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Improvised oscilloscope probe for Automotive ignition analysis.
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Jim-0000:

--- Quote from: floobydust on January 04, 2019, 05:35:00 pm ---The coil primary waveform is also very useful, it's how modern ECU's do real-time misfire and ignition fault detection.
Electronic ignition clamps the primary voltage to just under 400V, so max. output voltage is limited compared to points......
--- End quote ---

Yes, I understand that. When we do receive the portable scope I have coming, we can check the primary.


--- Quote ---There's two grounds in a car. One high-current ground is from engine block to battery, and the second smaller ground is from the engine block or battery to the car body/chassis. This is for the in-car loads like fuel pump, ignition, lights etc. A common mistake is forgetting the car body ground which the ignition module may not have been grounded to the block. The firewall is no good unless you have the ground strap from block to body. You can't rely on current flow through motor mounts and U-joints etc.....
--- End quote ---

I insisted that they fit another ground wire from the back of the block to the firewall. Unfortunately, that made no difference to the fault.


--- Quote ---Flipping the carb around, it would mean poor mixing in the intake manifold? I don't see a single carb used on the Holden hi-perf mods.......


--- End quote ---
Yes, that is what we conclude. This engine was first fitted with triple SU carburettors.They were removed and changed in one of the many attempts at eliminating this fault. 

--- Quote ---If possible you can fit an O2 sensor and see each cylinder firing lean/rich to check balance. Maybe joe has tried this.
Otherwise you'll blame the ignition system when nothing is wrong with it.

--- End quote ---

That would be good. I will see if they can oganise one.

I should add that when they (the owner and his brother) tested the car on the track last weekend, they reported that it was cross firing. That is, it was backfiring out the exhaust every now and then. That suggests to me a major distributor problem.
This engine is running on Methanol currently. Several fuels have been run in it previously.
Johnny10:
https://www.ebay.com/itm/US-POST-HANTEK-HT25-High-Voltage-OscilloScope-Secondary-Ignition-Automotiv-Probe/302674748580?epid=1061469482&hash=item4678d224a4:g:aHwAAOSwLg5bWELG:rk:1:pf:0

Why improvise?
Jim-0000:

--- Quote from: Johnny10 on January 04, 2019, 07:58:47 pm ---https://www.ebay.com/itm/US-POST-HANTEK-HT25-High-Voltage-OscilloScope-Secondary-Ignition-Automotiv-Probe/302674748580?epid=1061469482&hash=item4678d224a4:g:aHwAAOSwLg5bWELG:rk:1:pf:0

Why improvise?

--- End quote ---

That is just what I was thinking while looking for Coax cable. Good point!
Thanks.
Johnny10:
Which scope did you buy?

I started with the Rigol 1054Z

Worked well because I could roll back the display while learning to find the signals.

A Picoscope or a Fluke 199 oscilloscope would work.
The picoscope will come with automotive software for free.
Jim-0000:

--- Quote from: Johnny10 on January 04, 2019, 09:40:27 pm ---Which scope did you buy?
............................

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I ordered this little one for my low voltage radio control model aircraft application - before I got involved in assisting the owner of the problem stock car and his brother who is also assisting. This has been highly recommended for my uses:

https://www.banggood.com/Original-JYE-Tech-Assembled-DSO-SHELL-DSO150-Digital-Oscilloscope-Module-9V-p-1211151.html?rmmds=myorder&cur_warehouse=CN

I am beginning to realise it will be useless for automotive high tension application. Also, could damage it first time used as such.
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