Installing the 80 Factory subtank into an 80 series.
The Toyota Factory subtank has a 50 litre capacity (13.2 US gallons - mine seems to take 14 US gallons on a fill from empty). Not a huge capacity - but a welcome addition to the smallish main tank.
In search of some additional fuel capacity I looked into the large Oz aftermarket tanks, but all appear to 'hang' down too low for my comfort. Given the 80's articulation prowess, I just felt that anything that hangs down below the chassis rails at the rear would be just waiting to be smacked by a nasty rock at some stage.
Given that, the factory subtank sits nice and high (it in fact sits above the spare tyre support crossmember) and is very unlikely to ever be compromised.
Before we start the installation, the following should be noted:
As far as I know the US 80 doesn't have the necessary ECU to control the subtank's fuel pump. In the Oz spec 80 the fuel pump will automatically shut off if either the sub tank runs dry or the main tank is full. I had to provide my own scheme to transfer the fuel - see below.
The 4 captive nuts in the body do not exist on the US 80. I had to drill two holes into the rearmost ribs and install captive nuts. The front most ribs had the holes but no captive nuts - I had to install those too.
This picture shows the USDS of the rear rivnut after installation, the USPS is similar. The hole on each rib must be drilled for the rivnut. A Unibit step drill makes a neat job of this. Installation is easy due to the reasonable access available for the tool.
The following shows the USDS rivnut after installation. The hole for this rivnut was already present in the body - fortunate since drilling it would have been quite a challenge - it sits above the chassis crossmember. You can also see the two captured nuts in the body rib that are used to support the fuel pump and solenoid bracket assembly.
The following shows the USPS rivnut after installation. Again the hole was already present, but installation of the rivnut was a bit of a challenge due to the restricted clearance between the body rib and the chassis crossmember. Careful selection of the bolt length to use with the tool is essential to ensure not getting yourself locked in - i.e. rivnut installed and bolt impossible to remove ;-) Even then I ended up using a crowbar to push the body away from the chassis just enough to get the bolt I used out...
The following picture shows the dual filler. Push the knob in (the normal position to close the fuel lid) selects the main tank, pulling the knob out selects the sub tank. The hose diameter for the fuel outlets is 1 5/8" (ID) and the breather inlets is 1/2" (ID). I could only find 1 3/4" (ID) gasoline rated hose locally. I double clamped each end of the hose to ensure the hose was well sealed to the hardlines. The tank came with all the hardware to fit it - including a replacement filler shroud with the hole to allow the knob and rod to fit through.
