912 Ignition Problem

by amna hanif in 912 / 914 Technical Questions 13 years ago

Recently, while troubleshooting the problem of RPM drop of more than 300 during ignition check i came across ignition mate and used it to measure spark voltage and current during engine run. The values of spark voltage @ 3000 RPM were as follows:
cyl 1 Top 7-10 KV
cy1 1 Bot 9-11 KV
cyl 3 Top 8-11 KV
cyl 3 Bot 6-9 KV
cyl 2 Top 12-14 KV
cy1 2 Bot 14 KV
cyl 4 Top 12-14 KV
cyl 4 Bot 12-14 KV

The manual of ignition mate suggests that the spark voltage values of same polarities must be same.
As cyl 1 and 3 have spark of same polarity that suggests their values must be equal.But i am not sure what these KV values suggest regarding the health of ignition system because i do not have a reference value of spark voltage and current.
If i could get the true values for spark current and voltage that would help me to determine the problem further.
P.S What are the ideal values of primary and secondary coil voltage?

Re: 912 Ignition Problem

by mike hallam » 13 years ago

mike hallam

3 40 0

Amna,

I suspect that the voltage seen/measured at a plug varies also with the plug gap. So a closer gap has a smaller path for the spark to jump, thus it's able to jump whiule the source voltage is still rising and damps down any/much further rise.
It might be worth a simple experiment with your magic kit by changing one plug say from 0.7 mm to 0.8 mm [or whatever you fancy trying] ?

mike (England)

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