Vitesse Mk2 - No Spark

[Paul H]

Hi Dave , you mentioned the ignition cable was linked to negative side and no difference. Out of interest are you running points or electronic ignition. Leaving the ignition on for a period of time will heat up the coil 

Paul 

[daverclasper]

I think!, at the time it was points.

Dave

[Pete Lewis]

It will only heat the coil  more than normal if the ignition is left on with the points closed  and knowone  is going to check that  every time they stop ...are they ???

Running a coil with the polarity reversed does give very low HT and overheat, the car stops you get out swear a bit kick the tyres and it restarts only to stop again after a period .  Used to be a common problem in the old days

Hence later some have male female terminals to avoid this 

Pete

[NonMember]

Technically, swapping the coil LT terminals doesn't really change the HT voltage very much, what it does is reverse the polarity of the neutron flow spark. This will make the spark weaker. The reason is a little involved:

Sparks occur due to a cascade release of electrons from the atoms in a gas. The cascade occurs because a fast moving electron can hit an atom and strip off one or two of that atom's electrons, but atoms are small targets so not all of them hit. So to get this to happen you want plenty of electrons at the start. Now the electrons are released from an electrode because of a combination of electric field and heat. The electric field must be positive relative to the electrode, because electrons are negatively charged and therefore attracted off the metal be positive field. The hotter an electrode is, the more easily it can emit electrons. So the correct way to wire a coil is such that the centre (small) electrode gets -ve HT, because it's the one that gets hot and emits electrons easily. If you wire it backwards, you're forcing the ground electrode to emit electrons, and since that's bigger and connected to the block, it tends to be colder.

(with apologies for the momentary Jon Pertwee channelling)

[Pete Lewis]

Thats cleared it up,  I will stick with if its wrong you , will stop   Ha !!

Etep 

[JohnD]

Well done, Paul! 

 

[Pete Lewis]

Many have made the mistake with  pionts by fitting the leads on top, of the  plastic insulator  bush so direct earth and not

underneath it   and .......insulated

Theres pleanty of Tee shirts for that  one  

Is that all that happended here ??

[dave.vitesse]

As an aside, using a bulb to test when the point open and close will give a more accurate result than using a multi-meter. This is because the switching action at the point requires a current for at least 500ma (0.5A) to work correctly. A multi-meter uses a very low current and does not provide a wetting current for the point contacts. Also the low current can go the other way and indicate a brake and make that are earlier that in the true, normal current, case.

Dave