Injector waveforms. - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 03-30-2007, 06:03 PM   #1
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Default Injector waveforms.

So... I'm not liking my injectors right this second and I threw my o-scope on one. I'm getting what I consider odd readings. Anybody ever done this or have more experience?

Here'* my scope:
BK Precision 2160 60MHz Oscilloscope
Here'* my settings:
Coupling: HF
Sweep Mode: Main
Time/Div: 0.1mS
Delay Time Base: 0.1mS
Volt/Div: 0.5V DC

The best that I can think of is that I'm seeing the spike after the solenoid closes, but to check this I moved the TPS up enough to show me two pulses at the same time and there is no drop. Just a spike and ripple. Anybody got any ideas?

I have my lead grounded to the fuel rail and sensing the BLK wire. PNK/BLK is power and BLK is ground (to the ECM) for #1.
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Old 03-30-2007, 06:15 PM   #2
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Here'* a sample:


I'm not seeing the drop, just the spike and a very dirty ripple afterwards.
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Old 03-30-2007, 07:13 PM   #3
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Heh, Ground to the block BTW. I've got 2.4mS IPW @ 725 RPM. I saw it jump to ~6mS @ 20% TPS blip.
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Old 03-30-2007, 08:18 PM   #4
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So... Anybody got any idea of what I could sync to? It'* a little hard to interpret this with it sliding all over the screen based on timing.
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Old 03-30-2007, 09:12 PM   #5
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Well, 1.8 to 1.9ms at idle and 8-9ms at 20% TPS. I can't see over that.
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Old 03-30-2007, 11:58 PM   #6
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You could try an inductive pickup from one of the spark plug wires as a trigger. From your waveform, it looks to me as if you have the PCM giving ground from 0 to almost 2 on your graph. Then the ground is removed, and as the solenoid deactivates, I'd expect to see a pulse as you have there, as well as some ringing (ripples) as the coil de-energizes.
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Old 03-31-2007, 12:32 AM   #7
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The "I put everything away for the night" update.

I finally got it to trigger correctly using the feature built in, my trigger level **** is starting to have problems. Pulling it out makes it work.

My IPW with the idle oscillating from 725 to 775RPM are as follows:
1 3.4 - 3.6ms
2 3.4 - 3.6ms
3 3.6 - 3.8ms
4 3.6 - 3.8ms
5 3.4 - 3.6ms
6 3.6 - 3.8ms

Now to find out how much fuel that equates to and how much the engine is actually getting. I need to find flow numbers for my injectors at some point.

Archon, Sorry for not specifying earlier but the above graph is from somewhere out on the internet, stolen without permission. It does show what would be a perfect graph for my system (and yours too i suspect) but it'* not mine, or anywhere close to what mine shows.

Mine shows the 12V potential on the line, then a nice clean drop as the injector pulls. I've got a ~60V inductance spike that comes down very dirty. I'm not sure why it'* so knarly looking but I should get the answer out of one of these books at some point.

GM P/N: 17121296
Ac-Delco: 217-307
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