355 What's wrong with this injector waveform ?

And, yes, I know, all the injectors are "good".

Have you bothered to do a simple impedance check of the injectors? Are they all relatively the same?

 

Very interesting find. The 355 injectors should have 15+ Ohm resistance. This is the info I found:
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Does the bad waveform have a higher voltage before the ECU triggers the injector?


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Or is the signal not zeroed?

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Is the vertical scale the same?

What is the probe attached to? The ECU pin (backprobing the ECU connector)?

 

This is the way I see it. When the driver is open, Vss appears on the scope. When the driver closes you see ground potential. The absence of the flyback spike indicats that there is no reactive load which would indicate the injector is shorted or there is a very low resistance in parallel with the injector coil.

One other possibility would be a very high resistance on the supply side (Vss side) limiting current to the injector.

As Ian pointed out, it would be nice to know if the voltage scales are the same for the good and bad injector because if you aren't seeing a true ground on the driver side then it could indicated the driver has some parasitic resistance when close which would also limit the current to the injector.

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Ok so I frigged up 1 of the pigtails I made so this happened to be the one I used for cylinder 2 and 3
After fixing the crimped wire and retesting as per diagnostic sheet 11(which was how I found it) all injectors appear too be working
I will get traces of them tomorrow and post
So it seems I have not found the problem again since when the injectors were plugged directly and not into the pig tails for testing on the scope they would have been working it seems.
Need to confirm this obviously tomorrow

 

The only time it doesn’t matter which wire is when you are looking at AMPs with either a amp clamp or inline meter

When checking voltage with a scope you need the red probe on the wire that is being switch on/off and black probe to ground if the signal is a grounding circuit if switch power then reverse the probes but either way still need on the wire that switches


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So all my tests were with the probes hooked up backwards according to the people in the know.
I will attach a few scans from today but will reverse the probes and put all clamps to common ground at the back tomorrowThis scan has probes that reference each cylinder

Here are some of the scans from today and a video but the probes were on power and the alligator clips were to each injector ground
The scan today show it in the firing order 1 3 4 2


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Here is a short video with the 1 3 4 2 firing order going down from top as above picture

 

I don’t know why the movie did not load correctly

 

I would swap the injectors to different cylinders and see if the problem stays with the same cylinders or moves with the injectors.

 

all the scales for voltage was the same I just did not put it on zero the same

remember though it was my bad pigtail causing this issue as my previous posts show the same

 

Image Unavailable, Please Login The snapshot above was during a video so that is why cylinder 1 happens to not be lined up with 0 degrees this is closer

 

The scales were the same but I had a poor connection or actually no connection on a crimp

 

It was a bad connection on a pigtail being used inline with the injector so I could hook the scope up without back probing

 

Grant asked me to post this video of his injector pulses. Have a look. All well and good.

 

All the waveforms in this pic look uniform and good still not sure about the voltage ranging of your scope

I can see you are trigging your trace on channel 1 at 280.0 mv with a forward slope and the update rate is 20ms horizontally across the screen meaning you will only see a trace after the voltage rises about that threshold if you are not on auto range (which you should not be)

The injectors should open when the intake valve is at or close too full open so what is the degree scale on the screen referencing ???

What is the problem with the engine is it missing or running rough ???





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Ok will try that but will be a few days sorry for the delay busy at work again due to ‘winters coming” ha ha

 

I do have this one
does it show scale or width of pulse/?

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The increments in your last photo seem to show microseconds. That's ridiculously short for a pulse. What cylinder was that? Your photo in post #37 shows relatively normal scales/pulse widths.

 

I think that’s correct but would the 10x on the probe mean it’s the same as 10 micro seconds?
It is at idle
It’s also only 1.5 dots roughly in post 37 and its 22 dots on this scale
I think you would read it off of the notes but not sure what they mean
But it says
R1-width is 112ms not sure what most of that righting at the bottom means

I did not know how to save it so it was saved as a reference waveform ie R1 with a description of
Cylinder 4
Then I zoomed in after so it probably just means that to make it that large 1 pushed the ms button to go from 200ms down to 1 micro second so it would get bigger
Not even sure if that makes sense but I think that is what I did
I used it as a zoom basically to see the shape

 

Where is the "10x" shown? It sounds more like a vertical scale, not horizontal. i.e. voltage

Even at 10microseconds per (horizontal) increment, the pulse width in that photo is only about 45 microseconds. Typical vehicle pulse widths should be around 2500 to 3500 microseconds at idle. Something weird is going on with your measurements.

 

It does on one display, but what's happening on the second pic?

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Should that read 1 ms, not 1µs?

 

The pic on the right with (1 ms) should mean that each division across the screen is 1 ms so if I’m reading it right your ECM is supplying ground to the injector for 5.1/2 ms which for idle is ok in close loop

What brand and model is the scope


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