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MG MGB Technical - no spark

I am totally lost as what to do next
I have a 74 roadster and i can't get a spark at the plugs or points.
Power is reaching the points everything seems to be ok but no spark.
It may be quite simple but I just can't see the problem.
Antone got any good ideas???
gus

Gus. Did someone recently replace the points? These points are an older design and you do not simply attach the wire coming from the coil to the points as you might on modern (and most not so modern) points. The wire to the points will have a ring connector and it must make contact with the spring arm, while being insulated from the center post (the one the nut screws onto) by the white plastic spacer. If you simply attach the wire to the points and fastern down the nut, the current grounds out immediately, hence no spark as there is no make/break circuit. If you have good power to the points, you either have a direct ground (as above), the power is not grounding through the points (bad baseplate ground wire/bad dizzy to engine grounding) or a bad secondary winding of the coil. Probablility is in that order. Les
Les Bengtson

With the ignition on and points open you should see 12v at the coil -ve (white/black to the points and tach) and the points moving contact. If you see a ground then the points/condenser/wire is grounding somewhere, possibly due to incorrect assembly as per Les.

With them closed you should see a ground at that coil terminal. If you don't then the points wire could be open circuit, the conductor can break inside the insulation.

If they are OK then there is something else wrong like open-circuit condenser (causes weak sparking at the plugs but major arcing at the points) or bad coil. With a good condenser you will still get some sparking at the points.
Paul Hunt

Thanks to Les and Paul I will try out the ideas once the wind calms down Paul will understand more than Les.
I will let you know if it works in the next day or two.
Thanks again
Gus
Gus

Hi Paul and Les

No joy
I am getting a very weak yellow coloured spark at the points just as the engine stops winding over.
Any other ideas?

Gus
Gus

Gus. Go to my website, http://www.custompistols.com and click on MG articles. One of them deals with troubleshooting the ignition system. It should help you diagnose the problem. E-mail me thorough the website if you have any questions or problems. Les
Les Bengtson

A weak yellow spark that barely jumps a plug gap indicates an open-circuit or diconnected condenser. Should be a blue spark that you can draw out to at least 1/2".

However if you say that you only get that spark just as you stop cranking then maybe your ignition switch is faulty and disconnecting the power from the white and hence the coil while you are cranking. Put a voltmeter on the coil +ve and check you have 12v with the ignition on and about 10v while cranking.
Paul Hunt

This thread was discussed between 27/01/2002 and 31/01/2002

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