The ignition on a 2CV uses a wasted spark system – that is the spark plug fires on both ignition and exhaust strokes, the latter being wasted. This means that there is no distributor, it uses a low tension circuit breaker driven off the cam shaft to fire the spark.
As well as the circuit breaker the points also include a capacitor (know as the condenser) that resonates with the resistance in the coil to induce a high tension across the spark plug gap.
Over time the contact surfaces wear, as does the plastic cam follower, meaning the gap between the points at the fully open position reduces making the spark less efficient. Replacing the condenser and adjusting the gap is an item on the D (yearly) service list. If the contacts are excessively worn then they also need replacing and the gap setting.
First remove the fan and the rubber points protector – the latter is held on with 8mm bolts, I found a 1/4″ drive was best to get purchase on them given some of the tight clearances.
With these removed the points box is easy to access. If you are replacing any items then the box will need removing. Disconnect the spade connector at the lower right hand side and undo the 11mm bolts on either side and remove the box.
The box cover is held on with three screws, remove this first. Then remove the condenser which is held on by one screw to the left of the box and the contact screw that goes through the condenser connector, the spade connector, the insulator and secures into the spring blade mount. Carefully remove all these items and the lower (moving, positive) contact arm paying particular attention to how they fit together. The top (fixed and earth) contact arm is attached to the points box with a flat head screw that locks it into position, remove this and the top contact.
Re-fitting the new parts is the reverse of assembly:
Fit the top contact to the box leaving the screw lose. Hook the spring blade into the lower contact and place the mount into the insulator’s trough. With these three parts as a unit place them back into the points box.
Fit the condenser into its insulating mount and thread the contact screw through (in order, bottom to top):
- Condenser connector
- Spade connector (pointing up)
- Condenser’s insulating mount
- Points box
- Insulator trough
- Spring blade mount
Replace the earth screw attaching the condenser to the points box and, without replacing the cover, re-attach the points box to the car – the exact position isn’t vital as that will be determined when you re-time the ignition.
Using the 14mm fan retaining bolt screwed into the fan taper rotate the engine until the lower contact is fully open on the heel of the cam. Place a 0.4mm feeler gauge between the contacts and tighten the top contact retaining screw locking it into position ensuring there is a slight drag on the blade of the gauge. Rotate the engine again so the lower contact is open again on the other lobe of the cam and check the gap is still correct.
Replace the points box lid and seal, then re-time the ignition.