MINI Cooper cars can experience several common faults and failures at start-up, including problems with the starter motor, the engine control unit (ECU) and sensors, the wiring and the immobiliser. The starting system is comprised of the battery, ignition, neutral safety switch and starter solenoid.
If the lights work and the car starts after using jump leads, there may be a starter motor problem that can be intermittent in nature and caused or exacerbated by damp weather. The starter motor may need to be replaced, but this can get expensive so consider your options carefully. Even when the motor has been replaced, some drivers continue to experience problems, which require accurate diagnosis and repair.
ECU and Sensors
Newer cars are equipped with ECUs. This is a centralised control unit that takes charge of all the smaller electrical circuitry in the car. According to Cars Direct, this component is the car's personal computer. Perform your own diagnostics or take your car to a local garage to find out if this might be the source of the car's start-up problems. Replace the ECU and its sensors if this appears to be the area at fault. Faults with sensors or the ECU are easily identified by the "Check Engine" light appearing on the dashboard.
Check the car's ground wire from the chassis to the lug on the engine. If this becomes loose, the car can have trouble starting and intermittent electrical faults, such as issues with the dimmable lighting circuit. Check all battery connections additionally to ensure you cover all possible sources of failure.
The MINI Cooper is equipped with a component called the "EWS3-Steuergerat box" that is hidden under the dashboard near the front driver's side wheel arch. The wiring and circuitry inside this box control the immobiliser, which can affect start-up if it's not functioning. A small switch in the box is designed to click into place at start-up; but if there is no switch movement, the engine will not start dead. You'll need to replace the box or have a mechanic check the wiring for you.
It might sound basic; but if the battery cannot hold a charge, the motor won't start, and the car's lighting system will give you the first telltale sign. If your headlights go dim or don't light up at all when you switch them on, you will likely need a battery replacement or at least a recharge of the old one.