Fuel tank auto-leveling system

[Phormula]

Has anyone thought about a system that could auto-level the fuel in both tanks and save manually switching between the two?

I can think of two possible solutions....

• Replace the existing "fuel tank selection switch" with a simple circuit that would activate then a pre-determined difference is reached between the fuel level of the two tanks.
• A fuel pump that would move fuel from one tank to the other when the difference between the two tank levels reached a set limit.

Option one is the simplest. The inputs could come directly off the fuel guages, so it would be very simple to fit.

Option two would only require a single pump to feed the engine and therefore remove the risk of fuel starvation whilst switching between tanks (if this is currently a problem?).

Any thoughts?

[Steve_D]

Or simply join the two tanks together at the bottom as I and I'm sure a few others have.
Does not then matter which pump or which gauge is running.

Steve

[spatz]

Ultima is offering a tank link cable, at least I have ordered one for exactly this purpose

[Graham-P]

Steve_D said:

Or simply join the two tanks together at the bottom as I and I'm sure a few others have.
Does not then matter which pump or which gauge is running.

Steve

Yep dash 12 fittings joining both tanks and one fuel pump sucking from both tanks.

[qwick]

Hi, like the guys say a balance pipe is a really simple way of doing it. That's what I have on mine, it can apparently take a little more time to fill up but you can use a solenoid to close the pipe off if you want or put up with it dilling the other tank at a slower rate while you fill the first tank.

Edited by qwick on Wednesday 28th January 17:20

Edited by qwick on Wednesday 28th January 17:23

[Graham-P]

spatz said:

Ultima is offering a tank link cable, at least I have ordered one for exactly this purpose

I think you'll find that this is a dash 6 pipe that links the tanks at the top to balance the air, not a link for filling both tanks.

[Phormula]

I'll get my order in with the factory for the tank balance pipe, thanks for the replies

[Graham-P]

Phormula said:

I'll get my order in with the factory for the tank balance pipe, thanks for the replies

Unless I'm mistaken the factory do not sell a pipe to link the tanks for filling, you have to do that with dash 12 or bigger fittings welded to the tank in line with the bottom fittings already there. As I stated above the only link pipe that was available from the factory was a dash 6 to link the tanks at the top to balance the air.
The factory didn't like the link pipe the last time someone enquired.
HTH

[rduart]

Graham-P said:

Phormula said:

I'll get my order in with the factory for the tank balance pipe, thanks for the replies

Unless I'm mistaken the factory do not sell a pipe to link the tanks for filling, you have to do that with dash 12 or bigger fittings welded to the tank in line with the bottom fittings already there. As I stated above the only link pipe that was available from the factory was a dash 6 to link the tanks at the top to balance the air.
The factory didn't like the link pipe the last time someone enquired.
HTH

I think you are correct. I had the factory add a -10 fitting to bottom/side the each of the tanks for the balance pipe. -12 might have been a better option. Time will tell. If you are thinking about using the balance pipe approach, you can ask the factory to make the modification. They did it for me.
Randy

[Steve_D]

I just used -6.
It is not big enough to fuel from one side only but is happy to deal with keeping them balanced under normal driving.
You fill one side then dash round and fill the other. The first side will start to empty so the last stage of getting it topped off is a little slow as the first side re-fills.
Works for me as by that time I'm normally fending off the 20 questions starting with 'What is it?' despite it being written in 4" high lettering down the side.

Steve

[738 driver]

This might be a very stupid question but is it not possible to just T the tanks to a common low pressure feed which includes one-way valves before the T, then you would use fuel from each tank at the same time without fuel transfer during cornering etc?

I'd hoped to adopt this theory myself!

Edited by 738 driver on Wednesday 28th January 20:05

[Steve_D]

738 driver said:

This might be a very stupid question but is it not possible to just T the tanks to a common low pressure feed which includes one-way valves before the T, then you would use fuel from each tank at the same time without fuel transfer during cornering etc?

I'd hoped to adopt this theory myself!

Edited by 738 driver on Wednesday 28th January 20:05

How are the valves going to work?
If they are spring loaded shut then one will be stronger than the other. In which case fuel will only be drawn from the weaker valved tank.

Steve

[738 driver]

I'll look up the name Steve....the type of valve I had in mind was used in a dual tank installation in a water system..and I dont think there was any accumulator-pressure behind the valves, in the main tanks. The system was part of the air-con on a long haul aircraft, water vapour introduced to restore some moisture content for passenger comfort on longer flights.(hardly any moisture in the air at high altitudes so the pax can get sore throats and dry chests due to dehydration)
At the time I saw it I recall thinking it should work in a multi-tank fuel system too.
Will have to dig through mi tech notes for its correct name and maybe a line drawing to show its principle/operation.


Edited to call upon Hackin N Bashin.......I just remembered our own A/C engineer may well know.

Edited by 738 driver on Wednesday 28th January 22:38

[spatz]

ok now you have confused me, I have no problems filling both tanks seperately but I really
do not want to switch tanks (cannot imagine that this makes sense having one tank empty and the other full in trems car balance).
So simple question will the factory tank link level the both tanks so I can have the fuel system connected either left or right ?

thanks

[Pb3]

I went down the electronic route and have a PIC controller. It does many things; 2 speed cooling fan control, Accusump control, dash display and fuel management. The latter allows me to auto-switch based on tank level, it also gives both left and right tank levels, along with an overall total on my display.

[Graham-P]

Here are a couple of pics that Andy sent me when I was building. These are of the system he devised that I copied, they show the link pipe (with black wrap) and then fuel pump.

[Steve_D]

spatz said:

ok now you have confused me, I have no problems filling both tanks seperately but I really
do not want to switch tanks (cannot imagine that this makes sense having one tank empty and the other full in trems car balance).
So simple question will the factory tank link level the both tanks so I can have the fuel system connected either left or right ?

thanks

The tanks have two outlets at the bottom but they are not right at or in the bottom. One has a pipe inside that bends down and almost touches the tank bottom so this is the one used for the fuel feed. The other is just a fitting into the side and this is what I use to link the tanks.

With this setup you can take fuel from whichever tank you like but if the engine is very high powered and is run that way for a long period then the -6 balance (on free flow) may not be able to cope. Personally I think this situation is highly unlikely unless you were at high speed on an autobahn.

Steve

[spatz]

ok thanks, and I assume that this hose for linking is not the one that is mentioned on the ultima order ?

[crafty]

I ordered my tank with -12 fittings all round as I wasn't 100% sure what I was going to do with fuel atthe time of ordering.

If I was ordering now I'd order -12 fittings for the bottom 2 and -6 for the top.

I ended up using -12 hoses at the bottom ....one as a tink link and one with a TEE to the fuel pump

The return from the fuel rail goes to the top connection on one tank.

The overflow on the swirl pot goes to the top connection on the other tank.

[spatz]

ok stupid question, what is a swirlpot ?