Two different types of Lucas distributor are,used on Mini models; the 25D4 type and the 45D4, the latter being the more recent fitment. Although both of the same basic design, they differ slightly in some details and thus require slightly different maintenance procedures.|
The 25D4 type can be identified by the cast housing on the distributor body for the vacuum unit spindle. It also has the terminal for the low tension lead mounted in an insulated block on the side of the body, whereas on the 45D4 unit the LT lead comes directly out of the distributor body and has a remote Lucas connector on the end of the lead. This latter type distributor has a detachable vacuum unit which is secured to the body by two screws.
Some Mini 1000 export models may be fitted with a 43D4 type distributor which is a variation of the 45D4, but without a vacuum advance unit.
The distributor should be lubricated at the specified intervals and when renewing the contact breaker points.|
Remove the rotor arm and apply one or two drops only of light oil to the felt pad (45D4) in the end of the distributor cam spindle, or around the spindle centrescrew (25D4). refers. Similarly, apply a few drops of oil through the gap between the contact plate and the cam spindle to lubricate the centrifugal weights. On the 45D4 type distributor, do NOT oil the cam wiping pad.
Every 24,000 miles (40,000 km), add a further drop of oil to the two holes in the base plate to lubricate the centre bearing.
Smear the contact surface of the distributor cam lightly with suitable high melting-point grease or petroleum jelly. Also apply a very light smear to the breaker arm pivot post.
Do not overlubricate any part of the distributor. Take great care to avoid getting oil or grease onto the contact points as this will cause burning of the points surface with consequent bad starting. Wipe away any surplus lubricant and ensure the contact points are clean and dry.
|Contact Breaker Points - Lucas 25D4 Type Distributor||
Remove the ignition shield, where fitted. Remove the distributor cap and rotor arm and examine the distributor points.|
Points which are worn or badly burned should be renewed. If contact breaker points are badly worn and have a 'blue' appearance then it is likely that the condenser needs replacing.
In most cases it will be more expedient to fit new contact breaker points rather than attempt to clean up the existing ones.
To renew the points, first remove the nut from the top of the terminal post and lift off the top insulating bush and both electrical leads . Remove the screw, spring and plain washer securing the contact set to the base plate and lift out the contact set. Take great care to ensure that none of the components are dropped down inside the distributor body as, if this happens, the distributor must be removed to retrieve them.
Before installing the new contact set, clean out the inside of the distributor thoroughly. Wipe clean the contact surface on the breaker cam. Also wipe clean the contact faces of the points on the new set as these are normally coated with preservative. Methylated spirits is ideal for this purpose. Do not use petrol, as this is oil-based.
Position the new contact set on the base plate and secure with the locking screw and washers. Tighten the screw only lightly at this stage. Locate the condenser and LT lead terminals onto the top insulating bush and fit the bush over the terminal post so that the terminals make contact with the breaker arm spring. Refit the retaining nut and tighten securely.
Ensure that the lead terminals are properly positioned so that they are insulated from the terminal post.
Lubricate the distributor cam, cam spindle and points pivot as detailed above.
Check that the contact face of the fixed and moving contacts are parallel to each other, aligning them correctly if necessary.
Turn the engine over by hand until the rubbing block on the breaker arm is resting on the top of the cam lobe. Adjust the position of the fixed contact by moving the contact breaker bracket until the specified gap of 0.014 0.016 in (0.35 - 0.40 mm) is obtained between the contact points.
The fixed contact bracket can be moved by inserting a screwdriver into the notched hole at the opposite side of the plate and turning the screwdriver clockwise to decrease the gap, or anti-clockwise to increase the gap . The feeler gauge should be a neat sliding fit between the contacts.
When fitting new points it is advisable to set the gap to 0.019 in (0.48 mm) to allow for initial bedding in of rubbing block.
When the gap is correct, tighten the locking screw. Turn the engine over until the rubbing block is on the opposite cam (180') and recheck the clearance.
After fitting new points or adjusting the points gap, the dwell angle and ignition timing should be checked as described below.
|Contact Breaker Points - Lucas 45D4 Type Distributor||
The contact breaker points on the 45D4 distributor should be inspected in a similar manner to that described for the 25D4 type above. However, the procedure for replacing the contact set is slightly different as the condenser and LT lead are connected to the set by means of a common terminal plate . To release the plate, press the breaker arm spring away from the insulating block and unclip the plate from the hooked end of the spring.|
When reconnecting the terminal plate, slide it into the end of the spring, then position the spring on the insulated block between the two locating shoulders.
To adjust the contact gap, insert the screwdriver into the notched hole on the contact plate and lever against the pip provided on the back plate. In this case, turn the screwdriver clockwise to increase the gap, or anti-clockwise to decrease it.
For maximum efficiency and economy the contact breaker points setting should be checked with a dwell meter. Its use is particularly important in the case of used points where metal transfer has taken place between the points making accurate checking difficult using feeler gauges.|
Relatively inexpensive units are available from most good accessory shops, and in some cases can even be hired.
The dwell angle of the ignition points is the angle of point closure. The wider the points gap the smaller will be the dwell angle, and vice-versa.
The specified limits for checking the dwell angle are: 25D4 distributor .... 60' +/- 3'. 45D4 distributor .... 51' +/- 5'. If the reading is outside these limits, it should be reset as near as possible to the mean.
With new points it is good practice to set the dwell angle to the lower limit as the angle will increase (gap will reduce) as the points rubbing block beds-in.
Connect the dwell meter in accordance with the manufacturer's instructions. Start the engine and run it at idle, then read off the dwell angle indicated on the meter. If the reading is outside the checking limits above, remove the distributor cap and rotor arm and adjust the contact breaker points to obtain the correct setting, while cranking the engine over on the starter.
As a check on the distributor condition, make a second reading with the engine speed increased to about 2,000 rpm. The needle of the dwell meter should then not deviate from the previous figure by more than +/- 1'. A larger deviation indicates that the distributor shaft is worn.
When the dwell angle has been adjusted, the ignition timing must be reset as detailed below.
|Distributor Cap & Rotor Arm||
Thoroughly clean the distributor cap, inside and out, with a clean cloth, paying particular attention to the spaces between the metal electrodes inside the cap. Check that the electrodes are not excessively eroded, and that there are no signs of tracking. Tracking is visible as hairlines on the surface of the cap and is caused by the HT voltage shorting between the electrodes or the central brush and an electrode. Once tracking is present it cannot be eliminated and the cap must be discarded. Also check that the small carbon brush in the centre of the cap is undamaged.|
Similarly, clean the rotor arm and inspect for damage or excessive erosion of the electrode. Also check that the rotor is a neat sliding fit on the distributor spindle without excessive side-play.
Clean the outside surface of the central tower on the ignition coil and check for signs of damage or tracking.
Wipe all grease and dirt from the HT leads and check the leads for signs of cracking, chafing, etc. Ensure that all connections at the spark plugs, ignition coil and distributor cap are secure, and the moisture seals at each end of the HT leads are firmly in place.