Secondary Fuel Tank

[joshs1ofakindxj]

I'm installing a secondary stock fuel tank on the driver side where the spare tire was. I picked up a complete tank with sending unit and pump.

I did some research and I read it is a pain to plumb the tanks to the same line, and it is easier to pump fuel from the secondary into the main tank with a switch to power up the aux fuel tank pump.

I'm not interested in keeping the fuels separate.

I'm pretty sure I can wire an ON-OFF-ON switch to be able to check the level in either tank using the leads from the sending units to the two ON tabs.

Right now I'm just thinking about the plumbing.

Can I use normal fuel injection hose? I could run pipe but it would be simpler to just use barb fittings and run hose.

When I look at the tank, I see a plumbing location on the top that appears to be unused and I'm wondering if I can connect the line from the axillary pump to that connection on the main tank to dump fuel in. My one tank appears to have a plugged 90 deg elbow in the location and my other tank appears to have a small valve, like an air tank valve that is closed.

I'm looking for a picture to show what I mean...

Also, which TM has the information on setting the fuel pump height?

Thanks guys!

 

[hoop]

Yes you can use the elbow fitting and barbed fittings work, but copper flared would be better.
The pump should "not" be able to touch the bottom of the tank.

 

[gimpyrobb]

The in tank pump puts out 5-7 psi, regular hose will be fine, no need for fuel injection hose. I would also run the vent line to the primary tank too.

 

[joshs1ofakindxj]

The in tank pump puts out 5-7 psi, regular hose will be fine, no need for fuel injection hose. I would also run the vent line to the primary tank too.

Good call on the vent line. I believe it just uses 3/16" brake line?

 

[gimpyrobb]

Dunno off hand, sorry. I do believe rubber tube could be used there too.

 

[joshs1ofakindxj]

True.

 

[73m819]

For the correct dash switch and switch plate, get a gage slection switch for a m52a2, m51a1, or a m543a2, this switch is a DPDT

not sure if the 809 and the 900 5ts duel tank trucks are the same, but would guess yes

 

[simp5782]

Or look at one of these.

Eco-friendly 3-Way Manual Valve: Living ECHO

They also have some 4ways with long handles. OR you can look for a fuel selector valve off a ford truck 84-97 for around $40 new but $10 for the tank selector switch. Rockauto makes one that will work on a 24v system.

 

[joshs1ofakindxj]

Thanks guys, but I'll be doing this simple and cheap so I can get the truck ready for some trips.

Quick question: If I'm going to use an inline fuse meant for 12 volt, can I simply assume the rated amperage of the fuse to be "halved" or "doubled"? I was trying to figure it out from V=IR but I'm not making sense of it.

 

[gimpyrobb]

Your putting a fuse where? For what reason? The second tank should have a fused pump in it. No reason to add another fuse imho.

 

[joshs1ofakindxj]

When I take power from the batteries, I like to put a fuse within the first few inches of wire, that way if the wire somehow gets pinched or rubbed through somewhere in route to the dash switch and then the pump, it won't weld itself to something and kill my batteries.

Just a little extra protection.

I also need to run power to my reverse lights.

 

[gimpyrobb]

Ah, I would have used a "Y" military harnes. I would put a 20a fuse in to protect everything.

 

[quickfarms]

subscribed

 

[RedbeardTheZombieHunter]

I've thought about doing this too, but my hook up idea was a little different. My plan was to install the second tank on the driver's side where the spare was, but hook the two lines to a "T" fitting with check valves on each side. Then using an 8-post toggle switch, isolate the fuel pump power and gauge sender between right and left tanks. When the right tank is on, the right pump runs with the left check valve closed. When the left tank is powered, the right check valve closes and the gauge reads the left tank. Has anyone tried this and did it work well without problems. I almost forgot, I'll also use an electric tank switching solenoid to route the return lead from the IP. Can anyone think of why this wouldn't work?

 

[joshs1ofakindxj]

^That is along the lines of what I was thinking about doing originally, and has been done, but when I started pricing parts and thinking about it, I'm just going to keep it simple.

If I was running two different fuels and needed the separate plumbing then I would go that way but I run the same fuel all the time.

 

[RedbeardTheZombieHunter]

OK Cool. I can't fault anyone for observing the "KISS" principal.

 

[plym49]

Amps are amps, the voltage across an unblown fuse is zero, so a ten amp fuse is a ten amp fuse is a ten amp fuse on 24v, 12v or 6v. The only time voltage rating comes into play is if the voltage is high enough to overcome the fuse housings dielectric rating. Since you are probably not installing a 30,000 volt alternator, not to worry.

 

[plym49]

I've thought about doing this too, but my hook up idea was a little different. My plan was to install the second tank on the driver's side where the spare was, but hook the two lines to a "T" fitting with check valves on each side. Then using an 8-post toggle switch, isolate the fuel pump power and gauge sender between right and left tanks. When the right tank is on, the right pump runs with the left check valve closed. When the left tank is powered, the right check valve closes and the gauge reads the left tank. Has anyone tried this and did it work well without problems. I almost forgot, I'll also use an electric tank switching solenoid to route the return lead from the IP. Can anyone think of why this wouldn't work?

If I am not mistaken, Jaguar XJ sedans (XJ6 and XJ12) were set up this way. A dash switch toggled the fuel gauge to the left or right saddle tank. The tanks were mounted in the trunk. The same switch toggled solenoid valves for the feed and return. When a return valve died, you could overfill the other tank.

 

[wreckerman893]

Remember the return fuel line.....you need to plumb it to where the tank you are pumping out of is the tank that the excess fuel from the IP is going back to.....otherwise you could be pumping fuel into an already full tank and have a spill.

This means two switch valves.....one for primary line and one for the return line.

 

[rosco]

Most Over the Road trucks with multiple tanks, just use about a 3/4" transfer hose that is plumbed to the bottom side of the tanks. Both tanks stay the same level. It wouldn't matter which tank, the return is to. No extra wiring. Solder in a fitting on your new tank, with an outlet ball valve, pump off the fuel in you old tank, to the new one, while you solder in the fittings, then hook up a transfer hose, between the two tanks.