You should avoid jump starting a BMW E30 if at all possible. The E30 is part of the BMW 3 series, manufactured from 1982 until 1994. Jump starting an E30 can cause damage to electrical components, such as terminals, fuses, cable ties, batteries, bulbs and lead lamps. Disconnecting the battery and charging it is suggested. Unfortunately, events can strand you by the side of the road and jump starting your E30 could be your last resort.
Park the cars close enough together so that the jump leads will reach but far enough that the vehicles are not touching each other.
Consult your BMW E30 owner's handbook to determine the location of the battery. The location will vary depending on the vehicle model. The battery can be found in the engine compartment, under the rear seat or in the rear luggage compartment.
Turn both ignitions to the off position. Confirm that all electrical equipment is in the off position in the BMW E30.
Clamp one end of the positive jump lead to the BMW E30 battery's positive terminal. Jump leads have a set of clamps coloured red and/or marked with a plus symbol for positive (+) and coloured black and/or marked with a minus symbol for negative (-).
Clamp the other positive end of the positive jump lead to the working battery's positive terminal.
Clamp one end of the negative jump lead to the negative terminal of the working battery.
Clamp the other end of the negative jump lead to the engine block of the BMW E30. This grounds the connection to protect against a power surge.
Start the engine of the car with the working battery.
Start the BMW E30. Check your connections and adjust them as needed if the car does not start.
Remove the cables in the opposite order they were attached.
Run the engine of the BMW E30 for at least 20 minutes to allow the battery to recharge.
Make sure that the working battery is the same voltage as the BMW E30. If the car does not start after all adjustments have been made you may need to replace the battery or alternator. Reduce the chances of a power surge by switching on the fan at its highest speed, rear window defroster and headlights before disconnecting the jump leads. Make sure there are no energy leaks by checking that all lights are off and the boot light has not been left on.
Do not to touch the two ends of the cable clamps together. Do not touch a negative clamp to a positive terminal.