Ducellier 4155 D distributor - Strip Down and Overhaul

I decided to rebuild the mechanical Ducellier 4155 distributor I had recently acquired from Paul at Pallas Autos. If someone has an ignition problem - or even a general running problem - a quick and easy response is to suggest they upgrade to "123 electronic ignition"  But that's an expensive solution and some people don't have the luxury of splashing out like that. Servicing their existing distributor might solve  - or eliminate a suspected problem.

Finished results

If you’ve read my post from 16 December 2018, you’ll have read that, when I started my restoration, I discovered that my car had the wrong distributor fitted..........

Both Ducellier and SEV-Marchal made and supplied distributors for Ds. The brand shouldn’t matter, however different models of D have different variants of distributor - and for a good reason. By virtue of an arrangement of weights and springs, they are set up to behave differently (have different advance curves/ characteristics) under engine load. For optimum engine performance it’s important to have the right one. Putting the clues together was like following the Da Vinci Code! 

DV = 'Wrong distributor not 'Da Vinci'......

Two separate tables in Operations D.210-00 and D.210-0 in Manual 814 list the appropriate distributor for each model of DS. My DX2 engine had been fitted with a Ducellier 4254D (coded DV-010A signifying it is for a DV engine). I couldn’t find a reference to a 4254D in the tables but a DV-010A was used on D Specials between 1969 and 1972 and then on DS23s (!?). 

Putting the clues together......

My 1968 DX engine should (apparently) have had either a Ducellier 4155B or a SEV-Marchal A147 distributor (both carrying the code “DX-05b” signifying they are for a DX engine). The tables also showed that, at a push, a Ducellier 4253B or SEV-Marchal A222 (both coded DX-05i and as fitted to DSuper 5s) could be used. As I say, the right SEV-Marchal distributor would do the same job, but as all the other equipment on my car was Ducellier brand, I was keen to find a 4155B. So I started hunting…….

During my online research “123 electronic Ignition” kept cropping up as an alternative to a conventional distributor. As it is electronic, via a small selector hidden behind a hex nut, 123 can be set up to replicate the different advance characteristics of different DS distributors - including the DX-05. Instructions with the 123 include a look-up table to tell you which indicator position corresponds to what DS engine and what DS advance curve - so those tables above are very handy to have.

123 can replicate different DS advance curves. 

123 is said to give more consistent firing and overall performance - in terms of starting and smooth, consistent running. However at about £275, 123 wasn’t cheap and I resolved to stick with a mechanical distributor - partly for originality, but mostly because of cost! I reasoned that with many DS owners making the switch to 123, and with so many DS21s and DSuper5s around, it shouldn’t be too hard to find an unwanted DX-05 distributor. Should it?

I contacted the range of DS parts suppliers that seemed to have cropped up while my car had been off the road - Pallas Auto, DS Workshop, Citroen Classics and Peacock Engineering  - but none of them could help. Pallas Auto had a good hard search for me and sourced a distributor marked “DX-05i” from a 2347cc DX4 engine - but confusingly that turned out to be a 4259B distributor so I let it pass - sure a DX-05b would turn up eventually. 

At about this time in 2014 I went to visit Toni Papa and his DS in London. We discussed 123. He’d fitted it and was very happy with it. Was his old distributor going begging by any chance? Sorry, no: he also carried his old mechanical distributor around in his boot as an emergency spare if the 123 failed (they rarely do you know....). Anyway, perhaps this was why I was having trouble finding an old DX-05b? At the time (and with an engine rebuild yet to happen), a distributor wasn’t a priority and I dropped the search.

By 2018 I was near to completing my engine rebuild. I had mellowed as well as aged and gave in: I bought 123 electronic ignition at Citromobile as it was too cheap to resist. I took comfort from the fact that it could at least be set up to correctly mimic a DX05b. So the deed was done.

However when it came to a first test start of my engine I actually re-fitted my old (wrong) DV-05 distributor! (You can read about that in my 16 December 2018 post). I am saving the fitting of the 123 until the engine is back in the car and I fit the new wiring loom. At that point I had planned to keep my DV-010 distributor in the boot as an emergency spare if the 123 ever failed. I’d still have preferred a DX-05 as a spare though……

In one of those weird twists, in June 2019 someone on one of the Facebook DS groups put out a plea for a distributor for a DSuper5. Paul at Pallas Auto offered a DX-05b! Luckily for me it turned out the searcher was actually after a DY010A distributor for either a D Special (or maybe a five geared D Special?). Anyway, the key point being that both of those are 1985cc engined cars. As such, the DX-05 was not wanted.

I contacted Paul. Yes - not only was it a Dx-05b, it was a Ducellier! And yes - it was still available. A deal was struck. I still planned to use the 123 distributor I had eventually bought but at last I now had an appropriate back up distributor to carry in the boot. I picked it up from Paul at the D rally in July. It is indeed marked DX-05b and so for a 1968 DX engined DS.

The elusive "DX-05b".........

But, oddly, the model number is 4155D (not 4155B). I couldn't find any reference to a 4155D distributor in the tables in the 814 Manual - but neither could I find evidence of a 4155B on the internet . Well not yet anyway. I'm concluding the manual has a typo and suspect they got muddled because of the 'b' of 'DX05'.

It looked as grubby and unloved as any other distributor you see. Although it's only for use as a back-up, I decided to strip and clean it.....

The procedure isn't covered in either volume of manual 814, but there are some pretty basic (and incomplete) instructions at Operation DX.211-3 in Manual 518 from 1966. Two procedures cover the Ducellier and then the SEV-Marchal distributors of the day and are at least helpful reference.

With the distributor cap removed and rotor arm off, the first job was to remove the square-headed 'primary terminal' screw from inside the body. 

Black wire from contact breakers is connected to the primary terminal

This primary terminal is insulated from the outer casing of the distributor by plastic spacers and has a surprising number of nuts and washers on it. These included the broken ring terminal end of a wire. I suspect this may have been an earthing lead? I'm not convinced all the others are needed.

Primary terminal screw - with insulators, washers and nuts

With the primary terminal out of the way, the carrying plate - suspended over the springs and weights and carrying the contact breakers - could be removed. This is held in place by three screws.......

The carrying plate is suspended within the distributor

......two of which also carry the black spring clips for the distributor cap. And in the case of one of those screws, also the condenser.

Screw secures carrying plate and also clip

Both parts of the contact breakers were removed, allowing access to the cam follower and spring.   (I haven't a clue what the cam follower does. It is spring loaded and slides in a track in the carrying plate. I just don't know why.) I gently held this back with a screwdriver blade to enable me to slip the carrying plate over the drive shaft.

Holding back the cam follower with a screwdriver tip

Lifting out the carrying plate then revealed the cam beneath, complete with weights and springs - the heart of the distributor.

Cam with weights and springs on the rotor.

Turning to the other end of the distributor, I prepared to remove the roll pin holding the drive head in place. 

The drive head

The drive head has a 'big half' and a 'small half' and engages in the drive socket inside the distributor drive tower. That, in turn, is driven by the rotation of the camshaft, which is driven by a chain from the crankshaft.

To maintain the correct relationship (firing order and point) between crankshaft rotation and the rotor on the top of the distributor, it's important that the drive head on the bottom of the distributor spindle..........

Drive head. Note "big half" at the bottom

........is correctly aligned to the notch on the top of the cam.....

.... as that then sets the position of the rotor arm itself.

Locating lug inside the rotor arm

Making a note of their relative positions, I drifted out the roll pin.

The drive head is held on the spindle by a roll pin

Cradling the upturned distributor over a vice I then drifted out the drive spindle to free the drive head - remembering to catch the assembly before it fell to the ground!

Freeing the drive head from the drive spindle

On the outside of the body was the drive head, together with two thin shim washers sandwiching a fibre  'celeron' washer. There was a similar three washer arrangement inside the body underneath the cam plate.

Spindle and washer arrangement

With the spindle freed from the distributor body I could now have a good look at the weight and spring arrangement. I was surprised to notice that the two springs were completely different sizes.

Weights and springs on the distributor cam

Some quick Googling revealed that his was nothing to be alarmed about and that it was quite acceptable to have springs of different sizes on the same cam. I'm guessing that using different combinations of springs is one of the main ways to give different models different behavioural characteristics. I unhooked the springs.

Note different sized springs

I removed the circlips that hold the weight guides in place on the cam and removed the screw on the tip of the spindle. This is meant to be covered with a felt pad which is kept soaked in oil. This lubricates the cam on the spindle (and possibly the spindle in the distributor body itself?). Both my distributors lack this felt pad but it won't be hard to make something up. I separated the cam from the drive spindle. The cam has the four eccentrics which, when the cam rotates, open and close the contact breakers.

To the left: drive spindle with weights. To the right: the cam

I removed the circlips that held the the weights to the drive spindle.

Weights and cams separated 

The many bits were then thoroughly cleaned and, while we were away on holiday, I had the body vapour blasted for good measure.

Under the rotor on the spindle was a recessed area that seemed to be packed with something other than dirt and with the consistency of clay. Was it graphite paste to reduce friction? Was in a disintegrated rubber seal?I didn't know so left (what was left of) it alone.

Black 'clay' under the rotor

I noticed that one of the spring posts seemed to be bent from the perpendicular. This would be putting the spring under more tension. I wasn't sure whether this was some kind of micro-adjustment from when the distributor was assembled and calibrated so left that alone too.

Spring post on the right seems bent?

Reassembly is the reverse of disassembly, but I will go through it anyway.

The weights were relocated on their pivots. 

Refitting a weight

Manual 518 says to 'lightly oil' parts on reassembly. By and large I took this advice - only using light grease at a couple of points.

The 'rollers' that locate the weights in the cam were refitted........

I used a little light grease on the outer circumference to aid smooth movement in the slots of the cam, and the cam was then duly refitted on the end of the lubricated spindle.

The cam was located overs the rollers of the weights

Circlips were replaced and the screw holding the cam to the spindle was tightened. I checked for free movement of the cam and excessive float.

The cam was screwed onto the drive spindle

This is perhaps a good point to give a basic explanation of how a mechanical distributor works. For each cylinder/ piston in the firing sequence, that ignition point is triggered by the rotation of the rotor arm in the distributor cap. The compressed fuel/ air mix in your engine takes time to combust and ignition needs to start and complete at an optimum point of the piston stroke to generate optimum power. As engine speed increases, the pistons are of course moving faster. Without the advance mechanism in the distributor, this would mean that the piston had passed it's optimum compression point by the time the fuel eventually combusted - leading to reduced power......

As you can see in the photo above, the rotor arm sits on a cam which is only indirectly connected to the rotor: the rotor has two weighted 'arms' fitted to it, which locate into curved slots in the cam. As the drive spindle and rotor rotate faster, the inertial force on the weights overcomes the countering centripetal force provided by the springs on the cam and the weights lever outwards rotating the cam with them - slightly.  The rotor arm perched on top is similarly rotated a little - meaning that the ignition is 'advanced' relative to the movement of the drive spindle, camshaft, crankshaft and of course pistons: ignition takes place a little sooner to give the fuel time to still combust at the optimum point of compression.

The springs are not connected, but here is a quick video demonstration of the movement of the weights and rotor arm:

VIDEO: demonstration of distributor advance

I'm guessing that different lengths of grooves in the cam would allow the rotor to rotates by differing numbers of degrees, and that different spring tensions would determine the engine revs at which the weights began to move. Is that how it works?

Anyway, back to the rebuild. The springs were added. There were a little tricky to locate. I put a little light grease on the underside of the rotor where the strange 'clay' packing was. With the three washer combo then in place and the spindle oiled, it was refitted in the distributor body.

Rotor assembly back in the distributor body

At the bottom end, the three washers were refitted and the drive head replaced with the roll pin. 

With the position of the cam on the rotor now set by the weights and springs, I was careful to orientate the drive head on the spindle to it's correct position relative to the slot in the rotor.

There was a little more float in the spindle than I was happy with and I should really have experimented with adding an extra shim washer to the sets of three - except I didn't have any big enough to go over the shaft. The drive head is easy to remove so it's something I can come back to.

On the carrying plate, the cam follower (what DOES that do??) was refitted in it's guide and against it's spring. I used a little light grease as it seemed to have been greased previously.

Refitting the cam follower......

The carrying plate was slipped over the end of the cam. It was easy to work out which way round it went as it will only be screwed in place at three points.

Carrying plate relocated. The round hole is for the 'primary terminal'.

I had a dig around and turned up a new Lucas condenser and new set of Bosch contact breakers. 

The breakers were refitted.

Fitting the moving contact breaker

The primary terminal and all the nuts and washers were next. The square-headed screw and first insulator go inside the shell of the distributor. 

The primary terminal

The round plastic washer and the rest go outside of the body. The contact breaker wire was fixed to the primary terminal.

The condenser and distributor cap clips were refitted - in the process serving to secure the carrying plate over the cam. I was careful to align the plate at it's three fixing points before I tightened the screws as I was wary of cross-threading the screws in the soft aluminium body.

I took a moment out to compare the rebuilt distributor to the one I had used to test run my engine. It looked a whole lot better!

Compare and contrast

I also managed to dig out a new Ducellier distributor cap and rotor arm.

So what's left to do? I will cut a felt oiling pad for under the rotor arm. I may investigate a shim washer to adjust the float in the drive shaft. I may make up an earth lead for the primary terminal. I need to set the plug gap. In fact before I think about carrying it around in the boot as a spare, I will need to fit it and test it under driving conditions. 

The old and the new....