spark occuring 2.5 msec after coil primary grounded?

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hillp
OneWave
OneWave
Posts: 43
Joined: Wed Feb 11, 2004 11:04 pm

spark occuring 2.5 msec after coil primary grounded?

Post by hillp »

Troubleshooting an HC emissions failure, slightly rough idle on a distributor ignition system, 94 Chevy Suburban 5.7 liter. There's an electronic ignition module that fires the coil. It was replaced a few weeks ago along with the coil, plug wires, and plugs; the old one was misfiring horribly. Pickup coil's never been changed in 360K miles. The dwell period before the spark occurs seems to be divided into 2 sections. The first section looks like the one I expect, but there's only a slight blip when the primary is grounded, and then it takes another 2.5 msec or so before the spark actually fires. Seems to me that the spark should have occurred as soon as the primary was grounded. ??
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pri and sec.psdata
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Fat Freddy
TwoWaves
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Re: spark occuring 2.5 msec after coil primary grounded?

Post by Fat Freddy »

Chuck on the Amp clamp. I think you will find it's going into current control.
It's not fully switched off.
Couldn't help it.
Couldn't help it.

hillp
OneWave
OneWave
Posts: 43
Joined: Wed Feb 11, 2004 11:04 pm

Re: spark occuring 2.5 msec after coil primary grounded?

Post by hillp »

Yes, Fat Freddy, that seems to be it. Thanks.

Do you know what the periodic current events are (green trace) that seem to be occurring during the coil's quiet time?
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ignition current dips.pdf
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