21 replies to this topic

[Kev Shepherd]

Hello all,
I have a quick question about electronic ignition. I have a 1980 998cc fitted with electronic ignition and it has developed a misfire on No3. I have tried new plugs, swapped HT leads and it still has the misfire. I did clean the distributor cap terminals as they did have a bit crud on them, especially No3. I cleaned them up and refitted it....thought I'd cured the fault, no such luck.
No3 plug was sooted up, the others were pretty good. Do you think the cap could be an issue, possibly cracked? If so, can I fit a normal cap? It is a electronic ignition, but I do not know what brand as I can't see anything printed on it.
I have also done a compression test, all four were the same and also checked the valve clearances.
Thank you in advance for any help you could offer.
Cheers,
Kev

[weef]

I do not think that there are any differences with the distributor caps. The electronic distributor only acts as a switch to trigger the ignition coil and does in no way enhance the spark intensity.

It may be worthwhile replacing the rotor arm at the same time.

[sonscar]

Check for free play on the shaft.Is the misfire regular chug chug chug? Or intermittent?How sure are you that it is limited to no three?,Steve..

[Kev Shepherd]

Evening,
Thank you for your replies, I will replace the cap and rotor arm and the misfire is occasional. Under load the engine pinks. It'll go along at 55mph and be fine. At slow speeds the car is sluggish initially then picks up. I will check for play when I am next in the garage.
Cheers,
Kev

[nicklouse]

Caps are not special. You just need the correct one to fit the dizzy body. There can be options on lead orientation but that’s it.

[Cheeser]

Yes just get a standard cap and rotor arm, either nos or from Distributor Doctor, avoid new Chinese rubbish!

[Kev Shepherd]

Thanks for the advice, will order from Distributor Doctor. Have had a run in with Lucas parts recently. I have a 1972 T120R Bonneville and purchased a new Lucas ignition switch....it never worked properly. I didn't realise until then that Lucas had been sold off.

[Ethel]

There was an electronic specific cap, coloured blue. Doubtful the difference was much more than the colour, certainly not enough to make a standard cap not work.

 

We're all assuming it's not the factory fitted 65DM4 electronic dizzy off later models, that has screws in place of the spring retaining clips.

 

If you can't get rid of it, the rotor arm is in control of the firing order, so you could turn the dizzy body by 90 degrees & reposition the plug the same in the opposite direction on the cap so they match up with the rotor arm again. Of course you'll have to reset the timing, but you'll be able to say with more certainty if the fault is in the dizzy.

 

It's an A Series, so it could as easily just be varying degrees of "bangability" in that cylinder. A compression test may be worthwhile and reducing the gap for that plug may make just enough difference.

[Kev Shepherd]

The distributor looks like an aftermarket part, can't see any numbers stamped on it. I have taken photos, but can't see if I can add them to this (Not very tech savvy!). I have also rocked the rotor arm to check freeplay and I'd say it moves around 2mm.
I have done a compression test, but numpty here didn't write down the results! They were all pretty close, one was a fraction lower....not sure which one. Will do another test soon.
Rotor arm and cap on order from Distributor Doctor, hopefully be here in a few days.
Cheers,
Kev

[Ethel]

Compression tests are very subjective, as much a measure of the battery & starter motor. If the results were similar that's good enough.

 

The rotor moves against the springs of centrifugal advance, so it should rotate but spring back to its rest position.

[Kev Shepherd]

Right, here's an update. New cap and rotor fitted (only ordered them yesterday afternoon!). It still ran rough, whilst it was running I then noticed sparks going across the coil, from the positive to the HT and same with the negative. Took the coil off and cleaned all the gunk off it, then took it for a spin. For the first mile it appeared to go better than ever, then a bit of spluttering when accelerating at slow speed. Once at speed it was fine, but on idle when at a junction it want to cut out. Drove to the petrol station (about 5miles away), filled up with E5 and started her up. Sounded perfect and instantly acceleration at slow speed was better, if a little 'fluffy' and idle was was fine, not the new fuel as it didn't have time to get down to the carb.
So, it idles OK and when I remove the HT leads, No3 doesn't appear to affect the running, which is odd because I was doing 55mph no problem, no lumpiness in the engine. When I hold the HT lead just on the plug you can hear the spark. Is it a case of if it ain't broke...?!
The thing I notice now is that idle and at speed with the foot down it pretty good, it is the first quarter of throttle that appears a bit 'fluffy', almost hesitant, the engine labours for a couple of seconds and then off we go.
Sorry to keep this thread going, really appreciate your help.
Cheers,
Kev

[Kev Shepherd]

Taken the plugs out, No3 is slightly sooted up, the other three look pretty good

[sonscar]

Change no3 plug with one of the others and see if the fault moves with the plug or stays with the cylinder would be my next move,Steve..

[bpirie1000]

What isnthenexhaust doing on idle.. Is she smooth or lumpy? I trust no smoke or funky coloured emmissions.

Maybe take it round local garage and get them to down emmission test.

Ideally the rolling Road is the best place...dsashpot oil all correctly filled?

[Kev Shepherd]

Evening,
I'd say the exhaust note was in between if that is at all possible! Not too bad, definitely not like it is running on three cylinders and no scary smoke. Funnily enough I did top up the dash pot, that would have an effect on it then? It has been a few years since I had a Mini.
Cheers,
Kev