Simple Dual Fuel Tank Plumbing - Will this work?

[gringorick]

Been lurching forever. Thanks to everyone here for all the help over the many years. I am setting up my 1995 Toyota FZJ80 Land Cruiser for long-term expedition travel, and want to install a simple (i.e. inexpensive) dual/aux fuel tank. I cannot find any threads that discuss this setup, and am hoping to find someone who has done it, or who can tell me why I shouldn't do it.


I want to install a random fuel tank from another vehicle (15 gals or so) under the spare tire area. I will cut the fuel filler pipe an add a "tee" that will go the aux tank inlet. Both tanks will always fill at the same time. I will add a fuel pump (switched in the cab) to transfer fuel from the aux tank to the main tank when the main gets low. Fuel will be pumped into the main tank's vent line via another tee.


Seems easy enough, but I am sure there is something that I am missing.


Q1 - If I put the filler tee down at the lower end of the filler line, will it cause back turbulence and make the pump cutoff during filling?


Q2 - Will fuel transfer thru the vent line work?


Thanks for any help!

 

[Scoutn79]

Sounds like it would work just fine....Only thing is you need to remember to shut off the transfer pump and you won't know exactly when the "transfer" is complete. Maybe you could use the aux tanks fuel sender and wire in a gage or maybe a low pressure fuel gage might read line pressure during the transfer or a flow meter and you could see when the pump has moved all of the fuel.

Pretty simple idea and with a few tweaks it should work fine. The only possible issue is the filling of the aux tank after the main fills. Due to the design of the stock filler line the main will more than likely fill first then the fuel will flow into the aux tank once the fuel level is high enough. Make sure the filler and vent to the aux tank flow down hill or you will have issues.

Can't answer Q1 as each application is different. These pumps these days are set so light some won't even fill up my tank without me fighting it the entire time since it keeps shutting off and I haven't changed the set-up from stock.

Darrell

 

[swcruiser]

subtank

LCs in other markets received subtanks and some guys import them. Check on www.ih8mud.com and you will find a lot of installs for the OEM subtanks. I have one in fact. U can fill the tank from the other via the vent line but I don't think the idea of filling the tanks via a split main filler is a good idea. Its hard to control the amount going to each tank. The LCs with subtanks use a dual filler neck. When you pull a lever you close one filler to fill the other. These are frequently available on the site i mentioned or from the dealer. On the site you can also find a transfer switch that George S. made to shut off the tranfer pump. If you don't have a gauge i think you would need this to know when the subtank is empty. It takes a awhile and its easy to forget about.

 

[gringorick]

Thanks for the info! I am now working on 3 different possible scenarios - all include a transfer pump into the main tank. 1) OEM dual filler valve - most expensive and so far unavailable, 2) Separate filler for the aux tank - simple if I can find a good accessible spot for the filler - plus I only need to fill the aux tank when I want to, and 3) my original T idea - seems easiest and least expensive, but no control over which tank gets filled, so I will have to fill the full 40+ gallons every time, which is really not too big of a deal (less gas station trips) and only about 140 or so pounds extra when full.

My spare is relocated on back bumper, but I had someone install a hitch receiver in my Slee rear bumper and he welded a gigantic cross member tube form side to side, so I do not think the OEM subtank will fit... plus I do want about 20 gallons. I think I can find a tank to fit, it is the filler that is the hardest issue right now.

I am still looking for any reasons why the T method will not work as planned - it seems odd that no one has done this...

 

[Dan Grec]

I've spent some time thinking about this in the past.

I'm wondering about an even easier setup using a gravity feed. My idea would be to buy a second tank from some other vehicle that will fit. The benifit here is you get a roll over valve, etc.
Mount the second tank then connect the two tanks with a hose "at the bottom" for the gas to flow in/out, and a hose "at the top" for air to move in/out.
No secondary pump or transfer pump required here, it's a straight gravity feed.

I need to look into the legalities of this too.

-Dan

 

[Scoutn79]

I've spent some time thinking about this in the past.

I'm wondering about an even easier setup using a gravity feed. My idea would be to buy a second tank from some other vehicle that will fit. The benifit here is you get a roll over valve, etc.
Mount the second tank then connect the two tanks with a hose "at the bottom" for the gas to flow in/out, and a hose "at the top" for air to move in/out.
No secondary pump or transfer pump required here, it's a straight gravity feed.

I need to look into the legalities of this too.

-Dan

Some over the road trucks use this design to connect right and left tanks.
Darrell

 

[fabjunkie]

I set up a similar deal on my factory dual tanks as I was tired of fighting the switching valve and didn't want the un-reliability of it. I just set up a inline pump from the second tank and it feeds into a tee on the filler vent hose of the first tank. For the gauge, I wired in a SPDT switch so I can see how much either tank has on the one gauge.

 

[86tuning]

I'm wondering about an even easier setup using a gravity feed.

I need to look into the legalities of this too.

Problem is that its illegal due to fire hazard from possible leaks.

I'd recommend a transfer pump of some sort. Any small electric pump will work fine. If there's a leak, you can shut it off. With a gravity setup you'd never know there's a leak until you see a puddle on the ground....or a trail of gas behind your vehicle.

 

[bfdiesel]

Problem is that its illegal due to fire hazard from possible leaks.

I'd recommend a transfer pump of some sort. Any small electric pump will work fine. If there's a leak, you can shut it off. With a gravity setup you'd never know there's a leak until you see a puddle on the ground....or a trail of gas behind your vehicle.

How are you going to know there is a leak with the pump right away? Same way as the fuel tank tie a trail or the smell of gas. The saddle tanks on my subaru use an internal tie, not sure really how it works for self priming but might be worth researching as it would keep you from needing a hole in the bottom of the tanks. Having another pump is one more pump that can fail.

 

[Dan Grec]

Problem is that its illegal due to fire hazard from possible leaks.

Yeah, always having gas in the "lower" tube is far from ideal.

Another idea:

How about two tanks, and plumb a line from the regular pump pick-up over to the secondary tank, so there are two pick-ups on the one pump.
That line could exit tank 1 and enter tank 2 on top of the tanks, so it's not a "leak risk".

In that way, the pump would be sucking gas from either tank all the time.

Am I crazy?

-Dan

 

[Rattler_thesnake]

I'm interested in this too for my jk.. Genright is just too spendy$$$

 

[86tuning]

How are you going to know there is a leak with the pump right away? Same way as the fuel tank tie a trail or the smell of gas. The saddle tanks on my subaru use an internal tie, not sure really how it works for self priming but might be worth researching as it would keep you from needing a hole in the bottom of the tanks. Having another pump is one more pump that can fail.

Yeah but if you smell gas or see it drip on the ground you can shut it off. Also, you're in control of the fuel transfer; ie it doesn't happen without you turning it on.

Not the case with a gravity feed system and a leak. A fuel leak may empty BOTH of your tanks depending on how its set up.

The Toyota saddle tanks use a jet pump to move the fuel from one saddle to the other. The jet pump has no moving parts, it creates suction from a Venturi or 'jet' inside to draw the fuel over.

 

[peekay]

not sure if anyone's mentioned this, but here's my setup.

RDS 30 gallon aux tank in bed.
2007 Tacoma.
Holley Blue fuel pump.
1. Aux tank--->T fitting in stock inlet
2. Stock vent line on fuel neck---> back into Aux Tank
Aux tank vent line is t-ed into the stock charcoal canister
No. 2 is located slightly higher than No. 1. If the stock tank becomes full and you forget to turn off the pump, this allows the extra gas being pumped to recirculate back into the aux tank. And believe me, you will forget to turn that pump off! It takes probably 10 minutes to pump 15-20 gallons. Hard to tell bc the stock gauge has quite a bit of lag so it's difficult to tell that the tank is full until 5-7 minutes later.

This setup does result in some siphoning of the gas from the aux tank into the stock tank--resulting in the stock tank being continuously full for quite a while. It doesn't really hurt anything. I do throw off CE lights every 1000 miles or so. I have a Scangauge so I just instantly turn the light off. Haven't noticed any adverse effects.

Also, to specifically answer your questions:
1. I can still fill up normally--it does not trip the auto-fill on typical gas stations in CA, UT, AZ, and NV.
2. You can T into the ventline for your fill circuit--unless your transfer pump will be so fast that the ventline cannot accommodate the volume. But for the reasons set forth above, I highly recommend a return line to avoid overfilling.

 

[ssapach]

For what it's worth, I've had an electric transfer on my 2006 Sierra for nearly 7 years. I had it installed in July of 2006 actually.

Quite simply, I have a fuel tank in the box of the truck and have an electric pump and valve hooked up. It's simply split into the vent line from the main fuel tank and I can only fill my auxiliary tank from it's own filler.

I don't have a fuel gauge on my aux tank and if I'm transferring to my truck tank while driving, the truck's fuel gauge won't read accurately and the tank is actually full when the gauge shows about 3/4. It's not a big deal if you pay attention when filling, but the first time was the learning experience when I realized there was diesel coming out of the truck's fuel cap.

So far it's still working like it did when it was new. I do have a feeling I might need to get the pump and valve replaced before they become problematic as the rust has taken a bit of a toll on them.

 

[magentawave]

gringorick - Did you ever do this? If so, how did it work for you? I as thinking of just adding another tank and with a pipe between each of them so as to avoid another fuel filler neck and extra pump, etc. I don't know how to connect the two tanks so they won't leak though.