22 replies to this topic

[Haynes]

Not having any experience with twin tanks, was wondering how they work together.  I believe there is only one sender and gauge?  Do they operate as one, so when you fill one side up it levels out with the other side?  Or do you have to fill separately and it uses up first one tank then the other?

[Red Riley]

The answer is basically, yes. The sender is on the left hand tank. The pump connects to a tee on the balance tube that runs between the two tanks so that the pump pulls from both tanks at once. If you wait long enough you can fill both tanks from one side, but it's faster to top them both up. The fact that the two tanks level out means that if you park sideways on a steep slope it's possible for fuel to run out of the neck of the downhill side tank.

[mab01uk]

PETROL TANK JOINING PIPE. R/H TANK TO ORIGINAL L/H TANK :-

https://www.minispar...ic/21A2331.aspx

 

RIGHT-HAND PETROL TANK FITTING KIT :-

https://www.minispar...31.aspx|Back to

 

 

Edited by mab01uk, 11 February 2021 - 03:34 PM.

[Ethel]

 The fact that the two tanks level out means that if you park sideways on a steep slope it's possible for fuel to run out of the neck of the downhill side tank.

 

Running the vent hoses to the opposite side above tank level and using unvented caps would help. But we're still talking about Minis 

[Tornado99]

Interesting. Reminds me of having two fuel taps/petcocks on a classic carb'd motorcycle. It is only one tank, but because it needs to straddle the center frame spine, there is a full length divide between the two sides of the tank. So this is managed by having a tap at bottom of both sides. Usually, best practise is to run bike on one side of tank only until it sputters near empty, then reach down and switch over the remaining fuel in other side by opening that side's tap. So you get a reserve "tank". 

 

Modern bikes with fuel injection usually have the fuel pump inside the tank and the pick up pipe is positioned so allow most fuel to be drained from one side....not usually any provision for getting the last bit from other side, just sloshing of remnants side to side. 

 

I was thinking the twin tank Cooper's were perhaps setup this way. 

Edited by Tornado99, 11 February 2021 - 07:05 PM.

[Red Riley]

Remember, there are no dump questions. 

 

 

 The fact that the two tanks level out means that if you park sideways on a steep slope it's possible for fuel to run out of the neck of the downhill side tank.

 

Running the vent hoses to the opposite side above tank level and using unvented caps would help. But we're still talking about Minis 

 

I think the generally accepted way to prevent this is to only run each tank half-full. So much for the benefit of having twin tanks. 

[Spider]

The answer is basically, yes. The sender is on the left hand tank. The pump connects to a tee on the balance tube that runs between the two tanks so that the pump pulls from both tanks at once. If you wait long enough you can fill both tanks from one side, but it's faster to top them both up. The fact that the two tanks level out means that if you park sideways on a steep slope it's possible for fuel to run out of the neck of the downhill side tank.

Great answer here, the only thing I'd add is that it takes a good few minutes (think 10 - 15) for the tanks to level themselves out as it's only a 5/16" line connecting them together. Fine for feeding fuel to the engine, but in all reality, useless for filing from one tank.

The other perhaps hidden benefit of having such a small line between the 2 tanks is it works as a very effective baffle to stop sloshing from one tank to the other when cornering.

[floormanager]

My routine in filling up, is drive up to a pump, anyone that's free, no need to wait for one on the right side of the car.    Get out, remove both fuel caps, start filling the nearest tank to the fuel pump, have the nozzle half out of the tank.  When it clicks off, run round to the other side and fill up the second tank, with the nozzle a bit further out.  When it clicks off, run round to the original tank and top it up.

 

Avoid all the funny looks,   fit the fuel caps and go and pay!! (most important the last part as everyone will have your description)

 

The fuel gauge is a bit silly.

Full  = 2 full tanks

half full = 1 full tank

3/4 empty = 1 half tank

Empty is empty though

Edited by floormanager, 11 February 2021 - 07:32 PM.

[cooperd70]

Since fitting the 2nd tank to mine I have each cap key in certain spots on the keyring so know which is which when pulling up to the filler. As FM said a bonus is that you can pull up to any petrol filler in the station 🙂

Fill up the one side to mostly full and then top up the other side.

It was well worth getting the 2nd tank for a trip onto mainland Europe. Before I'd always had the fear of running out of fuel not knowing where I'd find a station in unknown territory.

Another (minor but important to me) reason for having twin tanks was that I was amazed as a kid seeing Jags etc having both sides filled up at the local garage 🙂

[Cooperman]

When I need the maximum 11 gallons, I just fill each in turn. Very little drains from the full tank to the not full tank durint the time it takes.

The Jag has twin tanks, each exactly 10 gallons, but each has its own fully immersed pump. I had a couple of XJ6's, a 4.2 4-door and a 4.2 Coupe. Once I had one tank reading almost empty and I switched to the other full tank, but the fuel pump failed, so I switched back and drove home with the gauge for that tank reading 'empty'. In the morning it took 9.6 gallons to fill it, so I had 0.4 available (with 10 gallons not available) which is 3.2 pints. Am 4.2 litre XJ6 won't go far on 3.2 pints.  Tank drained, new pump fitted and tank refilled under Jaguar warranty. With all the warranty work which I had done on that 4.2 Coupe I'm sure Jaguar made a loss on it!

[Spider]

Since fitting the 2nd tank to mine I have each cap key in certain spots on the keyring so know which is which

 

You can get caps on a single common key

[floormanager]

Another (minor but important to me) reason for having twin tanks was that I was amazed as a kid seeing Jags etc having both sides filled up at the local garage

Exactly the same as me, always wanted a car with twin tanks since watching Jags fill up as a kid.  I just thought I was the only weird one!

[floormanager]

 

Since fitting the 2nd tank to mine I have each cap key in certain spots on the keyring so know which is which

 

You can get caps on a single common key

 

Now that would be useful, though for now, I've gone back to the original unlocking type.  Have the locking ones for when leaving the car somewhere.  Where can you get single key fuel caps?

[cooperd70]

Since fitting the 2nd tank to mine I have each cap key in certain spots on the keyring so know which is which

You can get caps on a single common key

Well I didn't know that! Having said that though I did find a year specific cap and key on fleBay in amazing condition to match the LH tank...so I'm happy 🙂

[cooperd70]

Another (minor but important to me) reason for having twin tanks was that I was amazed as a kid seeing Jags etc having both sides filled up at the local garage

Exactly the same as me, always wanted a car with twin tanks since watching Jags fill up as a kid. I just thought I was the only weird one!

LOL - well there are at least two of us on here ...tho' I have a feeling that there are many many more 😬😬👍👍