Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Bosch ignition coil for a 1995 Plus 8

Just had a look under the bonnet of my mid 80`s Mog and there are two wires connected as the coil + which would seem to indicate that there may be a ballast resistor in the circuit. I could not see a ballast resistor similar to those I have in times past, however I guess it could be built into the base block onto which the coil is mounted..?

No sign of a radio suppression capacitor similar to the one L. posted, but in my Haynes manual covering the Rover SD1 V8 from 76-87, there is a wiring diagram on page 220 the wiring diagram for V8 S models identifies item 102 as being a ballast resistor 103 being the ign coil, and 105 alongside being identified as a radio capacitor... Might be best to draw your own conclusions.

As RichardV6 determines the correct coil to operate with a Ballast resistor is 9 volts, then I have every confidence that is what it will be... as opposed to the circa 6 volts I suggested it might be, I just remembered it was a lower voltage coil... Thanks Richard.

My mid 80`s +8 has no EFI and has an alloy bodied Lucas coil with a white top....

L. I don`t quite understand the pic of the capacitor/condenser these are designed to reduce spikes on circuits with fluctuating voltages by flattening out the peaks in a voltage graph measured over short periods of time as in the switching such as an ign a coil on and off in rapid succession to fire the spark plugs, which is an entirely different function from that of a ballast resistor that is designed to drop the voltage arriving at the ign coil..

While my Mog has no visible capacitor visible alongside the coil, that the Mog was rebuilt it may have been discarded at that time.... I have never tried to listen to the radio while driving, though it does not suffer any interference from the pulsing of the ign coil or plugs, though i suspect while driving the radio would be difficult to hear over the sound of my Mog`s somewhat untamed exhaust note... (-:

Fun stuff! I miss such dialogues. I hope some others than we three find it interesting. There is a stark difference between automobile people. Some rare professionals are like you Luddite, always searching for understanding. And while I admit I have come a LONG way towards your mindset, my GoMoG Help Inbox has kept me largely amateur. Amateurs don't care about "understanding". They want a quick fix and that will get their Morgans back on the road..everything else is wasted time.

I cannot bring myself to experiment with their Morgans, only mine. If I find a sure thing fix, who am I to tell them to try anything else?!! Experience is smarter than the best theory. For example, it is not merely the part, (in this case our thingie versus a ballast resistor, but HOW it fails. If the cheaper little thingies (1 pound) fails in such a way that is undetectable and that constantly (after 30 years) causes a need to replace 500 pounds of ignition parts unnecessarily, another part is preferable, namely a ballast resistor.

I once bought, online, a Mallory internally ballast resisted coil. I figured I was saving a part and making the car less complicated (my primary Morgan goal). My understanding of such things was low. Until my arm brushed against the coil after a brief drive and a burned a section of my arm skin at the elbow off. I still have a scar that excites interest. I called and was told by Mallory, that they do not recommend them!I learned that external ballast resistors are the safest way, for both you and your pre-1995 Morgan ignition system, to go. In any event, by the time an amateur or most professionals find that the thingie (which rusts only on its unseen side) is the cause, they are asking me for recommendations for distributors, amplifiers and yet another coil. At that stage, I am not going to ask whether they 'want to experiment" with stuff I am not absolutely sure of. with someone else's money (wryly) Sheally taught me that. He was more a fixit than a theory guy too.


Yes, I know. At the time, namely 1984-1986, there were two main stream Plus 8s offered, optional EFI (for a premium on the cost), or Carb. Earlier ignition diagrams show a ballast resistor and later diagrams show nothing..which is decidedly wrong. However, there was also a different Swiss variant and the Overseas stuff. Oddly, though the USA ordered only the more expensive EFIs, they swapped out the EFI systems on arrival (except for 10 units to CANTAB) which sounds bizarre. However, for the early part of the period, you could not have R&P steering with ordering EFI.


Neither do I. But I am solution oriented and you always look for understanding. So I am more patient and reply heavily on experience. I strongly suspect it has something to do with the coil you are using. I will try to track the specs on yours down. I am interested.

As I use the best system I (and famous others) have found so far for our cars, the now discontinued Mallory Unilite (a Holly marketing move) that gives different parts #s for EFI and carb for the same LR year. I corresponded with their engineers, UK and US, for a long time. Here is their posted recommended set up.

L.

P.S,. Did you know USA ignition systems (back then) put out a tach signal that British tachometers and ECUs cannot decipher..causing both not to work.

L, as ever I admit to being easily confused and like to keep things simple to aid my understanding.... I do not understand the need for an internally ballasted coil if one such exists, my logic would expect the coil primary windings to be suited to the applied + terminal voltage.. On the other hand I have seen coils that had the ballast resistor mounted on the + terminal input connections on UK cars other than Morgans.

Generalising...The coil being made up of two internal windings, the primary connected to the + terminal and switched on and off by the distributor. The OFF switching action of the primary coil within the distributor induces the secondary winding to create a high voltage peak which is fed to the distributor HT input and from there distributed to the appropriate spark plug

Your diagram also confuses me a tad as it displays the ign switch as having one wire from it to the coil + whereas on my car and no doubt others, the ign switch will have two wires feeding the + coil terminal in order to switch the ballast resistor in and out of circuit as required... The ballast resistor out of circuit when the ign switch is held against the spring in the START position, and after the engine fires up and running the ign key released to allow it to spring back to the RUN (ign on) position at which time the ballast resistor is then in circuit with the coil.

Sorry to read that you burned yourself against the can of the coil.... It is normal for an ign coil to run hot if the ign is left on for a period of time without the engine running, as it is not being cooled by air flow past it, as would be the case in normal running.

Another cause of an ign coil running very hot would be if it is a 9 volt coil (thanks Richard) that is being supplied with 12or more volts constantly, when it should be supplied with 9 volts THROUGH a ballast resistor AFTER the engine has been initially fired up and now with the ign key in the RUN position..

As for EFI Morgans, I suspect there could be variations of triggering from the coil/distributor to not only provide information to operate the rev counter, but also related to firing the EFI... though have paid no attention to any of that over the years... More than happy to have a couple of carbs and a relatively simple ignition set up, all be it with an electronic dizzy as fitted standard to my Mog, but one which could be replaced with an old style dizzy containing points and internal condenser, and a simple ballast or non ballast coil to suit... The condenser/capacitor in the points type of dizzy was primarily there to extend the life of the points by providing a quenching effect across the face of the points as they opened and broke (switched off) the primary circuit within the coil, when the condenser failed the contact faces of the points burned up and created miss firing of the coil.

THE BALLAST COIL CIRCUIT WAS ONLY INTRODUCED TO AID INITIAL COLD STARTS IN DIFFICULT SITUATIONS. and served no other purpose that I know of... BUT... as always more than happy to be corrected where my thinking might be wrong...Richard.. ? (-:

My Mogs system is to the best of my knowledge as originally fitted to it in the mid 80`s when it was built by the MMC. the only failure to date was on the central HT sprung loaded carbon brush within the dizzy cap causing burning on the rotor arm centre point and misfiring... a replacement cap sorted that issue out..

Here is a Lucas tutorial on the original mechanical points style ignition system, which gives a good explanation of the electrical principles of traditional coil based ignition systems.

http://www.da7c.co.uk/History%20Section/LUCAS%20ACHIVE/lucas%20coil%20course%203.pdf


Luddite, I think your explanation is entirely accurate. My reading of the Unilite wiring diagram above is that the 12V ignition switch supplies 12V to the ballast resistor whenever the ignition switch is in the ON position. This would result in maybe 6-9V being applied to the coil, depending on ballast resistor value. If you move the ignition switch to the sprung START position then 12V is applied directly to the coil (and the starter solenoid) thus ensuring that 12V is briefly applied to the + terminal of the coil until the ignition switch is released from the START position and returned to the ON position. The diagram, like so many auto-wiring diagrams is not very clear to my mind.

Generally, there is 3 to 4A of DC current going through the coil if the ignition is on. So as power is I*I*R then the coil will act as heater dissipating 20 to 50 W depending on the coil resistance (1.5 ohms approx if you do have an ballast resistor installed or 3 ohms approx if you don't). So the coil will get hot. But there is also the effect of the current in the coil being turned on and off by the points or the electronic ignition - I'm not sure how much this affects the power dissipated in the coil as AC currents flow into and out of the magnetic fields in the coil. That probably makes the coil hotter in normal use - are some coils oil filled now to help cooling?

If you choose to use a coil that is intended to have a series ballast resistor without the ballast resistor (ie directly connect the + connector on the coil to 12V, then twice the intended current will flow through the coil. In that case (as power is proportional to the square of the current but linearly proportional to the resistance,) then you will increase the power dissipated in the coil by 2 - and this is why the coil is more likely to burn out in such circumstances. Again this is a DC argument, not quite sure whether it is made worse if you consider the changing ignition current.

At times, I have run my 4/4 Ford crossflow with with conventional points - well, actually an optical points sensor but essentially the same thing, or the full Accuspark electronic ignition, with or without a ballast resistor. In all cases it worked fine, (except when I wired it up wrong) provided I used a ballast resistor with a coil intended for a ballast resistor (1.5 ohm coil approx) or did not use a ballast resistor and used a coil (3 ohm) intended for use without a ballast resistor.

I imagine once you get rid of the mechanical distributor (as in a modern car) and use a sensor on the crankshaft and have a bunch of electronics and computers driving separate ignition coils for each spark plug as in a modern car, the amps and ohms numbers quoted above go completely out of the window. I don't understand modern cars at all I'm afraid so can't really comment.

SCX358G aka Dave, Thanks for taking the time to add to this thread.

In relation to your question.... I suspect many if not all old style metal can ign coils are likely to be oil filled, the oil acting as an insulator.

I only learned of the oil filling when my then 70`s British Leyland Mini would misfire only on left hand bends...??? If the steering wheel was jerked to the right when negotiating a left hand bend the engine fired as normal for a few seconds and misfire when again when the steering was turned back as necessary to negotiate the bend...

It took a bit of head scratching to resolve the issue.... On those old Mini`s the coil was mounted horizontally across the front of the transverse engine, i.e. across the front of the car from left to right...It was noted that the Lucas coil was damp with oil, which was found to be leaking out of the coil, where the alloy can was crimped around the insulated termination cap....

It would seem that in LH corners the then reduced amount of oil within the coil would, under the influence of induced G forces the oil would move within the coil can to a situation where it exposed an element of the windings within to spark internally to the then temporarily exposed internal side of the coils aluminium can, and thus causing the intermittent misfire... ?

As ever, claiming zero expertise and just thinking in type...

Back home! Forgive me for returning to this subject. But I fear that the information left as it was could lead to significant sadness for the Plus 8 crowd (mid-1980s to 2000 (or 1996 for the
USA). I have a soft spot for them.


I have never found you confused on such things Luddite, not in the last 25 years!) Yes these coils exist aplenty, at least in their advertising. A simple google will solve that for you. 🙂 Try it.
However I referred specifically to the Mallory Red Top coil (advertised as internally ballast resisted) in contrast with their regular Tan Top. As noted, I found it became too hot for safety and I switched
back to the Tan and a standard ballast resistor I have not gone near such things since.

This seems to be a case where my experience and theory do not match..but remember, in this area, my knowledge is limited to Rover/LR and Morgan V8s.

Rover/LR factory V8 specification came with two types of coil set ups. A 12V coil with the common ceramic ballast resistor which ended sometime in the 1980s and a later 9V coil with the
little beer can/canister/capacitor. I thank you gentlemen for guiding me to that. The literature is more or less consistent. The beer can absorbs electricity and then releases it. Therefore it produces
a better spark all things being equal. However, That being said Lucas distributors are all substandard. Kevin Vernon and I, along with all others though from what Kevin Vernon and I saw it a degraded
spark compared to Mallory. Mallory Unilites were not only more precisely timed but a stronger spark as well. The Mallory uses at 12V and ceramic ballast resistor. The Mallory diagram I posted above
as can be confirmed by the 100s who use it. Remove the effect of the ballast resistor and the coil gets super hot and stalls the car in 15-20 minutes, burning the coil and so on. The beer can failure
does the same to the 9V system.

At the outset, Rover/LR were worried about the beer can and the consequences of its failure. Les Hamill, the tuner/designer/writer of note, states that they originally recommended that the thingies be
changed at every annual spark plug replacement. That is confirmed by early shop Rover Manuals. But they later changed that advisory to having the thing merely checked regularly as the signs of its
failing appear on the underside, not its visible side. But in the experiences I have seen my experience by the time one notices they are going your entire ignition, coil/amplifier/distributor innards are
gone as well. At the very least, that causes a bad day..but generally it starts a much longer saga. Of course, the beer can +8s can switch to the earlier 12V system. That worked for all Plus 8s made
from between 1968 to the mid 1980s. And ceramic ballast resistors do not fail the in the same way as the beer cans, if they fail at all. BTW, I once accidentally ran my UK mog with the bonnet stay
loose allowing it to cross the ballast resistor terminals. Ran for 15 minutes and stalled, coil (a regular one) burning hot. Burned out the Mallory internal photo optic unit as well ( 2 minutes to swap in
the spare).


Ot os not my ndiagram. It is Mallory's. I have yet to find, in Rover or Morgan diagrams, two wires from the ignition switch to the coil. You may be mistaking the way these ballast resistors work. Or are
you confusing the negative terminal to tach (and ECU)? Gomog and the internet is full of wiring diagrams for your to confirm. A ballast resistor permanently reduces current and dissipates it through
heat-resistant ceramic. The beer can absorbs electricity for a milli-moment then releases it or so is my understanding. The Mallory diagram works for me and 1000s of others with our engines.

BTW. here is the story on your system. https://www.nonlintec.com/sprite/cap_failure/ Another sign of pending failure is the car overheats caused by the hyper-heated coil adjacent to it The MMC
diagrams and the LR/Rover L-Jet and Hitachi Hotwire diagrams reflect the Mallory wiring. NAMELY, one wire from the coil, one to the tach (and then on to the ECU if there is one) and the earth. But
by your car, they were incorrect.


That is what is happening when the beer can fail.


Actually, the ignition system was built by Rover or LR at that period. And yes. ! I have been there as well. (pow, sputter, bang). I carried and had occasion to use a replacement cap&rotor. This
experience is common to Lucas dizzies. It has never happened since I swapped distributors. Lucky I guess. I appreciate you desire to continue with original equipment (actually our cars were made
during a transition period both ignition and engine source wise). I am a long distance mogger and cannot tolerate the vacation risks that come with some equipment. Lucas is far more complex to deal
with and less reliable than other ignition solutions. Hundreds of owners, have moved to Mallory..which is sadly been cancelled for more profitable fare since the Mallory purchase. But whatever you have,
your car is more reliable and less risky f you switch back to the earlier system, for the reasons given. Either that, or check the underside of your beer can every time you check your motor oil. Carry an
extra beer can with you. They are only 2-3 quid.


Thank you for your help, G & R.

Lorne

P.S. What did Rover/LR switch from one system to one they knew to be less reliable? Best I can figure is that the 9V and beer can is cheaper by 8 quid. 30,000 units x 8 a year.

L, I suspect any apology should be mine. I can see where my contribution may have caused confusion for others, when my foundational perspective on ignition thinking is based on old circa 70`s technology with points and condenser/capacitor mounted within the distributor, at that time the idea of introducing a coil which operated below normal battery output voltage and thus required to be fed through a ballast resistor to reduce the voltage supplied to the coil IN NORMAL RUNNING was new tec.

Now having taken a little more time in the attempt to clarify my muddling thought patterns... For me, the confusion was the mention of a ballast resistor required in an electronic system, which suggested that some aspect of the 70`s style ign system was still in use causing me to think back to basic principles..

I know nothing of Mallory systems, and in my limited experience have not come across an internally ballasted coil.

Re the wiring diagram you posted... it is of course a generic diagram, MY confusion was in relation to the ignition switch having a simple on/off function, which is not the case on the era of Morgans in question... whereas a Morgan and many other vehicles of that era, has an ignition switch having OFF/ ON /START functionality.

However the diagram is indeed applicable, in that the functionality of the ballast resistor in the circuit is identical to that of the 70`s ignition circuit I described... Just that the distributor internals are electronic and should be viewed in their own right, as a separate item, much as the ignition switch is simplified in the diagram as a simple on off switch, the distributor is in this regard an on/off switch, just that it is switching the coil on and off rapidly relative to the engine`s RPM.

The diagram also includes the other vital connection for a ballasted ignition circuit to operate correctly, and identifies that wire as "other wires connected to the coil (+) terminal if any," This wire will be the wire that supplies the coil with full battery voltage ONLY when the ignition switch is held in the START position..

Were the diagram directly Morgan related, it would show the routing and connection of that all important wire.... which COULD be fed directly from the ignition switch or any other connection which is only made live/hot when the ignition switch is held in the START position.... i.e. perhaps connected to the starter motor control solenoid SOLENOID, as can be identified on the diagram in the test card number 4, which I hope to post below..

Hopefully all that typed, the operation of this basically two function circuitry might be simplified....? The two functions being primarily to provide the strongest spark possible with a battery struggling to provide it`s usual circa 12 to 13 volts, be that due to an aged battery or even a new one, on freezing cold start conditions. The Second function being that of introducing the ballast resistor circuit to take over supplying the coil with it`s lower and designed normal operational voltage, after the ignition key is released from the START position, the ignition switch having sprung back to the ON position in normal running, thus maintaining a voltage at the coil...

Jeez A lot of words typed trying to keep things simple.... Sorry, I hope I have not further muddied the water..

I care not a jot if only three people might be reading this, if it helps any one person gain a better understanding, then that works perfectly for me...

George wrt the OP and I had his request answered (from Stateside) and the correct coil ordered all within 13 minutes, but it has rambled on for pages and days now

That's the strength of TM an honest uncomplicated answer to a straightforward request is swiftly dealt with and no additional complication unlike other sites where hot air abounds.

To be questioned about your request is rude in the extreme, none of us on here are children or on trial..

Richard, I jump in and out of TM as and when suits, thus I suppose like many, I do not either read or remember the whole thread, and am more than likely to respond to the most recent contribution, perhaps just going back a bit in the thread to remind myself of that which I might have previously typed as I do tend to ramble on a bit as being succinct might be fine for those sharp of mind, but others like me require a bit more explanation. That I forget so much does not aid my thought processes..(-:

I also thought that anyone searching under the topic heading at any future time trying to resolve an ignition problem might find it interesting to read through the thread in the hope of learning something.. While it is great to have access to a short reply that provides a quick fix, when trying to find parts for an old machine that are no longer available or difficult to come by, at which time having an understanding of the operational requirements of the system might just assist in finding alternatives, which if I remember correctly (-: cropped up in the subsequent posts.... Whatever, the main thing is that the OP`s Mog is hopefully up and running again... (-:

BTW I found no problem whatsoever in being questioned or corrected in terms of my thinking, I am often grateful to be corrected just as John V6 has been kind enough to do on occasion when I get things wrong, for me it is all just part of the learning process or should I type, re-learning process... (-:

All just part of the fun that is TM..?

George,

It's all part of the much famed TM drift with humour