No Spark At Centre Of Dizzy

[Benjamin1983]

I have no spark at the centre of the dizzy cap I've tested for 12volts at the Coil and it is there. I took the car out for it's first trip of this year a few weeks ago and it slowly lost power until it stopped. (It did already have a misfire when I set off). It is not a fueling problem as I've reciently replaced the pump. I checked this at the time I stopped and you could still hear the pump clicking. Further to this of the two lives attached to the coil one is only showing 6 volts and the other is showing no voltage at all.

[amarshall]

How are you measuring the HT at the centre of the cap ?

Have you checked that the king lead is intact ?

[Benjamin1983]

With a spark plug earthed. I have noticed that the lead from the coil to the dizzy does not fit a plug very tightly. All the leads are no more than a year old.

[AndyC]

I'd be tempted to guess at broken circuit somewhere in the pick-up part of the dissy to amplifier circuit , but it's probably best to work backwards.
If there's no spark going into the dissy cap and you are sure there is no spark going into that coil to dissy cap lead then check the coil operation. A basic (very basic) check is applying a known +12v source (just check that the existing one works) to the correct pole of the coil and a good earth to the other pole of the coil. Remove the earth and look for that to cause a spark. If it doesn't then assume the coil to be at fault. Assuming coil is OK then work back to the ignition module and speed limiting unit (which can be removed simply by unplugging the wire).

[AndyC]

Ok, just seen your updated post, in that case I'd suggest you have a broken wire leading from the ignition to the +12 pole of the coil. You can confirm it as the process I put the previous post or simply run a (switched) +12v wire from somewhere (alternator live post seems a good idea) and see if the car runs with it like that. The switch is so that you can switch the engine off without having to rip wires off.

[Benjamin1983]

Would that be why I'm only showing 6 volts at the coil a break in the wire between the coil and key ignition? Just to give you a big picture I have fitted new dizzy cap and rotar arm. I have also had the dizzy off and cleaned up the centre so as the arm makes a good contact. I have made good the two wires from the distributer to somewhere?? As they were touching the starter and had gotten scorched. I have new plugs, recient leads, new dizzy cap and rotar arm. I have also cleaned all connections from the coil & ing amp both positive and earth. I still have f**k all fire. I follow how to test the coil I think that might be a good next move. I am however more concerned for the 6 volt reading as I have just charged the battery and it's reading 13v on my in car gauge.

[AndyC]

If the coil +ve supply reads materially different to the battery/ alternator/ dash gauge then I'd really suspect that supply wire. Assuming the meter you are reading the voltage with has a high impedance multimeter would) then any current drawn by the coil would still leave the vast majority of the 13v to be seen there. 6v indicates almost the same resistance in the wire to the coil as there is in the coil itself, that's not good.

Damaged dissy to amplifier (that's where those rubber coated wires go once they reach the joint block) wire is a concern. I had one of my cars stranded 1/2 mile form home for several days trying to establish why it conked out only to find the wire had broken internally and had been making contact up until I turned right to go over the bridge, the wire moved and conked out. If you find a good +12v doesn't sort this and the coil itself is good then, assuming you don't have a module tester (mine is out on loan to somebody in Harlow) check for a continuous circuit through that pick-up circuit using a multimeter, and check it doesn't short to earth.

[Benjamin1983]

I have tested live to the coil with it wired out so I can not be loosing voltage to the coil (though I thought it was only current I would have lost). May be interesting to try another earth somewhere in the engine bay as is it not likely if not so more likely that is a bad earth??

[excel tel]

Hi Ben.
Been here myself,not got too much to add,if you follow what Andyc is saying you wont go far wrong.
Have you got any spark at all now?
Start with power to coil-have you got 12v.
Good earth to black ignition module box on inner wing.
Try rewiring two wires from dissy to black box.
once rewired if you place a meter set to ohms across two wires leading to dissy and crank engine you should get a pulse,now this should check the pick up inside the dissy,this was faulty on mine.managed to buy this as a spare part online somewhere for £40.00,just cant remember company name now sorry.
Modules can be tested,i live in Norwich and my local motor factor wilco tested mine for me.
Best of luck,keep trying you will find it.
2.42am thats the sort of time i left my garage when i had same problems.

Cheers Terry.

[AndyC]

Re the earth. Yes use a good earth point, you could assume the engine to be a good earth point but you could be wrong, ideally use something bolted to the chassis.

With a wire break you would have a resistance much greater than normal, this would reduce the current flow for a given potential difference across the length of the wire, but if you were to run an item such as a lamp, coil etc you'd see the potential at the item as being quite a bit lower than with a good supply wire.

Have you now established that given a manual break in the earth to the coil you can actually get a spark?

[Benjamin1983]

I have now replaced the coil for a new one and still have no spark. Anywhere??

[johnthebass]

In the bottom of the dissy lives the "reluctor" this is the pick-up that sends pulses to the ignition amplifier. If it has shifted there is a possibility that the two wires off it have frayed against the body of the dissy causing a failure. Have you checked it? This was the root to a problem I experienced last year after changing plug leads, the coil, the ignition amplifier etc... most frustrating.
Regards John.

[AndyC]

I have now replaced the coil for a new one and still have no spark. Anywhere??

Do you mean even manually controlling an earth with a good +12v you cannot get a spark from the coil?

[Benjamin1983]

I have not attempted this will need to wait until I next take a day off. I just thought in light of the fact the coil is now new the problem is in my eyes unlikely to be the coil itself.

[Benjamin1983]

In the bottom of the dissy lives the "reluctor" this is the pick-up that sends pulses to the ignition amplifier. If it has shifted there is a possibility that the two wires off it have frayed against the body of the dissy causing a failure. Have you checked it? This was the root to a problem I experienced last year after changing plug leads, the coil, the ignition amplifier etc... most frustrating.
Regards John.

I have removed the dizzy I can only remember there being two wires from it both of which were good!