Petrol Gauge

technical data -

This consists of the cork-float sender unit (mounted in the tank) and the gauge (mounted on the facia).

AC Delco Sender unit (stamped #1519696) resistance (approx.) 3Ω (empty) to 33Ω (full).
Petrol Gauge, (probably) A.C. No. 1519786 or 1519784. 30Ω each coil and 30Ω wire-wound strip between lower coil and BATT terminal.

maintenance -

Should the sender unit seize, it should be well lubricated with light oil and gently persuaded to move after the oil has penetrated. Attempting to force the mechanism will cause it to snap (and this may not be immediately apparent).

Undertake any maintenance or repair of the sender or gauge with extreme caution since both are particularly delicate and prone to permanent damage.

problems -

The metal gearing of the sender is prone to corrosion if neglected and may seize or stick - it may be possible to recover the unit if treated in time.

The fragile sender wiper may snap leading to no reading despite full movement of the float.

The windings/wiper of the rheostat in the sender may fail - check the resistance of the unit.

Intermittent readings may be due to poor earth connection with the sender unit (usually due to corrosion) or faulty wiring (passes along the petrol tank to the O/S, then into the chassis member).

As with the fuel pump, the brass screws holding the sender in place are prone to damage by overtightening and may lead to stripped threads.

On Barker-bodied cars, the screws holding the pressed metal plates (over the sender) will often seize. It may be easier to replace the screws than to repair the plates, or re-weld the captive nuts if damaged.

The wire-wound paxolin strip on the back of the petrol gauge has often experienced extreme temperatures and may be brittle and liable to disintegrate on touch. The enamel-coated wire wound around it may also have experienced damage to the insulation, leading to a short which will reduce the resistance (and thus increase the heating still further). If the paxolin appears darkened and the wire is silver or gray rather than red, this is likely the case. The gauge may then give inaccurate (or no) readings.

removal -

1) Remove plywood center section of boot floor (10 screws, Briggs) or 2 pressed metal plates on boot floor (Barker).
2) Unscrew sender unit (top, N/S of the tank) and (gently) tap to break seal.
3) Remove sender, being careful not to damage the cork float as it is withdrawn.

Access to the sender rheostat is by removal of 3 screws in the sender body.

For fuel sender removal click here Instruction provided by Neil Sharpe (Many Thanks)

other notes -

It is advisable to fit a new gasket when re-fitting the sender unit.

It is believed the petrol gauge of the Lanchester Leda (14) is interchangeable.

It seems the sender float will often 'stick' if tested outside the tank. Whilst in the tank, the gearing is submerged, provided the tank is about one third full, affording sufficient lubrication for free movement. Vehicle vibration probably helps too.

If the wire-wound paxolin strip is damaged, it may be possible to re-lacquer and re-wind it on a new substrate, although this is likely a job for a professional. DO NOT, on any account, replace the wound section with a standard resistor. It will reach approx. 140°C, de-rate the resistor and may lead to premature death or fire.
Should it be necessary to replace the wire-wound section, it is first suggested to cut the wire after the coil, such that the entire 30Ω wire-wound section is removed. Solder the cut end to the BATT terminal (the tag strip to which the other end of the wire-wound section was attached).
The missing 30Ω must now be replaced by power resistors capable of dissipating 2.4W. Ordinary resistors are not suited to this task (hence the original design which spread the heat over a large surface area) and siting the resistor(s) inside the instrument panel is ill-advised. It is recommended that the resistor be de-rated by a factor of at least 2, and ideally 4 - ie. a 10W resistor is an excellent choice.
The new resistor(s) should be attached close to the instrument panel with sufficient air flow (the back of the wooden facia on the Barker is ideal for example). If attaching to, or near, metalwork, take care to ensure no part of the resistor can short to ground, taking vibration into account.
Connect one side of the resistor(s) to the BATT terminal and ALL wiring which originally went to the BATT terminal must now connect to the other side of the new resistor(s).

diagrams -

All images are scanned from originals, wherever possible, at 100dpi (unless otherwise noted) and must be scaled when printed to preserve the original size (eg. scale up by 3 times for a 300dpi printer).

Note, however, that due to slight scaling inaccuracies during both the scanning and inevitably the printing, these images should be taken as an approximation for reference only.
In addition, drawings, measurements and notes of materials used are intended as a guide and aid to the restorer, and not necessarily a definitive, or even guaranteed correct, reference.

The seal between the fuel sender and petrol tank consists of a thick 'woven' fibre material approx. 0.075" thick (this appears to be a slightly thicker version of the fibre dome seal used on the fuel pump).
A suitable replacement can be cut from neoprine sheet and the screw clearance holes punched out.

None yet.