Points Servicing – 25D Distributor was originally published in Practical Motoring magazine.
The Lucas 25D distributor which is the basis of this feature is used on a number of small British cars. In particular those from British Leyland and some of the small Chrysler models. This doesn’t mean however, that the distributor from one car can be removed and fitted to another of different capacity. Although the basic type may be the same, there will be important detail differences which control the ignition advance curve. Only units having the same type number and also the same identification number (stamped on the distributor body) are truly interchangeable.
Since this is a generic article, use of the Haynes or Original Workshop manual is recommended.
Some people love points, the car generally won’t die completely with points issues. Still you may want to consider an electronic ignition solution and keep points as a backup. for the 25D refer to an article here on the step by step to install a Pertronix electronic ignition.
Nevertheless, the points service described here will vary little from model to model.
Overview #
The first step, obviously, is to remove the distributor cap. And now would be a good time to have a close look at this item. First make sure it is clean —both inside and out. Check the centre carbon contact. If it is worn or chipped, or the spring Is weak, the contact and spring can be renewed. Check the plug lead contact posts. These may show some oxidation, but If badly burnt you need a new cap.
If the bakelite cap has any cracks it must be renewed. It must be renewed also if there are any signs of tracking. This problem is shown by a hairline of jagged (lightning) form running from one of the HT posts to some point where it can find earth — usually on the rim of the cap.
Step 1 – Rotor Removal #
Now remove the rotor arm. Make sure there are no cracks or signs of tracking on the plastic — like the cap, It should be renewed If unsatisfactory.
The tip of the rotor will show traces of burning similar to those on the contact posts. Provided this is not excessive it can be Ignored, otherwise renew the rotor.
The tip of the rotor and the HT contact posts must never be cleaned with any abrasive or by scraping. Such action will Increase the gap between the rotor and posts, and could cause misfiring.
Step 2 – The Points #
This distributor may be fitted either with two-piece contacts left, or one-piece contacts right. The more common are the one-piece.
Step 3 – Remove Retaining Nut #
Undo the nut and lilt off the special washer securing the LT terminations and the end of the moving contact spring.
Step 4 – Remove Adjusting Screw #
Remove the adjusting screw which also secures the fixed contact to the baseplate.
Step 5 – Lift Moving Contact #
Lift off the moving contact on two-piece contact sets
Step 6 – Insulating Washers #
Note the positions of the insulating washers arrowed and lift out the fixed contact
Step 7 – LT Leads Good Contact #
It is most important when fitting the new contacts that you ensure the LT leads make good contact with the spring. Mount the parts as shown — the special sleeved insulating washer immediately under the nut prevents all three items from earthing on the post.
Step 8 – Securing Screw Fitting #
Fit the securing screw “A” but do not tighten. Turn the engine until the heel on the rubbing block is on the peak of one of the cam lobes.
With a screwdriver located in the notches adjust the gap with a feeler gauge to the setting given in your owner’s handbook (usually 0.01in. on this distributor)
Step 9 – Lock the Points #
Lock the points by tightening the screw “A” and recheck the gap (9).
Finally, smear a very small quantity of lithium based grease on the cam, making sure that none gets on the points. Refit the rotor arm and then the distributor cap.
Hopefully this is a useful article for Points Servicing – 25D Distributor
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