One baffling mystery is the change over switch on the dash. I thought it'd be as simple as 'changes tank A to tank B and switches the fuel gauge' using a push switch that appears to have two active circuits (4 wires) meeting in either of the two positions. It is faulty or baffling.

rather than an even 12v I get an oscillating spaz of volts between .5 and 11.8.

i can power the wire to the tank using the lighter (+) and it works.

wires I have here

white with purple stripe (right pump)
white with green stripe (left tank)
white (ignition control circuit, unfused)

lightgreen with red stripe (change over right)
lightgreen with orange stripe (not sure but power to this pushes the fuel gauge up to 50% full......????)
lightgreen with skate stripe (change-over left)

I assume that when the list says 'to change over and 'switch to change over' etc well its not worded right. from experimentation I can see the white wires feed the pump power but what the lightgreen have to do with change over isnt clear I assume swapping the gauge?
but I can't follow what does which in what combination, esp if I do have a fault causing this erratic voltage reading.

any helpful hints here? wiring diagrams are like Arabic to me.

 

lt green red LGR (fuel tank changeover LHD) lt green slate LGS (fuel tank changeover RHD)white purple WP (fuel pump)white green WG (secondary fuel pump)white white W Mk2: unfused ignition coil circuit; fuel pump





lt green orange
NOT USED
another on line list gives these, noting that the last one says the wire is not used yet i get response from the fuel gauge on it
yet another classes the lt green/orange as "Rear window wash switch to wash pump; or cab lock-down switch to warning light"

 

... but always check the inertia fuel cut off valve first.....

 

I am more familiar with the Fuel Injected models from 1978 onward. I think the scheme is the same for the carburetted engine cars. I just don't see many any more.

Fuel injected models only have one pump so there is a fuel changeover to the pump.
The 3 changeover valves are normally set to the LEFT tank with NO power to the valves.
When the switch is set to the RIGHT tank, power is applied to ALL 3 valves and they change state.

The fuel supply valve is OPEN to the LEFT tank with NO power.
The fuel return to the LEFT tank is OPEN with NO power.
The fuel return to the RIGHT tank is CLOSED with NO power.

When the switch is set to the RIGHT tank, ALL solenoid valves CHANGE STATE and fuel is drawn and returned to the RIGHT TANK.

The switch also directs the correct sender to the gauge.

The Carb cars will send power to the correct pump as well as input from the senders but the return valves should be wired the same as the fuel injected.

Here is a .pdf that I found. I think someone on this forum uploaded it.
Thank You whoever it was???

bob