In cylinder pressure testing

Ryan Owner/Technician New Jersey Posted   Latest  

Good evening all

i have a four cylinder Nissan That got towed into the shop for a no start. getting Compression out of radiator. Car is old and customer declined work. 

we decided to break out the transducer and do a in cylinder cranking test as we are really just learning the ins and outs of this testing procedure and we had some free time . the problem is on all four cylinders I Do not see a intake vacuum pocket . Am I doing something wrong in setup? 

Thank you all

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Dmitriy Analyst
Ontario
Dmitriy Default
 

If you are cranking at Wide Open Throttle there can be no vacuum in the intake. Are you cranking at WOT?

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Ryan Owner/Technician
New Jersey
Ryan Default
 

Hey Dmitriy during these test we did not have the throttle Open. The throttle plate was at a idle position. Also , we did not disable fuel now that I am thinking about it . Would that play a factor?

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Daryll Diagnostician
Tennessee
Daryll Default
 

You won’t have much of a vacuum reading at cranking, engine speed is too slow to create a large pressure difference after the throttle plate I would encourage you to learn as much as you can about in-cylinder waveforms and testing, then graduate up to a Pico WPS500 transducer. Will work just fine with your Verus. I use my WPS with my Zeus a lot, love it. I have the SO transducers as well but…

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Ray Diagnostician
Ontario
Ray Default
 

Practice the in cylinder cranking and running compression on a known good engine to learn what good wave forms are supposed to look like.

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Steve Diagnostician
Ohio
Steve Default
 

You will not get a visible vacuum signature at cranking speed. If you are looking for a typical engine running wave form you will not get it in a cranking situation. It also looks to me that your exhaust signature is too rounded at the opening stage which may indicate a valve train problem.

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Ryan Owner/Technician
New Jersey
Ryan Default
 

Got it!! Thank you all ! Very helpful

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Darryl Technician
New York
Darryl Default
 

Snap on transducer kit is not designed for in cylinder psi diagnostics and there tech support doesn’t even acknowledge the issue when calling them . I found it to be waste of money for that purpose

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Ryan Owner/Technician
New Jersey
Ryan Default
 

Interesting ! What problems have you had with snap on pressure transducer that they are not acknowleding ? Same issue I’m seeing ?

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Darryl Technician
New York
Darryl Default
 

Signal quality you can’t see io and ic events

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