Leyland P76 Owners 2007

MINI-TECH TIP TIME

Fuel gauge tips

from The Leyland Post Leyland P76 Owners Club of NSW July 2003.

A recent phone call from a country member had me diving into my incomplete files of old newsletters looking for an answer to an annoying P-problem;
Flickering (or dead) fuel gauge needles!
If you've ever pulled a sensor out of a P76 fuel tank, you'll know that the fuel sensor has a little pivoting arm thingy, which is connected to a little plastic float thingy.
As the level of fuel in the tank changes, the little float thingy rises and falls, moving a little spring-loaded contact across the face of a resistor winding which is mounted in the sensor body, causing a change in the amount of current/voltage flowing through the fuel gauge, and this makes the fuel gauge needle move up or down.
In most cases, the needle flickers because the little spring loaded contact on the pivoting arm thingy falls to make contact with the resistor windings right across its full range of travel or movement, and when it breaks contact, an open circuit results, and the fuel gauge needle then goes berko.
This can happen a lot when the tank is only about half full, and the vehicle corners quickly, because the fuel tends to slosh from side to side.
Try this quick test:
1. Get a helper to turn the ignition key to the 'on' position, and watch the fuel gauge.
2. Get under your P and disconnect the green wire from the fuel tank sensor unit.
3. Firmly earth the terminal of that wire to the vehicle's chassis.
4. Get your helper to watch the fuel gauge needle and tell you what it does.
5. The fuel gauge needle should move right to the top end of the dial.
6. Remove the green wire from earth contact, and the needle should move right back to the left, (bottom) end of the dial.
If the needle doesn't move at all when the green wire is earthed to the vehicle's chassis, then you may have a dead fuel gauge.
It is also quite possible that the green wire has become unplugged, if any heavy objects have been moving around in the upper portion of the boot, so check under the carpet at the front of the upper boot floor to make sure that the green wire is still firmly plugged into the sleeve connector.
The power to operate the fuel and temperature gauges comes direct from the terminal on the back of the ignition switch. Both gauges are designed to work in a series circuit; that is to say that the power flows through each gauge, and goes to earth via the respective sensors.
The temperature sensor is mercury-filled (so I've been told), and the fuel sensor, as already mentioned, uses a swinging arm and contact to vary the resistance of the current going to earth, to make the fuel gauge give different readings.
If the fuse for the brake lights/ignition controlled functions has blown, you will probably have dead temperature and fuel gauges as well as a lack of brake lights.
I have found that a quick fix for flickering fuel gauge needles is to carefully dismantle the sensor, and bend the little springy contact arm thingy to put it under more tension, so that it presses more firmly against the resistance wiring coil thingy.
Then carefully reassemble the sensor, making sure that the little springy thingy is correctly located on the swingy arm contact thingy.
If all this is getting too technical for you Buy a Toyota!
Last updated
May, 2007
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