Petrol Reserve Tap

technical data -

Ewarts reserve changeover valve.


maintenance -

To be written...


problems -

Usually leakage - both from top and bottom of the unit, due to the corks shrinking and therefore needing replacing.

Damaged corks (leading to leakage) due to missing metal inserts or abrasion against particles in the plunger tube.

There is a small brass setscrew which holds the threaded part of the plunger to the brass top. Failure to undo this may result in the thread snapping. The setscrew is liable to seize which may result in damage to the head.

If the unit should become overly stiff due to gummy petrol deposits, the connecting Bowden cable may then be liable to damage (usually the sheath works loose immediately behind the facia).

The split pins holding the moving parts are liable to rusting and snapping.


removal -

1) Unscrew inlet and outlet pipes and drain excess petrol.

2) Detach Bowden cable (clamp to sheath and screw to cable).

3) Remove 2 bolts (top and bottom of unit) into chassis.

If dismantling to replace the corks, be aware that a small setscrew holds the threaded part of the plunger to the brass top.


other notes -

The cork seals shrink, mainly because the petrol has become contaminated with water, has wet the corks and then dried out. They do not usually shrink in regular service.

It is believed the changeover valve of the Lanchester Leda (14) is interchangeable.

Fitting new corks -
The corks are supposed to be a tight fit (ie. are marginally oversize) and may require a tapered 'fitting tube' to assemble corks (especially if slightly swollen) into the valve. Lubricating with engine oil aids assembly, washes away (in due course) and doesn't contaminate the fuel.
The brass spacers prevent overtightening of the stud from squashing the corks lengthways and to allow you to lock the screw, by tightening it against the resistance of the spacers. These are not attached to the corks, but slot inside them. End pressure from the washer compresses the cork slightly, sealing it against the spacer. If a cork is the exact same length as the spacer, then it is too short.
The center screw should be tight enough to bottom out on the spacers, then tightened to the torque that one would normally use for that size of screw.
The valve should (and must!) be petrol-tight when correctly assembled, regardless of position.

In an attempt to find replacements for the cork seals, the following have been tried :-


None yet.