Insane fuel tank thought!!

[EagleChief]

So, a little background on why this thought came to me - I'm adding a fuel tank under the bed for my LS swap. I still have the stock tank behind the seat. The plan is to remove it. But, my project is going on year 4-ish.

Here's my thought/question/discussion while laying in bed awake in the middle of the night, or when I wake up in the middle of the night and can't go back to sleep:

I wonder if I can leave the original tank behind the seat and re-plumb it to feed into the tank under the bed. Would it be possible to have the stock fuel tank as an extra supply on top of my fuel tank that is going under the bed? I know it would need a valve of some sort to restrict the flow into the lower tank. Gravity feed wouldn't have a way to shut off, as the tank is higher and would continuously feed the lower tank. Could I run a pump from the original to feed the other and then the main pump to go from there to the engine?

I know it's a dumb idea, but like I said. Sometimes I can't sleep and this is something that I pondered while laying in bed one night.

[72c20customcamper]

Just use a switch to go from one to the other . I used one in my 68 for the keg gas tank I have 13 more gallons now

[jaros44sr]

These trucks did come with brass vavle for extra tanks, you could mount the vavle in the stock location

20191005_074950 by [url=https://www.flickr.com/photos/97391199@N06

[57taskforce]

You would have to have a pump for sure, because the lines don’t gravity feed on the stock sending unit/tank setup. I don’t think it’s a dumb idea. I’ve thought about doing similar for my factory auxiliary tank setup so you don’t have to mess with the brass valve when the first tank runs out. As you see it running low you hit the pump in the cab tank and have it fill the under bed tank. The sending unit switch from a factory aux tank truck would be perfect to be able to see what both tanks have in them.

[kwmech]

Did something similar with my flatbed. I have an auxiliary fuel tank under the bed behind the cab. Goes from cross member to cross member and only about 9 inches deep. Holds about 45-50 gallons. I used the newer style switching valve so I can switch the senders also

[weq92f]

.

My DD has a 30 gallon tank in the bed (disguised as a tool box that sits below the bed cover level).

It has a sending unit and pump in the AUX tank and is plumbed into the factory fuel tank via the filler neck. Inside the cab I've got a toggle switch for the AUX pump and a fuel gauge for the AUX tank. Main tank gets low, just hit the switch and put more fuel in there...right?

This works as you would expect however there are some issues:

The pump runs until it is toggled back off again. If the AUX tank goes empty, pump keeps running. If the target tank becomes full and the AUX tank still has fuel, the pump keeps running eventually dumping fuel to the atmosphere via the vent and stalling the engine (due to some fuel vapor catch that gets fouled by raw fuel when this happens). Once stalled, it takes a bit to get the engine running again.

Not perfect but is workable. I've determined that running the pump for 10 minutes equates to close to 8 gallons and am considering a timer to guard against wasting fuel. When I use the thing currently, I manually time the event with my pocket computer and run it only 10 mins at a time.

YMMV,

-Kevin

[PbFut]

Lots of things to consider here. First you are feeding a LS. Are you going carburation or fuel injected? Are you running return lines? Do you want intank pumps or inline pump. Are there sender units for gauge in each tank? The easiest way to plumb is with one inline pump and a selector valve. If you run a return line, it only adds the complication of switching its flow in sync with the feed flow. This is my device of choice. One valve for 2 tanks and it switches feed, return and sender signals. Works great. I have 3 tanks, so I need 2 valves. First valve selects main tank second valve. The second valve selects the 2 aux tanks. With the use of a 3 position rotary switch, it will switch the feed and return fuel lines and the sender signal so all circuits are sync’d at all times. No manual switching of a line valve and no out of sync toggle switch for the fuel gauge. This kit get you the pigtail. The valve does not require momentary switch. The switch can remain closed and not hurt the valve.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[EagleChief]

Originally Posted by PbFut

Lots of things to consider here. First you are feeding a LS. Are you going carburation or fuel injected? Are you running return lines? Do you want intank pumps or inline pump. Are there sender units for gauge in each tank? The easiest way to plumb is with one inline pump and a selector valve. If you run a return line, it only adds the complication of switching its flow in sync with the feed flow. This is my device of choice. One valve for 2 tanks and it switches feed, return and sender signals. Works great. I have 3 tanks, so I need 2 valves. First valve selects main tank second valve. The second valve selects the 2 aux tanks. With the use of a 3 position rotary switch, it will switch the feed and return fuel lines and the sender signal so all circuits are sync’d at all times. No manual switching of a line valve and no out of sync toggle switch for the fuel gauge. This kit get you the pigtail. The valve does not require momentary switch. The switch can remain closed and not hurt the valve.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

It is an FI setup. The tank under the bed is set up for FI with a sump and an in-tank fuel pump.

My original tank has an added fuel pump, in-line, under the cab. I could probably use it to fill the new tank, right? By using a switch to turn it on/off?

[57taskforce]

Originally Posted by EagleChief

It is an FI setup. The tank under the bed is set up for FI with a sump and an in-tank fuel pump.

My original tank has an added fuel pump, in-line, under the cab. I could probably use it to fill the new tank, right? By using a switch to turn it on/off?

Yes that would work.

[EagleChief]

Well, it's good to know that I wasn't going crazy!

I already have an external fuel pump that was installed by the previous owner. Actually had 2 of them for some unknown reason (never did figure that one out). I could use the one under the truck (mounted to the frame) to pull fuel from the stock tank, and send it to the rear tank. Sounds like the best solution would be to hook up an on/off switch for that pump. Run it for 'x' amount of time to dump fuel into my new tank, and just remember to shut it off.

This would allow me to keep the original fuel filler and not have to cut a new filler in the bed somewhere for the new tank. Not sure how big of a deal that is, but without having a lot of fab experience, it's one less thing to worry about.

[PbFut]

Running a line from one tank to the other is asking for problems with over filling the receiving tank. Normally you use one inline pump downstream from the valve. Pressure regulate the pumped fuel with return back to valve so it syncs into correct tank. Feed your fi system from the regulator.