Waveform

Simon Diagnostician Clevedon, United Kingdom Posted   Latest   Edited  

This is a relative compression of a diesel engine with a diesel Injector trace "Injector noise" Does anyone know how the red trace (diesel injector noise) is attained ???.

TIA

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Darren Owner/Technician
Bonner Springs, Kansas
Darren
 

I use an amp clamp to get my injector trace,use wiring diagram to find which wire is needed to put the clamp around.

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Simon Diagnostician
Clevedon, United Kingdom
Simon
 

Yes Darren that's how I normally do it but this image is a voltage reference and is very low but apparently only picking up injector noise, I just can't figure out how .

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Jess Diagnostician
Windsor, Wisconsin
Jess
 

On a mechanical diesel I have used clamp which goes around fuel line. Used for injection timing with timing light. Problem is with fuel going through line engine will start normally. So after relative compression without sync. I normally pull one injector and use pressure transducer. It gives me sync and reference pressure. Have had couple large diesels. Where relative compression was even but

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Darren Owner/Technician
Bonner Springs, Kansas
Darren
 

That was a great webinar, can be found on youtube under Pico Automotive

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Simon Diagnostician
Clevedon, United Kingdom
Simon
 

I have seen this video very helpful but I'm still after how to attain the red trace in the picture which is a low voltage reading measuring "injector noise " I think the idea behind this method is for quickness and speed etc.

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Simon Diagnostician
Clevedon, United Kingdom
Simon
 

It is an electronic Injector engine

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Marlin Technician
Estacada, Oregon
Marlin
 

If it has piezo-actuated injectors, that may come from the injector circuit. I never though to try it, but it would make sense that the piezo stack would produce a tiny voltage due to vibration from the compression below the injector. I think that it must be extremely small, however, and may be difficult to differentiate from other sources.

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Simon Diagnostician
Clevedon, United Kingdom
Simon
   

So how would you measure it ?? Because Injector signal voltage be present .

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Marlin Technician
Estacada, Oregon
Marlin
 

What do you mean? Your statement is incomplete.

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Simon Diagnostician
Clevedon, United Kingdom
Simon
 

How can you measure injector noise without actually measuring the injector signal .

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Marlin Technician
Estacada, Oregon
Marlin
 

This would be what is produced by the injector, not anything fed to the injector. The injector probably would need to be disconnected. You cannot (typically) perform a relative compression test while commanding the injectors, because the engine would start.

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Simon Diagnostician
Clevedon, United Kingdom
Simon
 

Thank you that makes sense now.

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Robert Engineer
Durham, North Carolina
Robert
 

May already have been mentioned above but that looks like a knock sensor waveform. if the motor has it that is probably what you are looking at. If it is Piezo feedback from the injector stack itself that would be pretty amazing if out on the market already.

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Jess Diagnostician
Windsor, Wisconsin
Jess
 

First look sensors use piezo to create wave form. So it may be possible. Will try to ask our engineers Monday. If they have seen this feedback from testing. Or if they think the internals would block seeing the feedback with injector disconnected from circuit. I don't normally connect to injectors for voltage and go by current more. Some scopes can only handle so much spike voltage.

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Simon Diagnostician
Clevedon, United Kingdom
Simon
 

But it's a injector sync in the image so how would feedback from the knock identify which injector I am looking at ?

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Jess Diagnostician
Windsor, Wisconsin
Jess
 

The hook ups and vehicle/engine are not described. One other possibility is the high pressure fuel pump was disabled and the sync is injector current for #1cylinder. Like a piezo injector may pulsed. I would consider this not ideal for the injectors. But, may describe screenshot shown. The piezo part of the injector is not directly connected to pintle. It controls a smaller chamber which uses

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Marlin Technician
Estacada, Oregon
Marlin
 

Yes, I hope no one is suggesting injector electrical operation w/o fuel. I also know that the stack is not directly connected to the pintle; I addressed this above. The spell-checker doesn't like "pintle". Hmm.

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony
   

Hi Simon: I could be wrong but it appears to be ground. It looks like someone turned on Channel B for no particular purpose. HTH, Guido

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Daryll Diagnostician
Seymour, Tennessee
Daryll
 

You’ve misnumbered the cylinders. I assume you’re working on a 4 cylinder inline. In that case, you’re taller humps would be (just assuming that you had channel 2, red, connectwd to the #1 injector) 1 & 4, smaller humps are 3 & 2. Not where you jave 3 & 2 right now. Appears that you have a blown head gasket between the middle cylinders

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Simon Diagnostician
Clevedon, United Kingdom
Simon
 

Thanks for all the replys... just to confirm I DIDN'T take the capture I am NOT working on the vehicle I believe it's a 2017 Ford transit van maybe 2.0 / 2.4 /2.2 tdci common rail diesel engine but the person that captured the event wont say how they got it... all I know is that the red trace is injector noise and its simple set up to obtain.

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony
 

Hi Simon: Your response gave me impetus to look a l'il deeper into this. Take a look at around the 35 minute mark and see if this is what you should be looking at. If so, then Channel B on your attachment should've been set to Amps and not Volts. youtube​.​com/watch?feature… (Note: I flat-rated the video.) HTH, Guido

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Simon Diagnostician
Clevedon, United Kingdom
Simon
 

Ok so I have since found out how the red trace was obtained and it was this::: disconnect injector plug and install a test bulb and then put a test lead imbetween the twisted pair of wires which will produce some emf and enough for a sync.

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