Wow, are we electrified today

When the motor tends to start bad, usually the ignition is responsible. There are many cars out there where the ignition wasn't adjusted since centuries. To get the motor back into the real life it is recommendable to begin the maintenance work with an ignition job.

We will start here with some theory to understand how the ignition works - it's not only mystery.

How a spark is created

To create an electric spark, we need a very high voltage - up to 20,000 Volt. The alternator in the car delivers only 12V. To reach this high voltage we have to use a trick - a coil is used. An electric current is sent through the coil, which creates a magnetic field like an electric magnet. This magnetic field is nothing but stored energy. To convert this energy back in electricity we have to interrupt the current. This is the job of the points. Now we could start to calculate the level of the voltage due to the inductivity formula - or we can simply forget about it. The physical effect can be simplified. Whenever the strength of a magnetic field in a coil changes, it induces an electrical current in the coil. When the magnetic field increases, the resulting current itself creates a magnetic field that is weakening the initializing field. If the magnetic field is reduced, the resulting current creates a field that tries to keep the original field up. When the points open the initializing current will stop. This makes the magnetic field collapsing completely. The result should be a current. But since the points are open, no current can flow. This makes the voltage rise high. The coil is also a transformer. The ratio between primary and secondary side is very high. If the ratio is 100 this means that a voltage of 200V on the primary side will be transformed to 20,000V on the secondary side.
When the voltage is high enough, a spark fires on the spark plug. With the spark we have a current again. This means the stored magnetic energy is now converted back into electrical energy.
Together with the condenser the coil creates a resonance cycle. The energy will now be transferred from the coil (magnetic) into the capacitor (electric) and back. The spark burns until the energy transfer between coil and capacitor runs out.

Now to the practical use

For the ignition we have to adjust 2 parameters. The time while a current will charge the coil with magnetic energy - the dwell, and the moment when the spark should fire inside the cylinder - the timing.
The compressed gas needs some time to ignite. As soon as the piston reaches the upper dead center the explosion is needed to drive the piston down again. To compensate the delay between the moment of the spark and the moment for the gas to burn completely, the spark has to be sent a bit earlier. The right moment to fire the spark is 8° before the piston reaches the upper dead center.
When the motor runs faster, the time it needs to turn 8° is shorter. Since the time between the spark and the explosion is almost constant, the spark needs to be sent a little earlier depending on the speed of the motor. To compensate for this the motor needs a dynamic pre-ignition. In the 2CV motor this adjustment is done via the cam advance weights. Due to the speed of the camshaft the weights will be pulled out turning the cam, which changes the angle to the direction of advanced timing.

Adjustment

To replace and adjust the points the fan has to come off first. The cooling fan grill usually doesn't create problems. The fan pulley is held on the crankshaft by one bolt size 14mm. You have to find a tool that fits into the fan pulley to undo the bolt. With a little luck your 14mm socket will already fit. To undo the bolt the motor must be blocked. A screwdriver held into the gear on the flywheel can easily do this. Once the motor is blocked it is easy to undo the bolt. Mostly the fan pulley sits very tight on the crankshaft. The front end of the shaft has a cone shape, which makes the fan pulley to sit even tighter. To pull it off Citroën had a special tool in the catalog. Unfortunately the tool did not work proper and it isn't available anymore since many years. A better way to get the pulley off is a simple steel pin, which is turned down to the diameter of the fan pulley.

Sketch for tool; dimensions in mm

For removal, the fan pulley has to be positioned in a way that the claws for the crank handle are located horizontal. The pin now goes into the pulley. Hold the pin firmly and smack it with a hammer. Don't hit too hard - remember this is the front end of the crankshaft! Hit the pin as close to the inside as possible. Mostly two or three smacks should do. It is recommendable to use this pin and no other tool like a socket extension. If the pin doesn't fit proper it means that you have to hit too much on the crankshaft to get the pulley off.

To dig down to the points housing the rubber cover has to be removed. Behind the cover you will find the points housing. 3 bolts attach the lid. Undo the lid to get access to the points. Before you undo the bolts holding the points housing you should loosen the 2 bolts holding the capacitor and the static part of the points. When these bolts are loose and the 2 7mm bolts are out you can finally take out the points housing. It will come out best when you lever it out with a screwdriver on the upper corner.

Components of points assembly

Now the cam stands free. Take out the protective cover behind the cam to check the advance weights. Both ends of the weights should not be worn out. Check if you can twist the cam up to the limiter for the weights. It needs to work without any play in the weights. Check if the cam is worn on the surface from the nylon block on the points. After some time the nylon runner may mill its way into the cam. If the cam or the weights are worn they have to be replaced. When all is ok here, just clean everything and put the cover back in.

Now you start with the points housing. Take the old points out. Always replace the points when you get that far, even when the points are only a little worn.
Check the surface of the old points. Both contacts should be worn parallel. If you find a spike on one end and a crater on the opposite side, the capacitor needs to be replaced. Due to the direction of the spike you could even detect if the capacity is too high or too low. For us this is irrelevant - wrong capacity means to replace the capacitor. In return this means that the capacitor doesn't always need to be replaced. A few times I faced the problem that a brand new capacitor was defective. This is a very unpleasant thing to happen. The just replaced part is the least you expect to be defective.

Before you start mounting anything - clean the points housing and all related parts. Usually everything is covered with a yucky layer of dirt and oil. The next step is to check if the pin that works as an axle for the points is still tightly riveted to the housing. Sometimes this pin comes loose and swivels around. You may not realize this but it makes it impossible to adjust the ignition proper. Check if you can twist or move the pin in any direction. It must not allow you to be moved in any way. If you find the pin loose, you may try to hit the back of the pin with a center punch in order to reinforce the riveted connection. Mostly this attempt fails and you need to replace the points housing - but you have nothing to loose. I would give it a try.

To assemble the points, always mount the non-moving part first. Use the correct bolt to attach it to the back plate of the housing. The bolt has a thick washer and one thin washer. If you use a different bolt or leave out the washers, the bolt will stick out to the back and catch on the advance weights. To avoid this damage, always use the correct bolt and washers!

Assemble the moving part of the points with the tension spring, put it into the plastic insulator and mount it into the points housing. The condenser is mounted in its plastic bracket and bolted onto the points housing. I always replace the bolt and the tension washer that connects the +12V from the tongue connector to the inside onto the points. This is a simple 4mm steel bolt that tends to rust. Once the surface is rusted, the bolt develops an electrical resistance. This may cause problems reaching from unwilling behavior starting the car, up to a total failure of the ignition system. This can be avoided by replacing the bolt with a stainless steel bolt and tension washer. I had this effect once on one of our own 2CVs. The car didn't start at all. The search indicated that we had +12V on the connecting tongue outside of the points housing, inside was nothing. The rust had totally insulated the metal connection. The stainless bolt avoids this problem for once and all. Even if the bolt doesn't completely insulate, the 2CV will still start and run but the performance goes down. If you use an electronic ignition system that is controlled by the points, the system might fail already.

The assembled points housing goes back into its place in the crankshaft housing. Don't forget to re-connect the wire. The next step is to adjust the dwell and the timing. TIP: To crank the engine easy, just insert the bolt that was holding the cooling fan directly into the crankshaft. Once the bolt is tight, it allows you to turn the engine very easy by hand using the 14mm wrench.

There are two ways to adjust the ignition: The static adjustment as Citroën describes it in the manuals - and the more accurate dynamic adjustment with a dwell meter and a timing light.

First the description of the static adjustment

The dwell-angle is related to the gap. So to adjust the dwell-angle, you actually set the gap between the static and the moving part of the points. Turn the engine to the position where the camshaft fully opens the points. Open bolt No. 1 (See photo) just enough to allow the static part being moved up and down. Use a feeler gauge to adjust the distance between the contacts to 0.4mm by turning the static part up or down. You can open or close the gap by twisting a screwdriver between the points housing and the adjuster nose on the points (See photo, mark No. 2).

Adjust the dwell angle with a feeler gauge

Once you have reached the correct gap, the feeler gauge must just fit in the gap - it shouldn't be loose and it shouldn't push the moving part of the points away. Tighten bolt No.1 and turn the engine to open the points from the cam on the opposite side. Check the gap in this position. The difference must be 0.05mm or less. If you find a bigger difference you have to replace the cam.

Adjust the dwell angle

The flywheel must be in the right position to adjust the timing. To find the right place, the flywheel has a 6mm hole. The corresponding hole in the crankcase is in the upper motor mount on the driver's side. Lock the position of the flywheel by engaging a 6mm pin through the hole in the crankcase into the hole in the flywheel. You can easily make this pin yourself (See diagram). Once the pin is engaged, the flywheel is locked in the 8° position before upper dead center.

Locking pin for timing adjustment; dimensions in mm

This is the exact position where the points have to open. Use a simple automotive test lamp to check the current. Connect the test lamp between the negative side of the coil (The wire that connects down to the pints housing) and ground (The alternator supplies a good ground connection). As long as the points are open, the light will be on. Once the points close, the current is bypassed through the points - the light shuts off.

This is the exact position you have to adjust. Twist the points housing in its seat to reach the position where the light can't really decide if it is on or off - the slightest touch should now turn the light on or off. To enable the points housing to me twisted in its seat, the 7mm bolts that hold the housing, must be slightly open but not loose. To turn the housing you can smack it carefully on the upper corners - preferably with a piece of wood (hammer handle) or plastic (screwdriver handle). This way you avoid damaging the aluminium casting.

Tighten all bolts when the adjustment is done. Don't forget to check again - quite often the adjustment changes a little while you tighten the bolts - and very important: Check everything on the opposite cam.
All this sounds simple but in real life with twisting the points housing, you also change the dwell again. Adjusting the dwell will change the timing. It sounds like Catch 22 but with every adjustment cycle you get closer to the correct position. Depending on your skill you have to adjust dwell and timing a few times before the setting is ok.

VERY IMPORTANT: Don't forget to remove the pin from the flywheel when you are done. If you try to start the motor with the pin still engaged, the pin will bend which makes it sometimes impossible to remove it from the crankcase!

Dynamic adjustment

The dynamic adjustment is much quicker to accomplish and also more precise than the static adjustment. When the 2CV was designed there were no timing lights available so Citroen made no mark on flywheel or crankcase. This leaves it up to you to make a mark. Block the flywheel with a 6mm pin as described above. This position represents the correct timing. Now paint a mark on the flywheel. I always use correction fluid for paper. The bottle comes with a little brush on the inside of the lid. This makes it easy to paint a line on the flywheel. Furthermore, the paint is white which makes it better visible using the timing light.

It's up to you where you apply the mark. I always set it to the left side of the starter motor (passengers side). It is important that you don't mark the flywheel opposite to the left mounting arm on the crankcase. This place is tempting since you can paint a static mark onto the crankcase. But keep in mind the once the motor runs, the advance weights kick in and move the mark to the left - hiding it behind the crankcase mounting arm. Not seeing the mark isn't really helping in your attempt to adjust the timing.

In comparing the position of the mark after a precise static adjustment with the dynamic method, I determined the position for the mark offset by one tooth to the left on the flywheel. I did this in many motors and all of them showed the same deviation.

To do the entire adjustment with the motor running, you need a suitable measuring device. You can buy a dwell meter and a timing light separate. I found a timing light with a built in tachometer and a dwell meter. The instrument isn't as precise as the professional computer test centers that modern cars need - but working on a 2CV isn't quite rocket science after all. This instrument was very helpful for me over a long period of time. If you like to purchase this convenient instrument see "2CV Accessories"

To prepare for the adjustment you have to mount the points housing horizontally. Adjust the gap to roughly 0.4mm (0.0157"). Mostly this is enough to start the motor. The motor must be running for the dynamic adjustment. If it wouldn't start so far you have to do a rough static adjustment to allow the motor to start.

The final adjustment is done with the clever instrument. The red and black clips are for the supply voltage: Red is +, black is -. The green clip is connected to the coil, picking up the interrupted signal from the points, so it must be connected parallel to the wire leading from the coil down to the points. The inductive sensor is put around a spark lead. It doesn't matter which one. The 2CV fires sparks on both sides simultaneously, so both spark leads carry the same signal.

Keep in mind that the gauge for dwell and tachometer is for 4-cylinder motors. This means that it shows only half the reading for the 2-cylinder 2CV motor. Just double all readings. The correct dwell angle is 108º - 109º. Adjust the dwell to a reading of 54,5º on the gauge. The dwell stands for the ratio between the points being closed and the points being open. This ratio is determined by the shape of the cams and theoretically remains the same over all speeds. In practice you will see the needle display a different value at a certain speed. Adjust the dwell at idle and check your adjustment at different higher speeds.

Once the dwell is correct, adjust the timing. The motor must idle with 800 Rev/Min. Check the idle speed with the built in tachometer. The 4-cylinder gauge must read 400. It is important that the speed is correct. If the motor turns faster, the dynamic timing advancement will kick in. At 1500 Rev/Min the advance weights are already at their maximum position, which makes it impossible to adjust the timing correct. Adjust the speed on the carburetor. Turn the adjustment screw for idle speed outwards. If the motor is too slow you may use the choke to increase the speed to 800 Rev/Min.
When the timing is set correct the white mark on the flywheel should show one tooth left from the theoretical static position.

If the cams are worn uneven or if the front of the camshaft is bent, you will see two marks in the flash of the timing light. A distance of 3º - equal to one tooth can still be tolerated. In this case adjust the center between the marks to the correct position. When the distance between the marks is bigger than 3º check and replace the cams if necessary.

Check the dwell as it may have been changed again. If so do the dwell and timing adjustment again until both are correct. Tighten both bolts holding the points housing and the bolt that secures the points when both adjustments are satisfying. Finally check again if something changed from tightening.

IMPORTANT: As long as the motor runs during the adjustments it operates without cooling - the fan is missing! An air-cooled motor without fan and no cooling air from driving can easily overheat and be damaged. Citroën stated that the motor might not be operated without cooling for longer than 10 minutes. I think this time is way too long. The adjustment should be done in 2-3 minutes. Once the adjustment is done shout the motor off immediately!

When all was adjusted and checked it is time to re-assemble everything. Install the lid of the points housing with the rubber gasket in place. Cover everything with the rubber protector. Use grease on the 5mm bolts holding the protector. Before you mount the fan pulley check the condition of the fan belt. It shouldn't show too many cracks. Than check the oil cooler. The cooling fins must be dry, clean and undamaged.
Put the fan belt into its groove on the fan pulley and mount the pulley on the camshaft. Tighten the bolt in the fan pulley. To block the flywheel use a screwdriver in the gear - like for the disassembly before.

Finally mount the cooling fan grill - use grease on the 7mm bolts.

Now lean back and relax - you are done.