Rotor arm, wierd happenings man!

[Red 6]

After about 15 miles from rebuild my 6 started to run rough, it felt like bad petrol or a misfire on a coulple of cylinders orblocked injectors.

 

It then stopped altogether and would not re start.

 

I put a spark indicator on number 1 and there was a spark.

 

I put a timing light also on number 1 and turned the engine over.

 

Each flash occured at a different place on the front pulley.

 

I checked the plugs for fouling, he points for shorting and the coil. All worked well.

 

I changed the brand new rotor arm for an old one and hey presto it worked better than ever.

 

There is nothing to show any problem with the rotor arm it looks perfect and it is new.

 

After a few miles i re fitted the "new" rotor arm and the problem returned.

 

This has never happened to me before has anyone else had this problem?

 

BTW it was a Lucas part.

[Guest kp1]

Yep, I've had a similar problem.  Eventually leads to no spark at all to any of the plugs and therefore will not start!  I was lead to believe the problem lay in the distributor spindle being just too wide (or the rotor arm just too small), so that when you push it on, you create a hair line crack in the rotor arm which sends the current intermittently to earth through spindle.  I always carry a couple of spare rotor arms just in case, although it has not happenned for a year or so now.

[Bob Stubbs]

Haven't had the problem but a solution was recommended to me.

 

Check and see if the rivet attaching the brass connector (that contacts the plug leads inside the dizzy) is brass or plastic.  Seemingly if brass/metal they have a tendency to short through to the metal contact that secures it to the rotor spindle.

 

Fit the ones with the plastic rivet and apparently the problems sorted.  Revington have them as doubtless do some other suppliers.  Small detail but useful to know.

[paul7]

I had a simular problem a couple of years ago, car ran fine for 2/3 months of shortish journeys on a new rotor arm. took it on a good long run and it kept cutting out. I thought it was the lucas pump (Rare day the sun was shinning) if i left it for 10/15 mins it would restart. After several stops it got worse until it finally gave up and wouldnt start. I called out the AA and told him not to mess, its the fuel pump just take me home. Smart A*s* took one look at the rotor arm a told me its the wrong one. I swopped it for an old one i had in the boot, car started first time. the new one was a fraction shorter in reach which must have failed when temperature got up ? It was bought new from a `specialist` but cant remember which one

[Guest andythompson]

I had my engine miss a bit then die. Traced to new lucas rotor arm. Fitted a scabby old one from the depths of my toolbox and no problems since.

 

Moral: Lucas "new parts" are not made to the same quality as the old stuff. This is a real dilemma when servicing cars for reliablilty. Any answers??? I try to keep old servicecable bits rather than replace them for the sake of it.

 

Does anyone supply good new parts anymore!!!!!

[Guest povey]

Hi,

 

Had this and found the bolt that secures the distributer came loose.

 

The distributer gradually came loose.

 

Misfires, ruff running and eventually no spark to the plugs.

 

Simple fix reseat distributer and set static timing.

 

Mike

[marvmul]

A lot of people seems to have trouble with new rotor arms

(Lucas, DRB106C). In 3 months I had twice a rotor arm that failed on my TR6. I've made a long trip this week-end and took 3 spare rotors with me, 2 of them were new and I had a third one made up from a 4 cyl rotor by rivetting an extension on it. After 250 km, all of the rotors were used up. When I refitted a defective rotor, I could drive 1 km or less before coming to a halt again. Fitting a spare coil made no difference. At a moment I thougt of calling a recovery truck. My TR6 has a Lumenition electronic ignition since 12 years and in the end I thought that this could have something to do with it. Luckily I had a spare distributor(TR4 type) for my TR3 with me : the points and condensor can be fitted in a TR6 distributor and thus I could return to a standard ignition, without the Lumenition.

The problem was solved : I got home without any problem, using a 'defective' rotor.

I think  their is a problem with my Lumenition ignition because I needed 4 rotors during the trip. A lot of people have fitted an electronic ignition and they won't need so many rotors.

There must definitely be a problem with the new Lucas rotors but I wonder if people who have a standard ignition on their cars have problems with these rotors, or has it something to do with the electronic conversions (stronger sparks)?

[Andy Moltu]

There are pleanty of **** rotor arms around.

It's generally worth changing the dizzy cap at the same time as a rotor arm so that the new rotor arm doesn't hit the deposits on the old cap.

[jean]

A few years ago I fitted a new Lucas rotor arm to my 6. After 300 miles the engine stopped in the middle of a busy crossing point. Fortunately I had the old rotor with me and after changing the car started straight away. Next day I checked the rotor and noticed a hair crack at the height of the small spring. As Andy said ****/10    

Jean

p.s. If you have a Lumenition constant energy system it's wise to put the appropriate Lumenition coil. Lumenitions sells different systems, looking all alike, some require a special constant energy coil  ???

jean

[Tony.C]

I had a similar rotor arm problem last year - spent hours searching for the fault, even stripped off the electronic ignition at one stage (now re-enstated). On the rotor arm the rivet holding the contact was loose.

Solution was relatively simple - mixed and applied a small amount of araldite to the splined rivet, warmed the rotor arm with a hot air gun for a few minutes. When the contact was immovable - refitted the rotor arm and have had it installed / running ever since without problem.

Didn't see much point in buying another one and potentially finding the identical problem again.!

Regards

Tony. C

[jonlar]

This problem seems to be accentuated with electronic ignition systems - could this be because of the fatter higher voltage spark being able to jump bigger gaps - logically it should take the shortest route to earth, but funny things happen with carbon or metallic dust being present.

 

The first electronic ignition kit I used was a Piranha system which I fitted to my 1972 Ford Capri V4 2.0L, much improved starting, running and performance.   As a matter of interest I disconnected the king HT lead, took it to the suspension bolt, inserted and held it in place with some clear plastic tubing, I got the gap to just over 3/8" (approx 1cm) before the spark stopped jumping the gap.

[jean]

It could be, but as far as I see Electronic Ignition only triggers the spark, I do not see any impact in the strength of the spark. If something is influencing the spark it could be the Sports/High power coils. These could deliver an electric tension that is beyond the isolating capability of  badly manufactured rotor arm or dizzy cover  ???  As said damp or dust inside will magnify the problem.

Up to now I only heard about rotor arm crack problems, in the case the electric load is rerouted straight into the dizzy shaft

Jean

[jonlar]

It could be, but as far as I see Electronic Ignition only triggers the spark, I do not see any impact in the strength of the spark. If something is influencing the spark it could be the Sports/High power coils. These could deliver an electric tension that is beyond the isolating capability of  badly manufactured rotor arm or dizzy cover  ???  As said damp or dust inside will magnify the problem.

Up to now I only heard about rotor arm crack problems, in the case the electric load is rerouted straight into the dizzy shaft

Sorry Jean, but I have to correct you on this one!   The optical part of the electronic ignition replaces the CB/points. which wear and burn causing timing (and the charge to the condenser) to suffer.   It is the condenser (electrical capacitor) which alternately charges and discharges through the coil to the distributor lead.   The electronic part of the module applies a much more powerful charge through the coil, with a typical standard coil output voltage is in the region of 25-30KV (points and condenser give 10KV - if you're lucky)  (a "sports" or high performance coil can give 30-35KV) with a re-charge time in the region of 20 micro-seconds, which is faster and more constant than a condenser.   I remember seeing a "health" warning on some electronic systems saying they can cause death or serious injury!

[jean]

You must be right  Jon, I never looked into the technical part of the electronic ignition system. What made me thinking is that the tiny little wires coming out of the module can't deliver much electric tension to the coil. Their only advantage could be speed and timing. Further I read that most electronic systems work in a constant energy mode, whatever they mean by that. So I understood that the coil is under permanent power and not loaded by a condenser, and that the electronic module is steering the discharge. For this reason the coil is switched off as soon as the module does not receive a feedback that the engine is turning. But maybe my way of thinking is too simple and I will have to look deeper into it. Thanks for the explanation        

Jean

[tim_trinda]

The optical part of the electronic ignition replaces the CB/points. which wear and burn causing timing (and the charge to the condenser) to suffer.   It is the condenser (electrical capacitor) which alternately charges and discharges through the coil to the distributor lead.

 

Jon

Sorry, I don't think that is right.

 

The purpose of the CB(points) is to turn the current on and off in the primary winding of the coil by connecting it ground. When the CB are closed current flows through the primary winding producing a magnetic field for energy storage. At the ignition point the CB opens, interrupts the current flow, the magnetic field collapses and the high voltage required for ignition is induced in the secondary winding. This voltage is fed to the distributor and then on to the appropriate spark plug. The purpose of the condenser is to reduce the amount of sparking, and consequent wear, which occurs as the CB open and close to switch the current in the coil.  

 

There used to be ignition systems around years ago which did use capacitors to store energy, and were discharged through the primary winding of the coil to produce the spark. These systems were called Capacitor Discharge Ignition - not surprisingly!

 

===========

Tim

[jonlar]

Tim and Jean, this is getting interesting, if the condenser was just to reduce the amount of sparking, the system would work without one, but go through points very quickly - which isn't the case, it doesn't work - I thought the condenser charged and discharged back through the coil as the points open, .   Can anyone else come in and assist on this one?   I can see what you're saying Tim about the points being closed, earthing the primary coil etc..   In any case, what I can say for sure, is that when cranking over the voltage can drop so much that the coil puts out very low HT, but electronic modules produce the more constant and much higher HT.

[Tom Fremont]

As an electrophobe generally, I'm probably not qualified to comment, but I think the points are isolated from earth by insulating washer and can only get to ground via the lead to the condenser. If this is so it would explain why it doesn't work with the condenser removed.

 

From distant memory, theory has is that V = L x dI/dT or voltaqe = inductance x current drop with respect to time. The faster the drop the higher the voltage, with inductance a constant built into the coil, and voltage is proportional to current by this equation. Pretty ingenious invention ( 19th century? ).

[jonlar]

Thanks for your input Tom, all comments welcome!!

 

I also recall the CDI system referred to by Tim, as far as I remember though instead of using transistors to amplify the signal to the coil, these used a larger capacitor/condenser which produced a higher charge through the coil.

[rayjones]

The early electronic ignition systems used the original points and capacitor in the distributor, They generally had a couple of power transistors oscillating through a transformer, to increase  the voltage to the low tension side of the coil. The main advantage was that the trigger current going through the points was very low, and therefore did not burn the contacts, although there was still mechanical wear. You were also recommended to increase the plug gap considerably to take advantage of the better spark. I used to find that cars stayed in tune much better with this sytem than just using points, coil and capacitor. I built one from a kit and used it on my first three cars, totalling around 240,000 miles between the three of them back in the sixties and seventies, and never had a moments problem with it. You did need extra suppression though, otherwise you could pick up interfererence on the radio from the oscillator

[Guest harry dent]

I am with you on this one Red six(could be a first, he! he!)

The repro,s are rubbish and so are some of the dizzy caps.

Which one,s are better or worse I cannot tell you.Source

only original stuff but leave some for me to stock up on.

See you at the inter Red six or Thursday the 8th at The Boot

in Chipperfield.

Regards Harry TR5 nutter. ???  ???  ???

[marvmul]

Weird results!!

Did some experiments with coils and electronic versus CB (=contact breaker, standard) ignition.

As I mentioned in a former posting, my TR6 was eating rotor arms, one for every 50 mls. The problem was resolved when I removed the Lumenition el. ignintion (about 12 years old) and installed the standard ignition with contact breaker.

Today I measured dwell and maximum gap that could be jumped by the sparks (with Gunsons Flashtest : sort of scissors with 2 points that can be opened from closed to 20mm, it's inserted between a plug lead and an earth point)

 

Set ups and results :

-TR3, new Lumenition Performance Ignition with the Lumenition sports coil :  gap : 20 mm : very strong spark, dwell : 15° at tick over and 60° at about 5000 rpm : so it's not the dwell angle but the dwell time that remains about constant with this ignition : this makes sense : the energy built up in the coil depends on the time that the negative of the coil is earthed (= dwell) : so the energy of the sparks remains constant over the rev range. With contact breakers, the time for building the energy in the coil becomes shorter with higher revs, so less energy then.

-TR6, standard ignition and standard coil : max gap is 10mm at 1000/' and 8mm at 4000/'. Dwell is 30 degrees (after adjusting the contact points)

-TR, standard ignition and lucas sports coil : max gap is 11mm, about constant in the whole rev range.

-TR, old lumenition ignition (and thought to be defective) and sports coil : max gap 8.5mm and dwell is 12 mm at 1000/' and 7mm at 4000/' , fitting a standard coil made almost no difference. This is the set up that makes the rotor fail at a very fast rate. The old lumenition ignition is clearly defective, but it's a mystery to me why the rotors fail : the max. gap is 8.5 mm, about the same as with a standard ignition (the dwell is very short) and much less than with the new Lumenition on my TR3 (20mm) . Can someone shed some light on this?

[kenclaw]

Going on my knowledge it seems to me that the purpose of the the capacitor is not only to suppress the spark but as the points break the capacitor will draw current through the coil to charge it up thus the interuption of current flow will be slowed down causing a wider pulse  (longer time) which will create a fatter but lower voltage spark of higher current rather than a high voltage low current spark.

Ken.

[tim_trinda]

if the condenser was just to reduce the amount of sparking, the system would work without one, but go through points very quickly - which isn't the case, it doesn't work

Jon

I'm surprised the engine won't start without the condenser fitted (although I've never tried it!), I was under the impression the engine would run but due the large amount of sparking and subsequent erosion of the points not for very long.

 

I think the points are isolated from earth by insulating washer and can only get to ground via the lead to the condenser.

 

Tom

Only one half of the points set is insulated i.e. the half operated by the distributor cam, the other, fixed, half is screwed directly to the distributor base which is grounded through the distributor body. You can check this by removing the wire to the coil and connecting a 12V bulb between the connector on the distributor and the positive side of the battery. the lamp will light when the points are closed and go out when the points open - useful for checking the static timing too!

 

Marvmul

Your results were very interesting and food for thought when switching from points to electronic ignition. I would think that your new Lumenition electronics/coil package has been optimised to work together to produce maximum HT voltage over the rev range which will never be the case, unless you are very lucky, when the component parts are sourced from different manufacturers. Did the you make any dwell time measurements on your old Lumenition?

 

=========

Tim

[marvmul]

Tim, dwell was only 12 degrees at 1000/' and 7 degrees at 4000 /'. I wrongly wrote mm's instead of degrees in my previous post.  Something must be wrong with the old Lumenition : dwell should be much longer and the spark should be stronger. When I replaced a faulty rotor arm with this Lumenition, the engine didn't run or only a couple of minutes, a new rotor lasted an hour or two. But when I use a faulty rotorarm with the conventional ignition, the engine runs without any problem. So, only an excellent rotorarm is ok for the Lumenition, a 'faulty' rotor is still good enough for a conventional ignition, and perhaps an electronic ignition that is in good working order.

[jean]

I just don't understand that a rotor arm is faulty when it runs with a standard setup. It just does not work with the Electronic ignition. I think when fitting the electronic ignition

you will have to consider that due to the chopper thickness the rotor arm will be positioned higher than on a standard ignition.

My TR6 runs since 98 on a Lumenition set and I only had once a cracked rotor, but this was due to poor quality and probably had nothing to do with the system itself.

Jean