders in both. My current '68 did not have one in the single aux. You will have to check out the tank to see.

Ok now Im on the same page with you, I was confused, ok well hopefully when I go look at it I can tell, Thanks for the info about that
Greatly appreciated because I havent looked all that closely at this and the truck is in a field with lots of bees,(What is the deal with these trucks and all the bees?!?!?!) and it was more of an after thought after I went and looked at it yesterday and actually have never seen one of these set ups before so wasnt sure what it actually was or if I could use it

[BobS]

gregg72340,

If it's the factory RPO (NL2? - check the glove box door), it will have a sender in the tank, a valve on the floor of the cab with a plastic tag indicating main or aux tank, and a switch to the left of the instrument panel with a knob like the other knobs on the dash with a label above it indicating main or aux tank. The filler neck will be through the side of the box and the piping to the tank will be covered by the same cover as used on Jimmys and Blazers. The sender in the aux tank is shorter than a Jimmy/Blazer pickup because the tank isn't as deep. You could use just the auxiliary tank but the capacity is less than the main tank, IIRC it holds 14-15 gallons.

Bob

[mrein3]

When I got my truck it had one of these auxiliary tanks installed. No sender. I asked the PO how he knew how much gas was in there. He said simple. You fill it to the top. Run off that tank until the truck starts to buck, then switch over to the seat tank. Then you know you either have some or none.

He also knew it leaked.

I dropped the tank, had it repaired, and ordered a generic fuel sender/gauge from JC Whitney.

When I got the repaired tank back, like 72freak says, I filled it water and drilled a hole for the sender.

The gauge I mounted knee-knocker style below the ignition.

Regarding the amount of gas it holds, I have run it dry and have never got more than 17 gallons in it.

I don't see any reason why you couldn't use it as a primary tank other than the reduced capacity.

[72 cheyenne pdx]

I run only my aux tanks. I have the original 3-way toggle switch in the dash and a mechanical valve on the floor between the door and seat. Mine holds a total of 34 gallons (17 in ea.). If your truck already had Aux tank(s) before and replacing it, it should be a bolt in type of deal. If you are adding an Aux tank, you will have to plumb hose(s), the neck, run the sender wire, cut out the hole in the bed or bedside(s), and possily drill the holes in the frame to mount the tank. It may be better just to add the blazer tank between the frame rails.

Good luck