Dear Frosty,
The cold weather certainly causes some grief for us Mini drivers and not just because of the inadequate heater (Did you know that the heater installed in Australian Minis is larger than the one installed in UK Minis !). Starting problems can be divided into two categories - tuning and electrical.
Iâll deal with the tuning problem first because itâs the simplest. Basically if you engine is out of tune you will have problems in cold weather. An out of tune engine typically will crank over and occasionally fire but wonât start or runs very roughly until warm. Often the engine will become flooded while attempting to start. The A series engine likes a lot of choke when starting in cold weather so its important that the choke is adjusted correctly to give sufficient enrichment and to increase to idle speed. If the enrichment by the choke is insufficient then the engine wonât start straight away and will become flooded as it is continuously cranked. Another area to check is that the dampener oil level on the SU carburettor. When there is insufficient oil in the dampener the engine will fire but the rapid increase in air flow through the carburettor will cause the piston the lift up quickly. This will cause the mixture to lean out. and subsequent cylinders wonât fire to keep the engine running.
Electrical problems are typical of an engine that wonât crank or cranks very slowly. When electrical problems strike the accusing finger is most often pointed at the battery but in reality the battery is not usually the problem. Apart from a flat battery because you forgot to turn you headlights off, the main electrical problems you can experience are inadequate charging of the battery, corrosion of the battery terminals, and a faulty starter motor.
Inadequate charging of the battery occurs mostly during winter due to the increased load placed on the electrical system. A battery that goes flat over a period of about a week is symptomatic of this problem. You may notice that your headlights gradually get dimmer and if your Mini was fitted with an ammeter, it would show a continuous drain on the battery. Inadequate charging is usually a result of a faulty alternator. The extra load from lights and the heater can overload a faulty alternator and cause the inbuilt regulator to shut it down so the car runs on the battery only.
A faulty alternator can be quickly diagnosed by measuring its output under varying amounts of load. Alternators require specialist tools to repair so the only option is to replace it. The other possible cause of inadequate charging is a loose fan belt. A heavy load placed on the alternator makes it harder to turn and so a loose fan belt will start to slip. The slipping fan belt reduces the output of the alternator and the battery is slowly drained to make up the extra power required.
Corrosion around the battery terminals is common during winter because of the increased dampness. The corrosion builds up between the battery terminals and the clamps and forms an insulating barrier between the two. This problem is typical in a car when the electrical system appears to be dead or dies when a load is placed on it. For example the ignition lights and radio will work but everything dies when the start is engaged or the headlights are turned on. A voltmeter connected across the electrical system will show a normal 12 volts when no load is present but will drop to 3-4 volts when a load is added. Corrosion is easily removed with a wire brush and can be prevented by smearing the battery terminals and connectors with a thin coating of vasoline.
A faulty starter motor is typical of a car that has a fully charged battery that appears to go flat rapidly when the starter motor is engaged. After about five minutes the battery will appear to have regained its charge It is typically an intermittent problem that most often occurs damp mornings. This problem is caused by a breakdown in the insulation of the starter motorâs windings. On damp mornings moisture causes the windings to short out and results in the starter motor drawing a heavier load from the battery. This overloads the battery causing it to appear to be flat. After about five minutes the battery recovers from the overload. This problem can be differentiated from the corroded terminals problem by seeing what happens when a heavy load is placed on the electrical system. If the terminals are corroded then any heavy load (ie the lights) will cause the electrical system to die but if the starter motor is faulty only the engaging the starter motor will affect the electrical system.
