Hi om new to pico and havent used it much.
I have a car inside and it doesent start, i checked for spark and fuel and last compression. It showed 0 bar needle not even moving on any of the 4.
For fun i decided to hook the 4225 up and do a relative compression check. I was alitle bit confused when it showed all cylinders. Above 80% 92 as lovest if om remember correctly.
Is my gauge lying or is the answer that all cylinders are equaly bad. Can anybody please give dome tips if i can use the pico in any other way to show cylinders pressure. Sorry for the bad language im swedish and fighting bott the language and autocorrect.
Pico diagnosic comp 100% gauve 0bar
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Norrflarkemek
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Re: Pico diagnosic comp 100% gauve 0bar
Post psdata of your captures Cheers Ron W
Re: Pico diagnosic comp 100% gauve 0bar
When all cylinders are equally bad then this will effectively result in similar readings for all cylinders on RC(relative compression) ok 
You may check the current consumption and cranking speed: with zero compression the starter will draw less current than normal and the cranking speed will be higher.than normal. A conventional leak down test may be helpful just to see where the pressure is lost.It might be timing as all cylinders are affected.
You may check the current consumption and cranking speed: with zero compression the starter will draw less current than normal and the cranking speed will be higher.than normal. A conventional leak down test may be helpful just to see where the pressure is lost.It might be timing as all cylinders are affected.-
Norrflarkemek
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- Joined: Wed Dec 29, 2021 10:32 pm
Re: Pico diagnosic comp 100% gauve 0bar
Is this to any help?
this is a cheap car and the owner wont spend the money on it to fix it.
they thougt it was only the fan belt that snapped. i think the fan belt snappet and went in to the timing belt and made it slip. is was pretty happy when i found the 0 compression. i only hocked the Pico up beacuse im planing on trying to learn more aboute it and was a bit confused. actualy im i bit confused of a engine with all cylinders at 0 BAr, but i guess everything can happen.
this is a cheap car and the owner wont spend the money on it to fix it.
they thougt it was only the fan belt that snapped. i think the fan belt snappet and went in to the timing belt and made it slip. is was pretty happy when i found the 0 compression. i only hocked the Pico up beacuse im planing on trying to learn more aboute it and was a bit confused. actualy im i bit confused of a engine with all cylinders at 0 BAr, but i guess everything can happen.
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Steve Smith
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Re: Pico diagnosic comp 100% gauve 0bar
Hello and thank you for the posts
As jueja as mentioned, the confusion has crept in because all cylinders are, or appear to be, equally low (0 Bar)
Relative compression results are calculated by comparing the largest volt drop across the battery (best performing cylinder) against the volt drop acquired from the remaining cylinders
I.e., the remaining cylinders are compared “Relative” to the best performing cylinder
This cycle is repeated for every volt drop event based on the cylinder count value entered into the software
E.g., Entering “4-cylinders” provides the interval over which the 4 volt drop events (for 4-cylinders) are repeatedly analyzed during cranking
In your scenario below, we can see very little volt drop across all cylinders and therefore the comparison suggest that all remaining cylinders are near 100 % of the volt drop detected for the best performing cylinder
What is interesting above is the reported cranking speed which suggests a near “expected” RPM value for a good engine. I would have expected this to be a lot higher with no compression!
RPM is calculated based on the frequency of the signal and the entered cylinder count. The software will identify 2 volt drop events (one crankshaft revolution) calculate the time taken for these events to occur and therefore denote the frequency.
Multiply the frequency of 2 volt drop events by 60 and you have RPM. In the scenario above the minimal volt drop may have influenced the RPM calculation.
Could you confirm, was this engine cranking faster than 183 rpm?
Below is an example of the typical volt drop detected from an engine with good compression
To access the voltage waveform on channel A of the Pico Diagnostics Relative Compression test click on the “Display Raw Data” button
Note you can also zoom on the “Raw Data” by clicking on the waveform and drawing a box around the area of interest (Marquee/Window zoom)
To zoom out or hide the raw data, right click on the graph view
I hope this helps, take care…..Steve
As jueja as mentioned, the confusion has crept in because all cylinders are, or appear to be, equally low (0 Bar)
Relative compression results are calculated by comparing the largest volt drop across the battery (best performing cylinder) against the volt drop acquired from the remaining cylinders
I.e., the remaining cylinders are compared “Relative” to the best performing cylinder
This cycle is repeated for every volt drop event based on the cylinder count value entered into the software
E.g., Entering “4-cylinders” provides the interval over which the 4 volt drop events (for 4-cylinders) are repeatedly analyzed during cranking
In your scenario below, we can see very little volt drop across all cylinders and therefore the comparison suggest that all remaining cylinders are near 100 % of the volt drop detected for the best performing cylinder
- Image 3
RPM is calculated based on the frequency of the signal and the entered cylinder count. The software will identify 2 volt drop events (one crankshaft revolution) calculate the time taken for these events to occur and therefore denote the frequency.
Multiply the frequency of 2 volt drop events by 60 and you have RPM. In the scenario above the minimal volt drop may have influenced the RPM calculation.
Could you confirm, was this engine cranking faster than 183 rpm?
Below is an example of the typical volt drop detected from an engine with good compression
- Image 4
- Image 5
- Image 6
I hope this helps, take care…..Steve