Series Land Rover Contact Point Problems
The condition and operation of the contact points are of vital importance to the efficiency of a standard Series Land Rover petrol engine. There has to be an electrical supply to the points of course and this is very easily checked by switching on the ignition and then flicking the contact points open with a screwdriver; there should be a visble spark.
If there is no spark seen, then suspect either the primary winding in the ignition coil - best confirmed by sustituting a new coil (good to have a spare anyway). Alternatively, the connectiion from the ignition switch could be faulty - maybe the switch itself or a poor contact.
Having seen a spark,
then the next thing to check is that the points gap is set correctly at its maximum opening - 0.015in(0.38mm) for Lucas distributors and 0.017in(0.43mm) for Ducelier distributors.
If there is a spark at the points and the gap is correct, then check the surfaces of the points are clean, smooth and not pitted. Any imperfection on the point surfaces can reduce the current passing through the coil and reduce the suddenness with which the current is shut off as the points open. The sharper the cut-off of the points current then the higher will be the current going to the spark plugs. Dirty or rough surfaces can be cleaned with abrasive paper as an emergency measure but such cleaning will affect the ignition timing slightly. Care should be taken not to allow abrasive particles to enter the distributor.
If the contact surfaces of the points are rough then check if the reason is because the current is passing the 'wrong way' across the points. For Series Land Rovers with negative earthing the contact breaker wire should pass from the distributor to the (-) marked terminal on the ignition coil. If the coil is of the old style and does not have (-) and (+) marks, then it should go to the CB terminal. Infact if the coil has only SW and CB markings on the terminals then the contact breaker wire should go to the CB terminal even if the Land Rover has positive earthing.
A common reason for the points gap to gradually decrease is because the (usually red) heel of the breaker mechanism is worn down by the central rotating shaft of the distributor. Applying a LITTLE grease to the heal can prevent this.
Previous homepages devoted to the ignition system were
July 2010 February 2011