Scope: saturation injectors and full ground?

- L
- LanceM
  
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posted
20 years ago

Fri, Oct 17, 2003 1:59 PM

High impedance, PFI pintle-style saturation injectors

I've seen two waveform references: the first one, which is what I'm seeing on my scope, shows that the (negatively controlled) "on" pulse doesn't go to full ground, but rather just down to ~1.5 V (this seems to imply a Peak and Hold, rather than a saturation injector [or maybe that's more of a distinction of event duration]?)

The second waveform ref sample shows the injector opening with a full ground.

Are both possibly correct, and just due to slightly different injectors and/or ECMs?

Thank you, Lance

- N
- Neil Nelson
  
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posted
20 years ago

Fri, Oct 17, 2003 2:42 PM

On a peak and hold, you'd probably see the signal go to full ground first, then step up to the 1.5 volt value.

As a general rule, peak-hold injectors will be low impedance and typically used in TBI systems, full saturation injectors will be higher impedance and used in PFI type systems. (it's all about current control)

Yes.

Unfortuneately, not everything can be cataloged, not everything is going to have printed known good examples, which is why familiarization with test equipment and its results is best done ahead of time on stuff that you know is working correctly. (doesn't help your situation much 8-(

Many imports, especially the older ones used a ballast resistor(s) in series in the injector circuit, perhaps this is the result of what you're seeing with your 1.5 volt ground anomoly? (I don't see the injector circuit shown on the EZK URL)

- L
- LanceM
  
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posted
20 years ago

Fri, Oct 17, 2003 5:57 PM

There are a few minor differences, but this is very similar to my fuel mgmt system

http://216.78.172.20/electrical_system_folder/lh24wiringnfmp.htm One would think, with that simple of fuel and ignition systems, I'd be able to figure out what's wrong!

No ballast, so I'll explore the 'ground' a bit more, but understand it may be normal

The scope has been an invaluable supplement to the DMM in V-dropping everything, checking individual components, and much more (plus they're just cool)