Taffy TR Man Posted July 10, 2011 Report Share Posted July 10, 2011 (edited) Any help very welcome please... In tracking down my ongoing no spark issue I have reverted to points and condenser... All wired up.. 12v live to +ve coil Dizzy to -ve Good earth to base plate. Connected battery and put ignition on... smoke starts snaking out of the dizzy cap... With cap off you can clearly see the red points post melting... With just the 12v feed to the +ve side of the coil and nothing else the negative side of the coil has 12v also.... Edited July 10, 2011 by Taffy TR Man Quote Link to post Share on other sites
TRTerry Posted July 10, 2011 Report Share Posted July 10, 2011 I guess you have checked the coil for a short, or substituted it with another coil. The dissy works by a rotation creating pulses ( contact breaker) at 12 volts that the primary winding of the coil sees. This pulse excites the secondary winding of the coil which is wound to a different ratio so generating a much higher voltage, sufficient to jump the gap at the spark plug. Do the contact breakers open and close on engine rotation? The fact that ignition amplifiers which don't use contact breakers also burned out suggest to me that somehow the dissy is stuck in an 'on' position. What should be a brief pulse which is effectively a deliberately created short, is now a long one with all the power of the battery to deal with. The fact the fault seems consistent across two different spark creating techniques would be my starting point. Quote Link to post Share on other sites
johnny250 Posted July 10, 2011 Report Share Posted July 10, 2011 Any help very welcome please... In tracking down my ongoing no spark issue I have reverted to points and condenser... All wired up.. 12v live to +ve coil Dizzy to -ve Good earth to base plate. Connected battery and put ignition on... smoke starts snaking out of the dizzy cap... With cap off you can clearly see the red points post melting... With just the 12v feed to the +ve side of the coil and nothing else the negative side of the coil has 12v also.... I have not seen your previous posts Taffy, but with no connection to the negative side of the coil you will read +12Volts as no current will flow to drop any voltage. If you mean the red plastic insulating heel that opens the points by rotation of the cam, is melting.... then it must be conductive....or the cam lobe is very hot. john Quote Link to post Share on other sites
bigfella Posted July 10, 2011 Report Share Posted July 10, 2011 Hi Just a thought - have you got the points wired up so as to cause a short i.e. not got the insulation part in the right place on the terminal post so as to cause the wires to short out. Easily done - I managed it on an old mk2 Jag a while back witrh smoking wires as a result ! Quote Link to post Share on other sites
peejay4A Posted July 10, 2011 Report Share Posted July 10, 2011 I'm with Terry. It sounds very much as though there is a fault with the coil - internal short cct or similar. Check the resistance from + to -, it should be a few ohms. Quote Link to post Share on other sites
Taffy TR Man Posted July 10, 2011 Author Report Share Posted July 10, 2011 Woohoo! Changed coil to my old one and changed the condenser - started on the button with no problems. From that point I am relieved, quite why my 'new' coil tested fine and the fact I tried both old and new coils with both electronic ignitions and still got no spark makes no sense ! Anyway - we have engine noises ! Thanks for your help as ever... Geoff Quote Link to post Share on other sites
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