Weak Spark?

[fiasco]

This is a situation I've been dealing with ever since the new engine went in March.

Things started out fine, but as time passed, performance gradually degraded. I was getting backfire in the exhaust and sputtering, and no power when starting out from a stop. Eventually the car died completely and wouldn't start. With some help, I checked lots of things - wires, points, coil (replaced the coil). I was getting current through all the systems but no spark. Alvon suggested I replace the ignition condensers (2 because of dual points), which I did, and all problems immediately went away. Everything ran strong, and I had great power and acceleration from stop.

Then, gradually (but faster than the time before), all symptoms came back. What it has previously taken 3 months, now took 2 months. This time I replaced the condensers before getting all the way to death, and when replaced the symptoms mostly went away, but I didn't get back to as good a condition as I did the first time I replaced the condensers.

So the second replacement was about 6 weeks ago, and now I am back to very poor performance again. Sputtering and backfire when starting from a stop, and very poor power and acceleration.

I'm thinking that my performance and backfire problems are due to weak spark. Not all the fuel is getting burned, so I'm getting backfire in the exhaust, and power/acceleration suffers as well. Does that make sense, or am I looking in the wrong direction?

So who has ideas for me? What would cause degradation of the condensers? The coil is new in June, the wires and plugs are new in March.

Thanks all!
-- se

[ventura ace]

Here's an article with a lot of useful information: http://mgaguru.com/mgtech/ignition/ig106.htm

It gives a good step-by-step list of things to check when troubleshooting a weak spark.

Alvon

[fiatS2000]

convert it to electronic ignition. All you need is the complete distributor, coil and module from a 2L spider.

[So Cal Mark]

so you haven't actually verified weak spark?

[Schnauzer]

Make certain that you have the correct coil and/or the correct ballast resistor for that coil. Some coils have internal resistors and some do not. If the proper voltages are not supplied you may be arching and burning the points. You can test your coils primary and secondary windings with an Ohm meter. Should be approximately 2.7 to 3 ohms on primary and 7000 - 9000 on the secondary. You can also check voltage at the points which should be about 8vdc. The numbers I am giving you are off the top of my head so seek better advice if you see descrepancies. Check to see if you are burning the points. You can also go to a single point set up to eliminate the posibility of the problem being related to when the timing change over takes place. Again take my comments as sincere but suspect as I am not the expert here.

Jim

[So Cal Mark]

coil saturation is determined by dwell, so if the point gap isn't proper spark voltage will suffer

[majicwrench]

As Mark mentioned, you need to verify weak spark, not just assume weak spark. Grab an old plug and open the gap up to .060 or so, stick it in a plug wire, and start engine. Should have a scary looking spark jumping the gap, zap-zap-zap.
Keith