14 replies to this topic

[ODD1991]

hey guys, i cant get the old girl to start, it has been running fine for a while but now it aint having any of it, i replaced the ht leads dizzy cap and plugs and now ive noticed arc on both the coil and the dizzy cap. could this be down to a bad earth or something more complex?? its a metro 1275 with standard electronic ignition.

[tiger99]

If it is arcing across the insulator on the distributor cap or the coil, it means that there is too much voltage, because the current is not going through the spark plugs. Obviously the king lead is ok, or no voltage would reach the distributor, but either all the plug leads are open circuit, all the plug gaps are ridiculously wide, the rotor arm is missing or not lining up with the four electrodes in turn (pointing to the gap between, either fitted wrong or for opposite rotation, or cap fitted wrongly, which should be impossible), the rotor arm is the wrong type (too short, there really are different sizes) or the carbon brush is missing from the centre of the distributor cap. There are no other places where the coil secondary circuit could fail.

It is only logical to consider the parts which you have replaced to be prime suspects. I suspect the carbon brush ot its spring as being the most likely, followed by incorrect rotor arm.

Oh, and are the leads pushed tightly into the distributor cap? Pull back the waterproof boots, push the leads in tightly, and then pull the boots down on to the cap.

Edited by tiger99, 14 February 2012 - 11:11 PM.

[dklawson]

There is also a slim chance that you have conductive contamination on the coil and the distributor cap. Carefully clean the outside of both with a clean paper towel sprayed with WD-40 or similar.

[tiger99]

That is possible, but it would be unusual, on both the cap and the coil. But who knows what kind of pollutants are out there? To think that people might have been breathing it.....

The very worst contamination for anything electrical is carbon fibres, which can be released when the material burns, or from the factory, wherever that may be. Normal drilling and cutting is ok, because it only releases short lenghts of fibre, but long fibres readily become airborne, and are so thin as to be invisible.

[ODD1991]

hi thanks for the replies, i checked and cleaned the earth and still the same result, if it aint arcing at the coil it arcs at the dizzy cap vice versa. the dizzy cap is new and can only go on one way, ive checked the ht leads and seems fine, ive got to the point of either replacing all the wiring around the coil or phoning an auto electrician, also the car is popping and back firing when trying to start

[lrostoke]

This is a really long shot and I'm just shooting in the dark.

You can buy resistive HT leads, and also get resistive spark plugs..If NGK plugs they will start BPR as a rule. If you have both resistive leads and plugs I'm just wondering if thats something that could cause your problems. ???

[ODD1991]

hey, the leads are the same as the ones they replaced and the plugs are what is specified in the haynes manual, its driving me bonkers

[greenwheels]

hi thanks for the replies, i checked and cleaned the earth and still the same result, if it aint arcing at the coil it arcs at the dizzy cap vice versa. the dizzy cap is new and can only go on one way, ive checked the ht leads and seems fine, ive got to the point of either replacing all the wiring around the coil or phoning an auto electrician, also the car is popping and back firing when trying to start

'popping and back firing when trying to start ' suggests plug leads in the wrong order.

Did you put the engine and ignition system in your Mini which does not have a ballast resistor that the original Metro would have had, in which case you would have the wrong coil. Confess that I suspect that this would not cause all the symptoms you describe.

[tiger99]

It is nothing to do with the wiring around the coil. You cannot get excessive secondary voltage causing arcing as a result of any fault in the primary circuit. But as a precaution, you could change the condenser as that can influence the voltage. Nothing else on the primary side, even something wrong with the ballast resistor, can cause your observed symptoms. The problem definitely lies somewhere between the king lead and the spark plugs, and I still suspect the carbon brush or the rotor arm.

[ODD1991]

the leads could not be in the wrong order as it was running and i havent swapped the leads at all, this would be the same for the wiring as i havent change nothing from when it was running, next step is the replace the rotar arm?? would a faulty one create arcing at the coil though??

[tiger99]

OK, no condenser, you have electronic ignition, as I have just noticed. That opens up another possibility. Does the electronic system take its timing information from the distributor, or from a crankshaft sensor? If the latter, the spark is happening when the rotor arm is not pointing at any of the plug leads, which explains the problem completely, the high voltage has nowhere at all to go. The cause would be that the distributor timing was way out, or alternatively the crankshaft sensor was grossly misaligned.

In any case, you have a symptom that would be fully explained by the rotor arm pointing nowhere as the spark occurs, and that can only be achieved in conventional systems by the rotor arm being wrongly fitted in relation to the cam lobes, so its position does not relate correctly to the points opening. You might get the occasional spark, wrongly timed, at the plugs, on occasions when it did not flash over the cap, but jumps inside, which would explain the popping.

Can you do some checks to ensure that the rotor is pointing to the correct place, e.g. set the engine to TDC (feel with stick through plug hole if you don't have timing marks) and take the cap off. Is the rotor aligned with the number 1 or 4 plug lead? Feel for compression on number 1, and check that it is pointing to number 1 lead, and number 4 is diagonally opposite. Car in gear, push it forwards so engine turns half a turn, number 1 at BDC (only need to take one plug out), check that teh rotor arm now points to number 3 lead, and the sequence is correct.

[lrostoke]

I just googled for your problem and pretty much everything as been covered with regard to causes

arcing caused by spark finding path of least resistance.

Causes

Carbon/dirt build up allowing tracking..so contaminates on plugs, dizzy, leads

damp

to much resistance ..so my suggestion of wrong combination of plugs and HT leads is viable.

to much gap on the plugs, so spark finds an easier path.

crack in dizzy cap

Another thought, I seem to recall a while back somebody had problems with the internals of the 65D, breaks in the wiring etc. Maybe thats causing it to fire wrong as stated above

Edited by lrostoke, 15 February 2012 - 11:50 AM.

[tiger99]

Yes these things can cause all these symptoms but far more likely, as you suggest,is too much resistance, It is possible that the rotor arm is the wrong type, too short, or with the leading end of the contact segment pointing the wrong way, so it does not overlap the fixed contact properly, which is why I said it needs to be for the appropriate rotation direction. Both exist, on different types of engine. But the king lead contact to the rotor arm, the carbon brush, is even more likely to be the problem, Is it freely moving, not stuck in the retracted position?

Almost all symptoms like this are because the spark cannot get to the plugs, or jump the gap, so something along the way is not making as close contact as it should, and there is only the distributor and the plugs to consider, if the leads are ok, and fully connecting at both ends..

Edited by tiger99, 15 February 2012 - 11:54 AM.

[ODD1991]

the timing is taken from the distributor i believe and has not moved since the rebuild as marks where put in place ffrom intial timing and the distributor is in the exactly same position.

[tiger99]

So that leaves rotor arm and carbon brush.