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MG Midget and Sprite Technical - Ignition coil and ballast

Morning :)

I am tracking down some misfiring on my engine (Reg L - 1275cc - Lumenition Optronic), and while looking under the bonnet for obvious things, I found some "liquid trace" on the HT lead connector of the ignition coil... Not 100% sure it was oil as when I cleaned it, the paper was not getting brown : was closer to WD40 style I recon. But it was not coming from another place, as when I disconnect the HT lead connector, I also fund some drips into it... Anyway, I cleaned everything and see what I get after the next ride !

In case I need to change my coil, I got a bit lost in the choice of new ones...
Lumenition say that their system is designed for 3ohms or +, and I have their coil + external ballast mounted on the car (same as this https://rimmerbros.com/Item--i-GCL132MS?gclid=EAIaIQobChMIrqe_sJHc4wIVhbTtCh3afAXpEAQYBSABEgIxL_D_BwE)
After checking the archives, I fund some people recommending simonbbc/powerspark so I emailed them for recommendation, and they indicated me this one : https://simonbbc.com/viper-dry-ignition-coil-sport-in-silver-finish/
In their mail, they say it is non-ballasted, and it shows 3ohm coil on the website...which I would interprete as a "internal ballasted coil not needing external ballast", no ?

=> Do I need a 3ohm non-ballasted coil, removing the external ballast mounted on the car ? Or something else ?

I go grab paracetamol...


CH Hamon


It doesn't matter
You can use either or, as long as the total resistance is around the 3ohms
ie-
---3ohm coil
or
---1.5ohm coil and external resistor

If you went for that Viper 3ohm dry coil you would fit it up without the external ballast

That oil sounds like the coil is starting to leak, if it's been leaking for a while and the oil level is down it can cause a missfire
William Revit

Thanks Willy ! Some information were contradicting, so I wanted someone trustworthy to double check :)

One more question... Does it mean the coil with internal resistance are the one which can bypass it for more efficient cold start, whereas the one with external can't ?
CH Hamon

Optronic then, iF you need a new coil then unless those more knowledgeable say different for the sake of a £210 kit I would stick with the matching coil.

See - https://autocar-electrical.co.uk/lumenition

https://autocar-electrical.co.uk/images/pdf/pdf_optronic/hbook-Sec-1A2-070207.pdf

https://autocar-electrical.co.uk/images/pdf/pdf_coils/MS4-Instruction-V1-4.pdf

ETA: Willy posted whilst I was compiling info.
Coil looks less cost from manufacturer unless they charge a lot for postage.

Nigel Atkins

Cedric,
another matter you might want to ask about is the Optronic rotor blade(s) - when I had the Lucas kit I was advised to buy an extra blade in case the first broke, I do not know if Lumenition has the same problem but if so you want a spare set.

https://autocar-electrical.co.uk/products/optronic-ignitions/optronic-fitting-kits/fk116

£37.20 for MS4 coil -
https://autocar-electrical.co.uk/products/optronic-ignitions/standard-optronic-ignition/ms4

ETA: I thought (a) misfire was from one cylinder.
Nigel Atkins

Hi Nigel,

Thanks for the data ! I am looking out of Lumenition for a replacement coil as I have bad experience with this one now...if it is proved it comes from the coil ;) And also, they are more expensive, so no real obvious reason to stick to them I guess... Would give a try to another brand :)

For misfiring, I didn't expose everything here to not bother everyone :) I am going for the obvious and easy check first (who said battery ? :)) and then post again if I am stuck - as often...
CH Hamon

Fair enough, get the gold Viper then it will look like the sports coil (add a pin stripe and call it Supersport).

But first check your current one is actually leaking.

Sorry I misunderstood by what you meant about leaking at the coil connection point, I was thinking you meant it was leaking from the inside of that point rather than running down the outside of that connection.

Obvious first checks for misfire on one cylinder are plug, that HT lead back to checking dissy cap around that connection.

Willy will be in bed now but I know he'd confirm about the battery and its (earth clamp) connection.
Nigel Atkins

Cedric, the ballast resistor idea ensures that the ignition voltage, hence spark, stays high whilst starter is operating. All coils have internal resistance but the ballast based one is lower. With electronic ignition, it shouldn't matter which is used, might as well use a non-ballast.
Bill Bretherton

Cedric. The coil used with the external resistor, and having about 1.6 ohms internal resistance, is designed to run with about a 6 volt input when the ignition switch is in the "run" position. There should be a second wire, coming off the starter, which provides a full 12 volts on start up and with the ignition switch in the "start" position. When the switch is allowed to move back to the "run" position, the voltage comes through either an external ballast resistor or a resistance wire.

When replacing a nominal 6 volt coil with a nominal 12 volt coil (having about a three ohm resistance), you have to rewire the system so that it is providing a full time 12 volts to the coil with the ignition switch in the run position. As I remember it, I removed and tied off the original wire, then ran a new wire off the white wire system from the fuse box.

Either coil will work fine when wired properly. The nominal 6 volt coil was introduced about 1975 because the North American specification cars were so hard to start with the required emissions control system. Hence, the factory modified the system to provide, for a short period, a hotter spark (and possible increased voltage) when starting. In theory, it also resulted in longer points life due to the lower voltage being passed across the points.
Les
Les Bengtson

Cedric
There are differing views on the subject of bypassing the ballast when starting on electronic ignitions
Usually electronic ign. will improve starting; eliminating the need for voltage bump up at cranking time
But if there is a hard starting car (usually a larger v8 or similar that draws lots on the battery when cranking) then there is nothing wrong with and probably beneficial to run a external ballast coil with a ballast bypass for starting purpouses

To wire it up for this you need a 1.5ohm coil and an external ballast and the external ballast is bypassed with 12v direct to the coil when cranking

Les
Really we shouldn't be calling them 6v coils they are 12v but different internal resistance-most are marked 12v same as the others and some manufacturers are kind enough to write 'use with resistor' on them but lots don't which is what causes all the confusion amongst the untrained buyers
William Revit

Not wanting to hijack the thread but good to see you posting Les.
Peter
Peter Burgess Tuning

We have to bear in mind that Cedric’s car wouldn’t have a low-impedance coil and resistor wire in the loom as standard, so if it has the low-impedance coil, it’s because it’s been added afterwards. Possibly as a consequence of the Lumenition system.

There are two types of Lumenition Optronic, one which uses the standard coil and another which comes complete with its own coil. We really need to know which is fitted.
Dave O'Neill 2

Thanks for all your feedback. I am reading them carefully, few times...

I got the Lumenition coil (LMS4) with the resistance (external ballast) fitted on the car, that's for sure. Then, I can't remember 100% what is connected to what... I had no idea about this different voltage story : at least electronic ignition is less mysterious to me now :)

I will check this weekend, and also see if it really leak or not
CH Hamon

I think the Burton site explains the difference quite well

https://www.burtonpower.com/tuning-guides/tuning-guide-pages/ignition-systems.html
richard b

Thanks Richard for the link ! I tried also to read some website in french : not helpful as I know more technical words around ignition in english now :p

Anyway, I serviced the battery (water, attached, connections,...), cleaned the dizzy cap and went for a ride around 20miles approx. The car starts well and run OK, but i can still feel some misfiring... Don't know if I always had and just start to know better the car or not...

I checked the coil after the trip, and there is some oil marks again. The connection is not flodded, but some oil escaped for sure...

So i did check who is connected with who and also made some voltmeter reading
- what do you think ?
- which coil to take ?

Thanks !
CH Hamon

pic

CH Hamon

Cedric

Is your Lumenition the standard 'Optronic' with the silver module (on the left of pic) or the 'Performance' version, black module with black coil (right)?

Dave O'Neill 2

Your diagram shows 'R' which I am guessing is a resistor. Correct?

On my race car, I had the 'performance' version, but didn't have a ballast resistor.

I still have a performance kit in the garage. I will check the wiring diagram.

Also, it looks like you supply voltage to the coil is going to the terminal with the W/B wire, which is the tacho pulse and should - assuming you have a RVC tacho - be on the -ve side.

Dave O'Neill 2

I looked and looked at the diagram and then realised there would be more connections out of the electronic unit going to the dist than on the diagram
I'd imagine the tacho drive is from the electronic unit and that W/B wire is in fact the 12v bump up wire for cranking , it's on the correct side of the resistor for that
Chris
If you are going to retain the ballast resistor then you need a ballast resistor compatable coil with a resistance accross the primary terminals of aroud 1.5 ohm

If you want to hook it up with a normal 12v coil it should be a coil with a resistance of around 3ohm (2.5--3)depending on the coil
To do this you would remove the resistor and connect both the W and R wires from the resistor direct to the B terminal on the coil

Personally I would leave it as is and get an external ballast compatible coil (same as what is or should be on it with the wiring like that) with a resistance accross the primary terminals of around 1.5ohms

Have you measured the resistance of the coil on your car,that will tell you which coil you have, just remove the wiring off one side to stop interference and measure accross the two terminals of the coil
William Revit

Willy

A ‘72 wouldn’t normally have a ballast wire/resistor, or cranking feed. W/B wire would either be to points or tacho - cranking feed would be white and green.

Also, Cedric has previously mentioned a Lumenition coil, I believe, which is why I was trying to establish which module he has.
Dave O'Neill 2

Yes Dave but it wouldn't have points being a luminition setup would it - ? and he has a resistor in his drawing and that W/B wire is on the power side of the coil which could be anything really including a mistaken W/G

What year model is 'L' reg (the car)

To make it easy why not just measure the coil up so we know what's there
William Revit

DaveO,
the module is silver with a coil that is silverish in colour, only assuming, always a dangerous thing to do, that the coil is still the original Lumenition as I can't remember noticing any markings but I wasn't looking for any as I was totally distracted by something they'd never allow in racing.
Nigel Atkins

Ha ha----Maybe the W/B goes to nothing and is a redundent wire that used to go from the other side of the coil to the dist when it had points, the other end is probably hanging there near the dist.
William Revit

Cedric,
if the coil is leaking that much and you don't know how long it has been leaking for then you need to replace it as soon as possible as it could make the car undriveable and let you down - prevention is better than cure. Your girlfriend would not be happy if she is in the car when it starts to play up or breakdown because you had not replaced a part you knew might cause these problems.

There are a lot of spade and other connections in the system, those and the wires all need to be in good condition and clean, secure and protected.

Electric connections, especially the larger main connections, need to be secure - and not moving around.
Nigel Atkins

Willy,
it's claimed (and may well truly be) as a December 1972 (remember that got the owner "free road tax" rather than being a Jan 8th '73 forward car that would have previous missed out as I know, twice).

It's on a dynamo and the alternators were supposed to have been fitted from December '72.

I can't remember about wiring for that year's model and would confuse myself and others if I thought about it or tried.
Nigel Atkins

Morning :)
You are earlier riser than me :)

To answer the questions :
- My car is from August 72
- I have the silver module
- The (LMS4) coil is 1.5 ohm
- The external ballast is 1.5 ohm
- I do have another W/B wire hanging :D

=> What would be the difference between getting a 1.5 ohm coil and keep the external ballast, versus remove external ballast + actual coil and get a new 3.0 ohms coil one ? Less part is better no ? :)
=> Any recommendation on coil, except this "viper" one ?

CH Hamon

I have been busy Nigel :)

(i was complaining to Nigel about misfiring with battery leads not tighten, and no battery fixation system to the car...)

CH Hamon

Willy,
some instructions for you -

general system description -
https://www.gsparkplug.com/media/wysiwyg/technical-information/lumenition/Optronic_Description.pdf

PMA 50 Power Module Fitting Instructions (with wiring) -
https://www.gsparkplug.com/media/wysiwyg/technical-information/lumenition/PMA50_installation.pdf


MS4 coil -
https://www.gsparkplug.com/media/wysiwyg/technical-information/lumenition/MS4_Instruction_v1-4.pdf
Nigel Atkins

Cedric,
see Willy's post of 04 August 2019 at 02:14:48.

Well done on getting a battery clamping kit fitted, getting those metal hooks fitted are great fun (not).

Not necessarily a priority now if they both fit well but personally I would change both of those battery post connector/clamp and cables as they are the start of the electric system for the car so need to be good to help and make up for any poorer/weak connections currently in your circuits.

Along with many other causes a faulty dissy rotor arm can give a misfire but see what happens after you have replaced the leaking coil.

Bloody so-called smart devices can not present a photo properly, bin it and get a camera.




Nigel Atkins

“What would be the difference between getting a 1.5 ohm coil and keep the external ballast, versus remove external ballast + actual coil and get a new 3.0 ohms coil one ? Less part is better no ? :)”

There isn’t any benefit of running with a ballast resistor if you don’t have the wiring for increased voltage when cranking. Can you tell us what connections you have at the starter solenoid?
Dave O'Neill 2

"Less part is better no?"

Absolutely, keep it simple! Get a 3 ohm coil and leave out the ballast i.e. make sure you have full battery voltage at coil with ignition on. It's an A series. It'll start with a couple of torch batteries ;-)
Bill Bretherton

Hi,

I did check the starter solenoid (hopefully one day I will be able to answer without going to check on the car....), and I am wired as origin : two big cables + brown + white/red...

Thanks for posting all the documentation Nigel !
CH Hamon

The battery clamp is on the wrong way and that looks a strange place for the washer bottle to be.

Trev
T Mason

Hi Trev,
I wanted to put it differently (I guess how it should be), but I realised that the clamp was touching the two terminals of the battery... Maybe my battery is not the best fit for Midget ? But thanks for checking :)

For the coil, I am still confused...
=> Do I need to have anything connected on the "SW" of the coil ?
=> On the installation documentation posted by Nigel (extract enclose), they say that the RED wire should not be connected on the coil... Why ?
=> If i remove the resistance, I can connect the WHITE and RED together, remove the resistance and leave the SW port empty ?

I know so much more, but still so less :) I just understood what SW and CB mean AND do :)


CH Hamon

So maybe I didn't... I need to always have 12V on the SW ? The electronic ignition replace the CB to create the switch, but don't provide the "12V charge" ?

Hum....
CH Hamon

What do you think of the Lucas DLB105 ? :)
CH Hamon

" I need to always have 12V on the SW ? The electronic ignition replace the CB to create the switch, but don't provide the "12V charge" ?"

Yes. You need the white 12v supply to coil SW.

Also yes. The Lumenition is just switching the CB terminal to earth, as the points would.

The Lumenition needs 12v on the red wire. I thin kthe reason they say not to connect it to the coil SW terminal is because on cars with the RVI tacho, it can interfere with the tacho. If you have the RVC tacho, I don't thin kit matters.

Do you know which tacho you have? It should be marked on the face.
Dave O'Neill 2

"What do you think of the Lucas DLB105 ? "

I have no direct experience of it, but many current Lucas branded products are believed to be of variable(?) quality.
Dave O'Neill 2

"Do you know which tacho you have?"
Hum....
"It should be marked on the face."
Ah ! RVI !

"many current Lucas branded products are believed to be of variable(?) quality."
Hum...That might not help me to confirm that the coil is the root cause of my misfiring, if the new coil might be of poor quality :p
CH Hamon

OK, the first thing to do - for the short term - disconnect the white/black wire from the coil.

That would normally be connected to the CB side of the coil and the other end - which you say is dangling - would have been connected to the distributor. You now have this wire connected to the power side of the coil, so if it should short to earth, it is not good.
Dave O'Neill 2

Cedric,
DLB105 IIRC was advertised somewhere as 2.8 ohm which would have it in Willy's 2.5-3 ohm range for a 3 Ohm coil.

The last Lucas DLB105 I bought is still on the car working fine, I would have to look to see if the manufacturer date sticker is still on it.

If you could borrow a know fully functioning coil you would know if its replacement helps which I would think it would.

Your rev counter might be RVI 2430/01(?).

Trev,
the battery clamp is that way round because on the 038 battery the posts are close to to the front off the battery (rather than rear as with original batteries). The clamp is certainly doing a better job of securing than the previous arrangement of literally nothing.

I am not sure that the washer bottle is too far off standard location, although it might be nearer the heater box and battery than usual the photo might exaggerate the difference.
Nigel Atkins

It must be the photo then as the posts look nearer the back than the front to me.

Trev
T Mason

Trev,
it must be the size of the screen you're viewing it on which is why I blew up the image as well as rotated it - or, it's yer eyes wot need sorting.

038 battery post position and type -

Nigel Atkins

Nigel I'm fully aware of the post positions but to me in the current position the clamp looks about half an inch away from the post whereas with it on the other way it looks like it wouldn't come beyond the white stripe and the filler plugs are that side too which suggests the posts are nearer the back than the front.

Trev
T Mason

Bulkhead is on left of photo and heater on the right. Posts are nearer the front. Sliding a piece of bicycle inner tube over the clamp gives some peace of mind that it won’t contact the posts. I use butterfly nuts as they’re easier to tighten.
Simon
S Holt

Trev,
sorry I see what your're saying (I think), if you turn the battery round the post would be on the opposite sides so at least the live cable would need to be longer.

If the clamp strip and battery are the same as mine, with the posts in the position in the photo, the clamp strip gets far too close to the posts for comfort, even if I had a thin piece of rubber to act as an insulator, and I have cut out clearance on the clamp strip for the posts, I find the clamp strip waves around when I try to get it off and once did touch both posts.

I found trying to fit the clamping strip with the supplied (thicker) rubber strip made the fitting even more fiddly and it didn't seat well to the battery.

S Holt's posts reminds me that I had wing nuts too at one time, wonder what happened to them.
Nigel Atkins

Cedric-
As I see it--------
On your car-
White wire = power feed 12v from ign switch
Red wire = 12v power feed wire to electronic box
Brown(latermodels violet = on/off duty wire to coil (marked P on your diagram-pink-? )
----
The early tacho on these cars had a W/blk wire from the CB terminal on the coil, up to the tacho,did a loop round a sensing post on the tacho and then back to the distributor-
As the points in the dist opened and shut,this wire was either open circuit or sunk to earth, operating the ign coil and creating an on/off magnetic signal at the tacho post, How your tacho is working without a full circuit through this wire from the coil to the dist is a bit of a mystery-As Dave has noted the W/blk wire would normally be on the other (signal) side of the coil--
The only thing I can think of is that your tacho has been swapped out for a later one or has been modified to suit--then they have used the original W/blk wire from the coil now on the SW terminal to sense the signal and no need to have the other end of the wire connected (possibly cut off up at the tacho maybe)--The only way to know is to take the W/blk off the coil and see if the car still runs and if the tacho works--If it starts and runs but no tacho,then this is what has happened--put the wire back on and leave well alone but tape up that loose end at dangling near the dist, just in case

Now, the coil-
You mentioned that the diaghram said not to fit the red wire to the coil----yes and no-
What they are saying is--The red wire is the 12v supply to the electronic module--IF" the system has a resistor, they are saying the red wire goes on the 12v side of the resistor, not the coil side which wouldn't have the required full 12v
If you are going to a 3ohm coil you can put the White and Red wires together on the SW post of the ign coil and the violet(P) wire on the CB post

There is an issue sometimes with electronic ignitions with 3ohm coils, -if the red wire gets it's power at the ign coilSW terminal there can be electrical interference into the red wire from the coil circuit causing rough running---If this is an issue then the red wire has to be removed from the coil and connected to another 12v power source from the ign switch ,like up at the fuse box or direct up at the ign switch
On the ballast resistor systems it doesn't seem to be an issue as I guess the resistor absorbs the electrical noise from the coil


Personally I'd be tempted to stick to it as is and get yourself a good new 1.5ohm coil

William Revit

Actually, the early tach had the white power feed to the coil looped through the tacho. The later cars had the coil fed directly and then a white/black to the tach. On the later cars, there were actually two white/black wires together in the same connector - one to the tach and one to the dissy.

Cedric's white/black appears to be the earlier coil to dissy wire which someone has just connected randomly to the coil, although it doesn't need to be connected and, as I said earlier, would be better disconnected, in case of shorting to earth.

The RVC tach was fitted from GAN5 128263, which would be towards the end of 1972.
Dave O'Neill 2

Willy,
I take Cedric's P to mean purple (which some may call violet because purple sounds too common(?)).
Nigel Atkins

Just thinking - IF the DLB105 is 2.8 ohms and IF that is sufficient for the Lumenition 3 ohms requirement with ballast resistor could the DLB105 also be used without the ballast resistor subject to rewiring connections?
Nigel Atkins

Dave--I stand corrected , thanks, must be getting old--lol
Nigel
You wouldn't run that coil with a ballast resistor Some sports coils get down to 2.4-2.5 and would still be ok
and the same with the 1.5 coils ,I've seen them down to 1.2-1.3 ish

BUT the Lumenition requirement for 3ohms can be just a statement that it needs this style of coil or it could be statement saying it MUST be 3ohms - who knows, not I

It's also interesting that Cedrics ballast resistor is 1.5ohm, most of the aftermarket units readily available are around 1.1-1.2
so I take it that the Lumenition resistor is a tiddle bigger than normal for a reason

I'd be leaving well enough alone and finding a good 1.3-1.5ohm coil to go with the Lumenition resistor

If Cedric's really busting to go the resistorless 3ohm direction I'd be tempted to fit a radio suppressor to the SW terminal where the White and the Red wires are connected to limit any feed back to the unit

Honestly, why fix something that has been designed to work as is ,just get a 1.5ohm replacement coil (from Lumenition-?)

Another question
The missfire that this car has, when does that happen and under what conditions

William Revit

Thanks Willy. I'm with you, get the Lumenition specific coil or IF Powerspark confirm that their Viper is suitable then that is an alternative because of the bad experience with the current Lumenition coil.

Whether the coil is contributing to the misfire or not it will need replacing sooner than later at the rate it's leaking.

As the battery was living entirely free-range and the battery earth connection was loose I thought resolving those might help the misfire but thinking about it now IIRC it was only on one cylinder so investigating plug and lead was suggested followed by dissy cap.

BTW I can't read the label on the DLB105 I have fitted to see the date of manufacture but it was fitted 11 years ago this month.

52 posts but covering three of four issues.
Nigel Atkins

I've just read up on Lumenition and a 1.5 ohm coil is specified together with ballast so I stand corrected! It seems odd to me, electrically speakng, that this coil is specified because a full 12v coil, nominally 3 ohms, is using more of the available energy hence, in my mind, generates more magnetic flux. The lumenition coil either has fewer primary turns or has thinner wire in order to maintain same no. of turns as a 12v coil. To me, the only advantage of a ballast system is improved starting in cold conditions or for larger, high compression engines as Willy says. A properly maintained A series car should start easily.
Bill Bretherton

What an idiot I am. Ignore my ramblings about the battery. For some inexplicable reason I was thinking the heater side was the bulkhead and now I've no idea why. Must be dementia creeping in!

Trev
T Mason

Nah Trev, just going a bit sealion!

Simon
S Holt

My Lucas Sport coil is due to arrive tomorrow !
I have read (and read and read) your adivses and comments really carefully, and decided to do differently : that's part of the British DNA, isn't it ? ;)

My plan is to connect the red wire to the fusebox, put back the white wire on the coil and remove the external resistance (assuming Lumenition meant circa 3 Ohms....).
Writing it make me think.... I plan to connect the red wire on the same fuse as the fuel pump
=> Should I increase the fuse value ? As I would expect more current consumption....

Regarding the misfiring, it is hard to know as I changed a lot of things (cleaned plugs, serviced and attached the battery, soon new coil) and I am not so experienced on A series engine (or experienced at all :)) so I might misinterpret...

Let's see anyway when the new settings will be done how the car behave :) Might take some time, as I will be away from my mistress for some days.... I keep you inform, for sure :)
CH Hamon

Although there is/are white wire(s) in the fusebox, they are on the unfused, ignition switched circuit.

The ignition coil and fuel pump are on this circuit, so yes, that's fine for the Lumenition, but no need to change the fuse, as that is for the green circuits.
Dave O'Neill 2

Lumenition fitting instructions, courtesy of Merlin Motorsport, say:-

"SUITABLE FOR coils or coil/ballast combinations of not less than 3
ohms."

I think circa 3ohms should be OK.


https://www.merlinmotorsport.co.uk/files/transfer/technical/doc/optronicinst.pdf
Dave O'Neill 2

Dave , it's interesting they quote not less than 3 ohms
I imagine it would be hard to find a coil over 3, most sports coils are closer to 2.5
Like you I think he'll be ok with the 2.8ohm Lucas coil, but it's still interesting that Lumenition say 3 and that their resistor for the ballast system is higher resistance than most available for this use
William Revit

I am happy to see the interest of experienced members in my trials :)
Be patient, I will "soon" be able to update you and increase your knowledge :)

(French is always modest :) )
CH Hamon

Be sure to have your ‘extincteur d'incendie’ ready 😀
Dave O'Neill 2

If you get the coil wrong it causes a misfire. 🤣
Nigel Atkins

Good evening,

No fire in London, at least caused by me :)

********** Regarding the coil **********
The Lucas Sport (2.8 ohms measured) is installed as I forecasted: it has the white of the ignition key on the +, and the purple of the electronic ignition on the - (or opposite, I forgot :))
The red of electronic ignition is taken on the fuse box, and the resistance is removed.
Also, spark plug gap is now set at 0.35in.

=> Everything works....as before. Or maybe a bit better when warm, but could be placebo effect...
=> Main difference is that the coil is really hot now! I went for a few miles journey, and I can t hold the coil in my hand after it: should I worry?

********** Regarding the misfiring **********
I still have it, and I would say it mainly happen when the engine is cold: after starting the car, it doesn't keep idle with the choke, and after few tenths of seconds without moving, stall. After re-starting it, it is hard to keep it at idle: I need to send her in revs using accelerator. Then I went for a journey, and stalled again after 1 mile at a red light, and it was really hard to restart the car... I don't know if it is link, but when I finally succeeded to restart it, it looked like I had not clutch for a while: impossible to engage 1st or any other gear for some time...
Then, when the car is warm, it looks like all this disappears!

I might have one lead: I first started the car with the previous coil for 1 minute or so, and I saw that the exhaust was having a black smoke... Then, when I removed the spark plug to increase the gap, I noticed that cylinders 2 to 4 were having plugs with oil on them....
=> What are your advises? :)


Sorry for the long text, hope it is interesting and understandable
CH Hamon

The coil would normally run on the edge of too hot to hold
Sounds like your carburettors need setting up properly for a start, but a good basic tune first like valve clearances ,then compression test etc
With your coil running hot - they do
but with wider gaps it will run hotter
try .025" and see if it runs a bit cooler .035" is probably too wide anyway, just overloading everything for no reason
That coil isn't up to the job of big wide gaps, I bet if you took it out for a mad thrash it would break down up at the top end of the rev range with .035" gaps


William Revit

Spot on Willy, back to basics as Nigel would say. It is bad to try and guess faults from a description, but, it does sound like the carbs are flooding/way too rich at idle doesn't it?
Peter Burgess Tuning

Thanks for your feedback! I will close the gap of the plugs (start to get use to this job...)

No comment around the black smoke and oily spark plugs when engine is cold? I would think that is my main problem...?
CH Hamon

Peter and Willy have commented on your black smoke & oily plugs. But is your choke operating / being operated, correctly? At this time of the year you should barely need a choke to start it, and even then, only for a few minutes of running.
GuyW

Morning guy :)

Sorry, I was more trying to understand how the spark plug can get oily...

I read those two archives, and it looks like I have similar issue:
https://mg-cars.org.uk/cgi-bin/or17?runprog=mgbbs&access=&mode=archiveth&subject=97&subjectar=97&thread=2011043012481118717
https://mg-cars.org.uk/cgi-bin/or17?runprog=mgbbs&access=11144101704047&mode=archiveth&subject=97&subjectar=97&thread=2001032616430026911

Hope it is not a cracked ring :/ Need to find a compression tool to test...

Also, I removed the rocker cover yesterday: is it normal to have so much oil on the top ?


CH Hamon

Er, no it is not normal to have so much oil on top like that.

0.35" would be 8.7mm - but even at the 0.035" you meant that would be a lot wider than the 0.028" I said Peter found was best for my car on the rollers but standard (by the good book) 0.025" wasn't that far behind IIRC so either might be a better place to start than the 0.035".

Nigel Atkins

Hi Nigel :)

I missed this 0.028" information... I read 0.035" on some different topic, hence this setting.
With all the feedback here, 0.028" sounds good to me :)
=> Is your coil hot too..? Can you "hold it" after a journey ? I will check again after closing a bit the spark plug gap as said

Regarding oil, I am concerned you are... Anything to check ?
I bought a compression tester engine, waiting for it now :)
CH Hamon

Cedric,
If the car was standing on level ground when you switched off and took the valve cover off, then no, it shouldn't have that much oil on top of the head. Otherwise, the cause is likely to be worn rocker shaft or worn rocker bushes. This allows too much oil to be pumped out from the rocker shaft and it floods excessively onto the head. This in turn can cause oil to swamp the top of the valve guides and run down the valve stems, causing oiled plugs and oily combustion chambers.

The rocker shafts wear on the underside because of the upward pressure of the valve springs and push rods. Completely slacken the valve adjustment on one or two sample valves and pull the rocker to one side along the shaft. Then feel the underside of the shaft with your fingernail to see if there is a worn step or ridges there. If there are, then you need a new rocker shaft and may also need new rockers. These can all be changed with the head still in position, there's no need to remove the head.

Ohh, and the reason I asked about your use of the choke is because this could also cause the plugs to look oily and would create the black smoke.
GuyW

Cedric,
I can understand you missing or forgetting the 0.028" information as you were probably overwhelmed by the occasion. It was given verbally in clearest Nor'mptun Inglish - along with keeping your foot off the clutch pedal when starting to save the clutch - and possibly discussion of the choke operation being in the good book. I am not too sure about that last item as I was overwhelmed by your (lack of) battery security and its (waggly) connections.
Nigel Atkins

So, I have been doing my homework :) Thanks for your guidance and "what to check/what to do", really helpful.

"Completely slacken the valve adjustment on one or two sample valves and pull the rocker to one side along the shaft. Then feel the underside of the shaft with your fingernail to see if there is a worn step or ridges there"
It is hard to tell... Some area feels really soft, some feels a bit harsh... Maybe like orange skin sometimes in some places, but nothing really outstanding or easy to notice

"Ohh, and the reason I asked about your use of the choke is because this could also cause the plugs to look oily and would create the black smoke"
When you say "look oily", it is because it is in fact petrol ? Mine were oily, I did check by cleaning them on a tissue.
For the choke, I have to admit that I thought of this, and I usually start the car with full choke and warm the engine around 1300-1500 tr/min. Tonight, I started the car with only half the choke, and went well. I then decrease the idle speed to 1000-1200tr/min and...the black smoke disappear :D

I set again the tappets gap, and closed the spark plug gap to 0.028". I feel like my engine is not really stable under 1000tr/min at idle, and make a tractor noise...
- Video at "fast" idle around 1200tr/min: https://youtu.be/FarawbCEV8I
- Video at "low" idle around 900tr/min : https://youtu.be/k23hGGfUFDs

CH Hamon

Cedric
It's hard to tell by video --did it sound like a tractor before--what did you set the tappets to and how--what sequence
I know you want to sort this yourself and appear to be happy to work on the car, but honestly, if I were you, I would do some research and find someone that you can take your car to and get them to have a look at it and advise you what needs doing-
We can go back and forth on here forever but actually being where the car is and seeing, hearing it in the flesh is completely different
Someone that knows these cars might just touch it and say your choke is sticking and all your problems, or most of them are fixed or sticking carb pistons,-could be anything
It could be simple----or not
Same with your rocker cover, if that had been a bit loose or the gasket gone hard and it had been recently running then I'd say that amount of oil on where the gasket sits wouldn't be all that far off normal---again, seeing it in the flesh is the issue

Again though, a good basic tune, get the carbs all clean, float levels and mixtures adjusted up and get the linkages all set up properly and working freely, consistently and magic things can happen
William Revit

True Willy...

But it is funny to DIY :) And I am learning a lot :) Not sure I am ready for carbs yet though...

Will you want to see the compression test results still, when I will have it ? :)
CH Hamon

Hi Cedric, just remember to have your foot flat on the accelerator pedal when you do the compression tests
Peter Burgess Tuning

Cedric, if you still have a lot of noise from the top end it could still be valve clearances too loose.
A common mistake is to use a feeler gauge that is wider than the end of the valve stem. This means that if there is a worn "track" in the end of the rocker (which is normal) the gauge will bridge the gap and give a false clearance.
It's actually quite difficult to buy gauges that are narrow enough, I had to grind mine down to fit.
Also if there is significant wear in the rocker shaft or bushes they will always be noisy, no matter how carefully you adjust them.
(That's exactly why my rocker gear is noisy, by the way).
Hope that helps.
Greybeard

Cedric
Yes it is nice to DIY
I wasn't against that at all, I'm all for it,
I'm just saying, it might be worthwhile getting someone to have a quick look and tell you if you're going the right way
""Will you want to see the compression test results still, when I will have it ? :)""
Yes of course, not going anywhere, but thought if it was noisier than before the valve clearances were done, maybe the method of resetting them could have gone a little astray and if so this will probably effect the comp. test, and the way it runs
William Revit

Thanks Peter and Greybeard for your comments, make sense ! Well noted ;)

No worries Willy ! For sure she deserves a run on rollers ;) But I want her to run nicely before, and use specialist 'time for tuning, not debugging the car... Maybe Peter can give some advices around the best moment to put the car on rollers :)

Did drive yesterday to Ace café (and meet other BBS members and lovely Midgets ;)). She did drive really well, even 70mph on the M1 after a detour to push her a bit when warm. Still wonder if all the changes I did improved the car, or if my problem only comes when the car stay parked for few days (oil slightly going into the chambers)
=> Time (and compression test ?) will tell ! :)
CH Hamon

Cedric,
your car is stay a fair way off getting a lasting effective tune-up on the rollers. I am sure Peter would make improvement and possibly be able to suggest other engine work required but it would then need the roller re-tuning done again as things and setting would have change.

Do remember the engine and carbs are low priorities on the car as you have already found on your previous Midget brakes, steering, (tyres), suspension and light and windows are much more important. Unless the engine and carbs are very bad normally you can continue to use without creating too much further work - that is the problem with these cars they can be run in poor condition and many owners do not even know or accept how poor the condition is.

If you have serviced the rest of the car you can get on with the engine and carbs more but I think checking the battery and its is very early on in the Driver's checks and servicing yet that had not been attended to many months into your ownership. You are getting into newby and macho mistakes of wanting to play with big-boys toys and get into technical issues before you have finished (or even started in some cases) dealing with the basics.

IF you have fully dealt with the basics then I apoligise and you carry on with more fiddling than driving.

Based on your posts and you saying your car drove more or less as mine then I am now worried that my Midget might not be in the reasonably good condition I thought it was and I will need to do the same as you and drive other Midgets in good mechanical running condition to see where mine lacks.
Nigel Atkins

Uhm, sorry a few typos -

>>your car is -still- a fair way off getting a lasting effective tune-up on the rollers.<<

>>and -lights- and windows<<

>>checking the battery and its -connections are- very early on in the Driver's checks and servicing<<





Nigel Atkins

Still on the basics, didn't finish Greybeard's book yet :P

Your car does feel better than mine ;) Only the color is better on mine :P
CH Hamon

Cedric,
can I suggest you start with the Drivers Handbook before going on to Grey's book, pages 7-11, pages 15-75, pages 85-88 and pages 111-127.

I agree the paint colour on your Midget is much better than my boring-old-man's-red but no good you back-pedalling now on your comment that your car more or less drove the same as mine - realising this I've taken my Midget off the road and will not drive it again until it is improved and I find the reasons for the deficits. A very long list is being compiled now.
Nigel Atkins

and--I wasn't saying it needed a dyno session, just getting someone who works on these cars to have a quick look and some guidance as to if your noise is normal-? or whatever, or
William Revit

Hi,

Did play with the car today, between showers: (weather) timing was not so easy today ;)

So for compression, I did as you told me : I get 125 PSI on cylinders, slightly less on the 3rd (120+).

I noticed that the plug looks better now. Also, I removed the rocket cover to change the bushes on it and try to flatten it, and noticed much less oil in the head: I do feel better about my engine condition now :)
CH Hamon

This thread was discussed between 30/07/2019 and 18/08/2019

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