56 replies to this topic

[gazza82]

Hi Paddy. Thanks.  I just tried this and there's definitely no gap.  I took the opportunity to sand stuff down too (there was black on the rotor arm, but it appeared to be melted plastic rather than carbon from the distributor cap, which is pretty new).  Tried to start and again, no luck.
 
As I am short on equipment (eg, checking the gaps) I hope someone who knows more than me will go through it while I shadow them.  I'll update this again soon!

Not always a good idea to sand things as those can open up the very critical gaps between the rotor arm and cap segments.

Have you changed the points? One mistake a lot of new owners make it to put the insulating caps/washers under the wires and the locating nut in the wrong order. The caps go either side of the spring with the wires on top and under the washer/nut. Check also the second small wire that runs from the points to inside distributor. These are fine wires and can be easily broken.

The black melted plastic on the rotor arm sounds wrong ...

[mullet]

 

Hi Paddy. Thanks.  I just tried this and there's definitely no gap.  I took the opportunity to sand stuff down too (there was black on the rotor arm, but it appeared to be melted plastic rather than carbon from the distributor cap, which is pretty new).  Tried to start and again, no luck.
 
As I am short on equipment (eg, checking the gaps) I hope someone who knows more than me will go through it while I shadow them.  I'll update this again soon!

Not always a good idea to sand things as those can open up the very critical gaps between the rotor arm and cap segments.

Have you changed the points? One mistake a lot of new owners make it to put the insulating caps/washers under the wires and the locating nut in the wrong order. The caps go either side of the spring with the wires on top and under the washer/nut. Check also the second small wire that runs from the points to inside distributor. These are fine wires and can be easily broken.

The black melted plastic on the rotor arm sounds wrong ...

 

Thanks Gazza.  I used 300+grit just enough to get this plastic off.  More polishing than sanding.  The rotor arm seemed to collect it from the new cap, like getting "worn in" and took tiny amounts of the plastic with it.  I've changed no parts.  I will see if I can get good close up photos inside the distributor today.

[mullet]

Hi all.  To update: had a teleconference with a mechanic relative.  He agrees the low tension side seems OK, any anything within/from the coil seems to be the problem.  Engine itself is grounded, we went about changing all fuses and sparkplugs anyway in case there was something wrong not visible to the naked eye.  Also tested for a spark on new plus and nothing.  There is fuel in the line and on removing a new sparkplug after turnover, it did smell of fuel.

 

Whether there's some block in the carburetor, I don't know.  But there's definitely no spark so still thinking the problem is electrical.  

 

All that to say, he thinks it is worth changing the coil either to permanently repair or further diagnosis, at least.  I believe this type is suitable?

http://www.minispare...|Back to search

Appreciate those following the thread would like to diagnose without this extra expense.  Appreciate, also, any last minute thoughts before purchasing of course.

[mullet]

Hi all.  It wasn't the coil (bought a new one, but not so expensive). 

 

In frustration and brute force, got the air duct thing off so I could see the solenoid.  Yellow white goes there via a spade.  Cleaned all connections there. No luck.

 

Followed the pink/white ballast.  Turns out it must have been modified at some point (I guess) and explains why it was so difficult to trace.  See photo.  I wanted to see what volts it had around this modified connection-to-earth.  I disconnected the yellow/white from solenoid and also both yellow/white and ballast (pink/white) from coil.  So it was 100% just that modified connection in the photo, direct to ground.  And it was 12.3volts with ignition in the on position, same as the reading at the battery positive/negative.  I then got 12.3 volts on the connection that goes on the positive coil terminal, so length of ballast cable carries same volts.

 

The 3 white cables at this modified area: 1 goes to the fuse (a new fuse).  2 go inside the dash and haven't yet traced these, but can if anyone feels this is needed. 

 

Does this rule out a bad ballast? (I did read today a failing ballast can cause overheating, and the car does overheat even on a mild summer's day at low speeds/traffic despite flushing the radiator system)

 

Does it seem like the low-voltage side of the ignition is fine then and we should focus on the high-voltage/distributor (if so, will engage my mechanic friend when he is eventually free!)?

 

If it was an alternator problem, we'd still at least get a spark, wouldn't we?  photo_2023-07-15_18-39-28.jpg   44.93K   1 downloads

Edited by mullet, 15 July 2023 - 04:52 PM.

[sonscar]

Seriously the ignition setup is very simple in its construction and operation.Use Google to find points ignition system or Kettering ignition system.The points are a switch the connects and disconnects the coil to earth.It charges up when closed and sparks when the open.
Put your tester on the live lead and the other lead of the tester to the disconnected wire to the dissy and rotate the engine.The voltage should be 12v with the points closed and 0v with them open.Truly it is very simple,please look at how it works and soon you will be a dissy god.Steve..

[mullet]

UDPATE: a couple of mechanics, part of a local classic car club, had a look at tested a lot.  I don't think this was very simple as took a lot of diagnosing, especially following cables (with a slight modification to the ballast wiring). 

 

They pinpointed it to the distributor itself.  The low voltage side checked out, as it did thanks to the useful help I have had here.  Their suggestion is to replace the distributor condensor, contacts, rotar arm and distributor cap.  In fact, even during testing some smoke and ionized smell ommitted from the distributor cap.

 

They also suggest an eventual modification of the ignition system (something others remarked on).  First things first: get it started.  Unless anyone has any remarks or suggestions on this, I'll update again as soon as I have new parts installed.

[mullet]

I await new part.  But can anyone tell me if this is significant?  I followed one of the tests in the Haynes manual.  With the points separated with a piece of card, cap back on, then with ignition in the on position, using a volt meter, I only got 6.3v from + of coil to earth.  I expected it to be more than this as the battery reads at 12v.

 

I then tried a 'jumper' wire from where the ballast resister wire begins at fuse and attached it to the + of coil (bundled into the spade nice and snug with the existing supply).  My thinking was, if there's a damaged wire/insulation in the taped up line of dozens of wire that is 'leaking' power, this might show it.  I then got a reading of 11.1v.  I don't know if this is indicating anything with regards the health of the ballast wire?  Or is that the purpose of the ballast wire and readings are normal?

[Lplus]

If the points are held apart by a non conducting substance then there should be no current flow at all and there should be 12 v at the + and the - of the coil irrespective of ballast wire or other type of wire.  Pull the connectors off the negative terminal of the coil and check the voltages.  If they're 12 V then there's some sort of short to earth between the negative terminal of the coil and the distributor.  Is there a black and white wire leading to the rev counter?

 

Another possibility is the connection onto the points spring should be insulated from the fixing post by a plastic top hat washer.    Is that insulation in place and in good condition?

Edited by Lplus, 15 August 2023 - 07:38 PM.

[mullet]

If the points are held apart by a non conducting substance then there should be no current flow at all and there should be 12 v at the + and the - of the coil irrespective of ballast wire or other type of wire.  Pull the connectors off the negative terminal of the coil and check the voltages.  If they're 12 V then there's some sort of short to earth between the negative terminal of the coil and the distributor.  Is there a black and white wire leading to the rev counter?

 

Another possibility is the connection onto the points spring should be insulated from the fixing post by a plastic top hat washer.    Is that insulation in place and in good condition?

 

Thanks for the reply.  So with card between the points, cap back on, everything connected at coil, I get 6v from + of coil to engine strap (meter point pushed into the brade).  And 1.5v - of coil to engine strap.

 

With -of coil disconnected (and +still connected), I get 11.6v at + of coil and 11.6v at - of coil. 

 

(Use of engine strap brade maybe not ideal, but seems fine-ish as get 11.9v from positive battery-to-engine-cable where it first attaches and then from there with meter to brade)

 

This mini does have a rev counter and it is indeed a black/white (and green-red).  If you have the Haynes manual, this appears to be 12A 36 Wiring diagrams pre-October 1996 models and wiring diagram 17 - all 1984-on carburettor models with multiple instrument pack. It seems to check out in terms of all colours. 

 

I have yet to inspect the distributor.  I trust it is easy to get out (or can it be done - new parts too - just with the grill removed)?  And if slotted back in, so long as the arm remains in the same position I guess this will be fine? The Haynes doens't go into that. 

 

Are there further diagnostics or something else to try first?

[Lplus]

So the ballast wire seems to be working correctly and so the wires upstream of the coil sound fine. If you're sure the card holding the points apart is non conducting it sounds like an almost complete short circuit to earth between the black/white wire at the coil and the points.  That could be a number of things - the wire could be frayed somewhere, the insulator could be missing/damaged where the wires are bolted to the points spring, the condensor could be shorting out inside (I'm assuming a Lucas distributor, a Ducellier one should have the same sort of components but I haven't dismantled one)  Since the black/white wire to the rev counter may be attatched to the same spade connector as the wire to the coil it's also possible the short is in that wire or the rev counter itself since the rev counter shouldn't take any current from there.

 

If the rev counter wire is separate disconnect it or, if not, try to disconnect and isolate the rev counter end  and try again.  If there is no change then the fault seems likely to be in the distributor area.

 

Inspection and points changing should be possiible through the grill, but if you want to remove the distributor, first mark its orientation where the mounting flange meets the block to preserve the timing.  The drive will only fit in one position so keeping the spindle in one place isn't necessary, the vital action is to mark the orientation of the distributor in the block and return it to that position.

 

Any one else see any faults in my logic?

[mullet]

So the ballast wire seems to be working correctly and so the wires upstream of the coil sound fine. If you're sure the card holding the points apart is non conducting it sounds like an almost complete short circuit to earth between the black/white wire at the coil and the points.  That could be a number of things - the wire could be frayed somewhere, the insulator could be missing/damaged where the wires are bolted to the points spring, the condensor could be shorting out inside (I'm assuming a Lucas distributor, a Ducellier one should have the same sort of components but I haven't dismantled one)  Since the black/white wire to the rev counter may be attatched to the same spade connector as the wire to the coil it's also possible the short is in that wire or the rev counter itself since the rev counter shouldn't take any current from there.

 

If the rev counter wire is separate disconnect it or, if not, try to disconnect and isolate the rev counter end  and try again.  If there is no change then the fault seems likely to be in the distributor area.

 

Inspection and points changing should be possiible through the grill, but if you want to remove the distributor, first mark its orientation where the mounting flange meets the block to preserve the timing.  The drive will only fit in one position so keeping the spindle in one place isn't necessary, the vital action is to mark the orientation of the distributor in the block and return it to that position.

 

Any one else see any faults in my logic?

Again thank you for giving your time.  I disconnected the rev black/white at the back of the rev counter (that goes straight to the negative coil per diagram) and the measurements were all the same whether connected or not.  I guess this may rule out the rev counter wire shorting to earth.  Next I guess, replacing distributor parts and see (at least not too pricey) and look for any shorts to earth there too. 

 

I saw long after starting this thread, a google search that returned a thread from this very website of someone who had a similar issue.  Seems google finds threads better than the search here.  Anyway, it started working with the new distributor parts.  He seemed happy, and in the process renewed most of the ignition hunting for the problem, but was happy to have it all renewed anyway.  I'll be trying the distributor replacement parts when they come.

[mullet]

******!!!!!!!!!!!!!!!!!!SOLVED!!!!!!!!!!!!!!!!!​​******

 

Hi all,

 

Thanks to extra final messages of help from Lplus and sonscar, I got it running again.

 

So although I replaced the coil, distributor cap, HT cables, rotor arm, spark plugs, ultimately it was the condenser and points that were the problem.  The set up inside the distributor was shorting to earth.  But I am happy to have new - and spare - parts.

 

I can't say if the jumpstarting caused it (eg, polarities reversed or something), yet it was an incredible coincidence if not.  The ignition progressively got worse after 4 or 5 drives and then didn't start at all.  My guess is the interior of the condenser got damaged, then got quickly worse and eventually caused the plastic to melt as per photo.  And on melting, a very slight contact to the metal of the points' metal spring was made.  That's my theory.  Hope this is clear from the photos.

 

I didn't realise how easy the distributor was to remove and service.  For anyone else with a problem one day, don't be intimidated with this.

 

I've learnt a lot and glad I didn't give in and hand this over to the professionals.  I don't think that would have been in the spirit of this forum and it was all possible due to the excellent advice and patience received.

 

Thanks everyone!!

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