secondary ignition analysis

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secondary ignition analysis

Postby antthecat » Fri Mar 23, 2012 10:27 pm

hi all, i have had a merc ml320 in the workshop with a misfire, scanning logged cyl 2 and 5 misfire detected, with the vehicle having plug leads i thought for good practise i wanted to analyse the secondary pick ups, cylinders were rigged up as follows:

cyl 2 blue
cyl 5 red
cyl 1 green (supposed good cylinder)
cyl 4 yellow

i could not pick up anything like what i have seen in the library and my course notes, noted blue and red are different to the other two, i did swap over the coil packs to see if there was any change, no change.

The outcome of the misfire was low compression on cyl 2 and 5, vehicle is off to the breakers i believe.

Just wanted the experts to analyse what i found, am i seeing a poor burn due to low compression or have i rigged the scope wrong.

Ant

merc secondary snippet.psdata
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Re: secondary ignition analysis

Postby Mick » Sat Mar 24, 2012 1:32 pm

Ant

Is this secondary system a coil near plug with 2 plugs per cylinder?
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Re: secondary ignition analysis

Postby antthecat » Sat Mar 24, 2012 2:18 pm

Yep, coil packs on rocker cover and 2 plugs per cylinder, will admit I did only scope the a lead, not the b lead.
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Re: secondary ignition analysis

Postby Mick » Sat Mar 24, 2012 4:00 pm

I thought so,

I will get back to you
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Re: secondary ignition analysis

Postby Mick » Sat Mar 24, 2012 11:40 pm

Hi Ant

I had made some notes and actually posted but withdrew it all because I noticed the firing order does not line up with your first post.

Firing order should be 143625 so that would leave your ChB cyl 2 and ChC cyl 5.

Bank 1 has cylinder 123 and bank 2 has 456.

If this is correct then I will continue.
Last edited by Mick on Sun Mar 25, 2012 11:54 am, edited 1 time in total.
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Re: secondary ignition analysis

Postby antthecat » Sun Mar 25, 2012 9:31 am

Your correct with firing order, I think I made some hash up with the set up, I thought the vehicle had disapeered but it us still in the workshop (customer was meant to pick up vehicle sat morning but was there when i popped in at midday).

I'll get in early Monday morning and rescope secondarys in firing order, will admit I was just concerened with the waveforms not looking like what I've seen before.

Will post a better set up as I think I've got some wires crossed somewhere. Cheers for the help on this thus far.

Ant
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Re: secondary ignition analysis

Postby Mick » Sun Mar 25, 2012 1:36 pm

Ant

Do you think the notes in this gif would represent how you hooked up?

measure average Kv.gif


I find if I take the time to write in the notes section as I am hooking up my leads it helps.
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Re: secondary ignition analysis

Postby antthecat » Sun Mar 25, 2012 10:45 pm

Cheers for showing the notes section, i am so used to relying only on my short term memory for everything and lately it has gone south,, will make solid notes from now on.
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Re: secondary ignition analysis

Postby Mick » Mon Mar 26, 2012 1:26 am

antthecat wrote:Cheers for showing the notes section, i am so used to relying only on my short term memory for everything and lately it has gone south,, will make solid notes from now on.



I like to capture primary Volts on these coil near plugs because burn time is the most important part of the wave.

If you do capture Primary Volts please attach the attenuators on each channel and select the Pico custom probe of it.

This gif shows a fault in the B side of the coil which caused quite the misfire.


Primary Volts.gif
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