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Injector Testing With Secondary Probe

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4 years 5 months ago #34194 by Noah
Thanks to Tyler for giving me the idea to build a secondary probe from an old Honda distributer pick up. B)


While playing around with it, I started to figure that it should be able to detect more than just coil firing. So how cool would it be to walk over to a car with a misfire and touch the coil to verify spark, and then use the same tool to touch the injector and verify operation?

At a 2v scale, 20ms time base I seem to get the cleanest captures. Now to compare to the methods we already have to try and dissect the waveform.
I'm trying to determine if mechanical movement can be inferred from the pattern. I think so, but I'm not there yet.
Let me know what you think.
Is it a viable test?
Am I just being stupid?



"Ground cannot be checked with a 10mm socket"
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4 years 5 months ago - 4 years 5 months ago #34195 by Noah
Here's a capture touching the purge solenoid on my Honda with a voltage trace on the control wire for comparison.


Sorry the forum uploads my pictures sideways and upside-down :(

"Ground cannot be checked with a 10mm socket"
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4 years 5 months ago - 4 years 5 months ago #34197 by Chad
I believe I can see pintle opening.




"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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4 years 5 months ago #34198 by Noah
That's where I was looking also. Guess I need to find a car with a stuck injector now

"Ground cannot be checked with a 10mm socket"

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4 years 5 months ago #34199 by Tyler
I was trying to think of a way to 'stick' an injector? :huh: Like, feed it sandblasting media to keep the pintle from closing. I dunno, just speculating! :silly:

The flexible handle for the probe is inspired, sir. I can see that being easy to get in under Escape intakes and such.
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4 years 5 months ago #34259 by Tutti57
Awesome!
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4 years 5 months ago #34348 by Noah
Here's another one I had a chance to hook up to today.
2006 Cadillac CTS 4.6l
It looks like when the downward slope of the blue trace begins to climb is when the pintle hump is visible in the current ramp.

"Ground cannot be checked with a 10mm socket"
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4 years 5 months ago #34349 by Noah

"Ground cannot be checked with a 10mm socket"
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4 years 5 months ago #34609 by FrugalPrepper
I am wanting to test with a stuck injector as well. I am trying to get these wave forms down. I was considering a trip to the salvage yard for an injector and then a syringe with some Harbor Freight Epoxy. I think I will be picking up a Honda distributor pickup as well now!
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3 years 9 months ago - 3 years 9 months ago #40315 by Noah
This is the build for Andrew.
It's seriously not fancy, so don't be too disappointed.


I deftly extracted, well, more truthfully brutalized an old Civic distributer to get the pick up out of it.
That's the little tid bit in the middle.
It's much larger than that to start. After I harvested it I ground much plastic off it (per Tyler's instruction) to get it down to that little giblet.




For the handle i used the flexible neck from my Astro rechargable light, which was also brutalized in an unrelated event.
I fed an old set of meter leads through the handle and connected them to the leads of the pick up. It was a total shot in the dark as far as determining polarity. I figured if it sucked it could always return to the trash from whence it came.

I wrapped the whole deal in mastic tape which gives it a nice rubberized-ish handle and a not-so-piece-of-crap look.

One lead goes to chassis ground, the other goes to the scope.
Then it's just a matter of fiddling with the scope to get the best pattern.

"Ground cannot be checked with a 10mm socket"
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3 years 9 months ago #40355 by Andy.MacFadyen
Just love it :-) I have always been meaning to see if some sort of ignition probe would work on a disel common rail injector --- might be too much metal for it to work but a pick coil might.

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



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3 years 9 months ago #40357 by Andy.MacFadyen

FrugalPrepper wrote: I am wanting to test with a stuck injector as well. I am trying to get these wave forms down. I was considering a trip to the salvage yard for an injector and then a syringe with some Harbor Freight Epoxy. I think I will be picking up a Honda distributor pickup as well now!


On plastic injectors a tool clip round the body of the injector works as capictive probe, found that out when we were exploring using knock sensors as injector probes --- there is a whole long thread on that. way back in the early days of the forum.

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



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3 years 9 months ago #40361 by Tyler

Andy.MacFadyen wrote: On plastic injectors a tool clip round the body of the injector works as capictive probe, found that out when we were exploring using knock sensors as injector probes --- there is a whole long thread on that. way back in the early days of the forum.


You're talking about this one, right?

www.scannerdanner.com/forum/diagnostic-t...-a-knock-sensor.html

You've got some testing gold in there. B)

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3 years 8 months ago #41145 by al514
Is that what that roundness is on the yellow trace ( 2pics up)? I assume the green trace is a backprobe reading? If this is true, then genius! Next level, another quick test to take a peak at injectors. And if we can learn wave forms under different circumstances, then that's another step up in testing, and it's so basic.
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3 years 8 months ago #41146 by Noah


That one?

Yes, that's a home made secondary ignition probe touching a fuel injector in yellow with the control voltage displayed in green.

Thank you for your interest :)

"Ground cannot be checked with a 10mm socket"
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3 years 8 months ago #41316 by Jonathan Haffer
That’s nice I’m in the process of grinding mine down, it’s a lot to grind

Jonathan Haffer
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3 years 8 months ago #41323 by al514
Does the entire assembly need to be a certain resistance? Or just a coil of wire,and do you use any attenuators ?

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3 years 8 months ago #41327 by Noah

al514 wrote: Does the entire assembly need to be a certain resistance? Or just a coil of wire,and do you use any attenuators ?


I never gave the resistance a thought to tell you the truth.

As far as an attenuator, there's no danger of going over voltage since we're not actually measuring the KV the coil putting out. Instead we're measuring a much smaller voltage that's being produced by the distributer pick up interacting with the magnetic field created by the ignition coil firing.
Kind of like an amp clamp doesn't actually measure amps, but puts out a low voltage proportionate to the current flow in the circuit.

Plus the Snap On Verus scope will handle most of the high voltage produced from things like ignition coil primary voltage spikes without the use of an attenuator, so I don't even own one.

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3 years 8 months ago #41328 by Noah
I will add that there is the potential danger of a secondary voltage (spark) jumping from a plug wire or compromised coil insulation to the scope lead.
That could be bad news.
That's why It's important to clamp one lead of the tool to block ground or chassis ground to minimize that danger.

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3 years 8 months ago #41338 by al514
Well I was just worried about it cause I don't have a high end scope, it does have a 10x1 attenuator on the leads, but I'd love to try this. I'm of the mindset that I'd rather scope something than pulling it apart as you guys are. Still abit new to scoping, so I'm still dealing with the learning curve.
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