Austin Champ Fuel Gauge System
FUEL GAUGE SYSTEM|
This page is the practical side of fixing a misbehaving fuel gauge, for an in-depth article by Andy Jackson, including fixing and history, Andy's article
The problems with the fuel gauge on the instrument panel can be:
The fault of the gauge only working on any third, or two thirds, of the gauge is because the fuel
gauge system is three separate systems in one.
HEALTH & SAFETY
WIRING DIAGRAM OF THE FUEL GAUGE SYSTEM.|
The power starts from the Distribution Box (bottom right), through the INS (Instruments) wire to the Switchboard (top right), note INS LINK. From the Switchboard to the Instrument Panel (IP). From the IP as the + FUEL wire to the fuel gauge sender in the petrol tank - on the diagram it has FUEL GAUGE, whereas it should be, Tank Sender Unit. Note: on the wiring diag. the sender unit terminals are; + (plus) and - (minus), - but on the actual sender unit they are; +6 (plus) and -7 (minus).
|(below) Looking into the rear of the Champ with the winchwell cover removed. The fuel sender unit wires go into the metal tube and up to the back rear of the Champ.|
|(below) The electrical unit. The terminals from the top are, 3, 2, +6, -7, 1.|
|(below) The underside of the electrical unit: the blue arrows show the two contacts that connect to the Torroidial Ring, these are often called, 'wings'; the red arrow shows the Bakelite tab that the pin on the tank unit goes into; the green arrow shows the lug that positions the electrical unit on the tank unit.|
|(below) Contrast the New Old Stock unit above with the one below. Look at the tips of the wings and, below, they are worn through.|
|(below) The top of the tank unit that the electrical unit fits into. Note the pin that has to mate with the arm on the electrical unit.|
|(below) The tank sender unit. The dimension between the top and bottom casting is 13mm, on other military vehicles the dim. is different.|
The fuel gauge does not work at all.
The instrument panel is, or should be, sealed so it is less likely that the gauge itself is faulty.
But, if looking at the instrument panel you can see rust and deterioration on the fuel gauge and
speedo etc., then corrosion in the fuel gauge could be the problem.
The easiest place to start is at the back of the driver's side corner of the Champ where the rear wiring is. Find the + (positive) wire and pull out the connector (a Lucon type) - these connectors do corrode and can be the problem.
Switch the ignition on and use a voltmeter and check for 24v (24v is the nominal voltage but the reading will be the battery voltage, which should be just over 26v), if there is no voltage the problem is toward the front of the vehicle. If there is voltage then the problem is from the connector to the fuel sender unit.
No voltage at the rear corner:
If there is voltage at the rear corner:
Put the voltmeter red wire on the +6 terminal and the black on the -7 terminal, there should be 24v. If not, try the voltmeter between the +6 terminal and a bare part of the Champ body. If there isn't power then it is a wiring fault between the back corner of the Champ and sender unit.
If the voltmeter shows power between +6 (battery main) and -7 (negative) try the mulitmeter on each of terminals 1, 2, & 3 and one of them should give a voltage reading depending how much fuel is in the tank. If any of one of the three terminals does give a reading, but the fuel gauge is still not reading, then that terminal wire is faulty from the sender unit to the instrument panel, check all connections with the voltmeter starting at the back right corner.
To fully test all three segments the electrical unit needs to be removed from the tank by removing
the six screws, which could be seized. The electrical unit itself can only be fitted back in one
position because of a lug on the unit but, try not to move the wiper arms as it comes out because
its best to mark the position of the brown Bakelite slotted tab that locates on the pin in the
actual tank unit so it can be put back in the right place.
If the fuel gauge works OK then the problem is in the tank unit. Before removing the tank unit
(sometimes called the, 'float unit', don't forget, earthing yourself and each tool as you are about
to use it and the fire extinguishers, its preferable do this job outside - another alternative is to
drain the petrol tank but there will still be fumes in it.