Dual tank switchover

[AndycruiserguyLomas]

On my 100 series which has the auxiliary fuel tank I need to know how it works when switched over. I have run the main tank down to reserve light level and pressed the sub tank button on the dash and hear a clunk from the fuel tank area. What I need to know is how this works as I have no handbook. Does the auxiliary tank have a sender so that when switched over the fuel gauge shows the level, does it fill the main tank or is it separate in its entirety?

I need to know this as I do not intend to run out of fuel when i have got a full auxiliary tank of diesel waiting to be used and don't know how to access it.

This maybe a question for the Aussie lads as this 100 was bought in Australia brand new and shipped to the UK

Andy

 

[chadr]

I thought that a transfer pump was usually involved with auxiliary fuel tanks? So that you effectively pump fuel from the sub-tank to the main tank?

 

[grantw]

This is for an OEM fitment.

Andy I **believe** it does switch the fuel gauge too but I'm sure there will be someone here who knows for sure.

 

[Chris]

That was my understanding. I am about to fit this lot to mine and I got some advice on the set up before ordering the parts. There are several ways you can set up a dual tank system, but on the Toyota (as I understand it) You have a selectable filler neck, then a solenoid valve that diverts the 'suctions' from the injector pump between tanks. This will be the clunk you can hear. You can either have a sub tank fuel gauge or simply splice into the same feed from the main sender with the aux sender. The dash should then slowly start to show the full tank until it stops at the top of the gauge. Remember though that this is showing full to empty, NOT specific litres. If your sub tank is the same capacity as the main tank then happy days. But if it's smaller then don't expect another 500 miles out of it. I also don't know if the orange light works when running from the sub. I am not bothering to wire that in myself.

Chris

 

[Jon Wildsmith]

Don't you have a separate gauge for the sub tank in an overhead console? I thought all the diesel OEM sub tank installs had that, maybe the sub tank was not on when it left the factory? The sub tanks usually have a level sender, that's what I bought to go in my after market tank, the OEM sub sender. You should be able to tell if the main gauge is dual purpose just by watching it for a bit when you switch tanks. The clunk should be change over solenoids that go on a bracket roughly above the rear axle centre to passenger side iirc and as Chris described select which tank the injection pump sucks from.

 

[Julian Voelcker]

Andy,

Assuming it is a straight 100 series the switch should also switch over the fuel gauge and will give you a 'SUB' light on the dash to indicate it is reading from the sub tank. Just be aware it can take a few moments to change.

I can't remember if the low level light will also work or not.

There are usually two solenoids, one for the feed to the pump and one for the return, we use a solenoid that does both at once.

If home wiring the gauges on the 80s are a simple variable resistor requiring just two wires, whereas the 100 series senders have three wires feeding them and usefully the colours are different front and back which makes you scratch your head a bit when fitting.

Most Aussie long range tank kits are designed to just replace the factory sub tanks and use modified versions of the senders which is why the kits are pretty basic. You can get some kits with all the required bits over here but they are a little pricey otherwise you have to make up your own.

The SA kits tend to lean towards the transfer pump arrangement so no solenoids needed and also they tend not to have the fittings for gauge senders.

One note to bear in mind, tanks designed for transfer pumps aren't really that suitable for direct feed, they need to draw centrally and have a bowl inside for counteracting the effect of going round corners.