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1999 Mitsubishi Galant, 3.0L - Random High spark kv

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6 years 1 month ago #18063 by jsvets2326
This weekend I tested a intermittent no start. With my amp clamp, testing the primary current ramp I found a shorted coil, the ramp had a big jump up at the start instead of the normal linear incline (textbook shorted coil). Also the secondary spark line was at almost zero kV, but the firing line was at 20-30kV, seemed weird to have such a high firing kV but such low spark kV, can anyone explain this. It had me confused about a bad coil with such high firing kV. Also on the primary voltage there wasn't any oscillations at the end of the burn, and instead of the voltage dropping to zero with oscillations it just VERY gradually sloped down to zero, which I also believe is due to the bad coil but I don't understand why the voltage gradually slopes to zero instead of dropping straight down almost like the voltage is slowly leaking out.

And for my main question after replacing coil car runs great but firing kV is still close to 30kV spark kV is usually around 3kV which I believe is the only thing that makes since, but randomly the spark kV will increase to 10kV, so I have this fluxuation between let's say 5 good sparks at 3kV and then one spark at 10kV, then repeat. The one real question I have is, does anyone know what would cause a random increase in spark line kV, from 3 to 10 randomly. I should have zoomed out to see if it was systematic but I didn't so could anyone give me a general reason why spark kV will run around 3kV and every so often jump up to 10 for one spark and then drop right back down to 3. Sorry I didn't get any waveforms still little new at all this, but I will do better next time.

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6 years 1 month ago #18064 by jsvets2326
I feel like I'm doing the customer a disservice as with the kV between 20-30 I feel like to coil is going to short in a year or so. I also forgot to add vehicle info this is a 1999 Mitsubishi Galant, 3.0L, the coil is in the distributor, do these have higher than normal firing kVs.

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6 years 1 month ago #18067 by Dylan
Moved your topic over here ;)

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6 years 1 month ago - 6 years 1 month ago #18068 by Chad
Firing KV is the amount of voltage required to overcome all the air gaps/resistance in the secondary circuit. (Plug wire resistance, cap/rotor, spark plug air gap.) The higher the resistance, the move KV required to jump the gap. Spark KV is the amount of voltage to maintain the arc across the gap. When this value is unstable, it is an indication of varying resistance inside the spark plug gap. (varying fuel, compression)

"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."

I have learned more by being wrong, than I have by being right. :-)
Last edit: 6 years 1 month ago by Chad.

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6 years 1 month ago #18073 by Andy.MacFadyen
I don't see any 3litre Galants what is the ignition set up -- one coil per cylinder or shared coil wasted spark ? Lean mixture gives high KV but did you also replace the spark plug ?

" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)



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6 years 1 month ago #18075 by Chad

Andy.MacFadyen wrote: what is the ignition set up -- one coil per cylinder or shared coil wasted spark ?


jsvets2326 wrote: the coil is in the distributor


"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."

I have learned more by being wrong, than I have by being right. :-)

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6 years 1 month ago #18076 by Chad

"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."

I have learned more by being wrong, than I have by being right. :-)
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6 years 1 month ago #18080 by Andy.MacFadyen
A distributor throws the dice again on possible causes, the distributor shaft bearing wears causing the spark gap distributor to change as the shaft wobbles about, the rotor arm itself can have issues due to erosion or arcing to ground or a problem with the suppressor resistor built into the rotor arm. Then of course with a distributor you have spark plug wires which are subject to heat vibration have opens and shorts.

" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)



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