Practical Classics (UK)
FLATTERY IS GETTING ME NOWHERE
Q I use my Ford Cortina MKIII once a month and it's always a battle to start. Quite often, the battery goes flat while cranking and I have to borrow my neighbour's jump pack and try again. Do you have any tips?
James Smith, Gloucester
A You can help the battery by turning the engine so the points are closed, then switching on the ignition and flicking the points open and shut until you detect slight sparking across the contacts. This removes any oxidation which may have formed and gives a spark at the plugs straight away. A further obstacle is that the fuel pump may not be able to draw petrol through the empty fuel lines to fill the carburettor. This may be due to low cranking speed, a weak pump – or just the height of the pump relative to the tank. The best solution for an occasionally-used car is to install an electric pump, which fills the carburettor as soon as the ignition is turned on.
An underlying issue, though, is that due to lack of use the battery is permanently discharged. It can take up to three days to charge a completely flat battery, and it's likely your battery is almost flat most of the time. Charge it on an old-fashioned charger on the low charge rate over 24 to 48 hours. Do this in a ventilated (or at least, a draughty) space, as it will give off gas for many hours between reaching optimum voltage and becoming fully charged. If the cell caps are removable, leave them loose but still in the holes. In this case use a hydrometer to check the charging progress. When the readings rise no further over some hours, the battery is charged. If the flat battery starts to fizz quite soon after charging starts, it's sulphated and should be replaced.