How to perform a compression test with a scope (Picoscope)

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In this video I will be showing you how to use starter current to determine cylinder compression. First I will show you a known good pattern, then I will simulate a no compression problem in one cylinder by removing a spark plug. Finally, I will show you how to synchronize the starter current waveform with an ignition firing event in order to determine which cylinder in the firing order has the compression problem.
Tests shown
- cranking compression test with a scope and high amp probe
- how to synchronize a compression waveform to ID the no compression cylinder
- how to perform a clear flood crank
- how to use a single trigger setting on a scope
- how to set a filter on a scope waveform
Tools used
- Picoscope Automotive 4 Channel Scope
Playlist
- (Chapter 1) Misfire ID, Compression Tests, Vacuum Leaks, Fuel Trim, Head Gasket, Restricted Exhaust, Low Power, DMM
• (Chapter 1) Misfire ID...
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For more information on th is topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium right here on RU-vid. There is a 14 day free trial.
On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium www.scannerdanner.com/join-sc... There is a 14 day free trial.
On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC.

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Опубликовано:

1 фев 2012

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Комментарии : 75

@andyhodgev.a.g1291 Год назад

Cheers Dan CC-650 Amp clamp just arrived so we are game on for trying this test tomorrow 😊

@keunsupark9180 5 лет назад

Thank you PAUL ~ Relative compression/ignition timing

@willyck948 4 года назад

if there was one trick thats helped me the most thats the WOT clear flood trick awesome🤘

@frank289frank 8 лет назад

Paul,first of all I just to thank you for the free trial of your premium channel. I just bought your ebook and it's great. more fun to follow your case studies. Secondly I just purchased a hantek oscilloscope and am in the process of figuring it out. lol but your book and videos are a great way to get started. thank you again for all you do.

@ScannerDanner 8 лет назад

+Frank Senick no problem! And thank you so much

@nickayivor8432 2 года назад

KNOWLEDGEABLE Sir ScannerDanner Good Morning Sir ScannerDanner Tutorial amazing 👏 thank you very much Take care and have a great day Sir ScannerDanner From Nick Ayivor from London England UK 🇬🇧

@urgentcareguy3 12 лет назад

Nice job! Very thorough. I have the same Pico. "People of the Pico " know why we are superior ! ; )

@vin605 7 лет назад

you are the best ! keep up the good work.

@ScannerDanner 7 лет назад

thank you!

@ScannerDanner 12 лет назад

Go to picoauto and post your concern on their forum. Let them know I sent you and they will be more than happy to respond to your concern and hopefully have a solution for you. Thanks for the comment

@ScannerDanner 12 лет назад

@foxholewilly On coil over plug gas engines I will use the PCM to coil, base circuit control signal, which is a 4-5v on/off square wave (3 or 4 wire coils) or the coil negative voltage itself (2-wire coils) to sync the waveform. If I cannot access the coils, I will connect to the PCM connector to do it. So on our gas engines there is always a way without pulling a plug.

@ScannerDanner 12 лет назад

@RUSS16V2 Yes, keep watching they are coming

@wyattoneable 8 лет назад

That Pico is sweet! Plus more affordable for a DIY guy like me.

@shawnlockard2370 10 лет назад

Thank you for all you that you do here.Takes me back.

@ChicoDeon 2 года назад

YOU ARE THE MAN

@ScannerDanner 12 лет назад

@ScannerDanner BTW Pico does have a diesel version where the high amp probe is a 2000 amp instead of 600 amp

@myrepairshopinc.8213 4 года назад

Thank you!

@stephanevaucelles6378 3 года назад

thank for video

@ScannerDanner 12 лет назад

@DiyMech Sorry I didn't respond back sooner, I've been very busy with all of this. Diesels aren't my thing so I have no further help to offer.

@ScannerDanner 12 лет назад

@ScannerDanner Also it would need to be a sequential injection design for this to work

@IamReadyToRock 6 месяцев назад

nice... from Peru

@ScannerDanner 12 лет назад

@wilkk I am not a diesel guy, but I would imagine you could sync it to an injector. Diesel injectors spray on the compression stroke right?

@tajindersingh7932 5 лет назад

Wow thinking beyond

@wilkk7867 12 лет назад

@ScannerDanner - it depends on engine. For example, in my car i have "common rail" system with piezo-electric injectors which sprays three times per cycle: First, called "initial spray" occurs during induction/compression stroke, second -"main"- adds more fuel during power stroke, and third during exhaust stroke (mainly to reduce NOx emissions).

@GRUSSNewton 12 лет назад

Very helpful video! Will you be doing more pico related videos? Gr

@TRcustomengineering 12 лет назад

@wilkk You can still hook an amp probe to the starter but you won't know what cylinder is which on the graph... But there still could be a way to do it on diesels that I don't know about. :/

@padraiggalvin2807 5 лет назад

Awesome video again. very handy test. Stupid question here but can the scope or amp clamp be damaged when the amps go over the scale.does anyone know this?

@DiyMech 12 лет назад

Hello SD, soooperb videos, my question is:- when doing relative compression on a diesel what would be the best "sync pulse" to use in order to determine piston nums as you obviously dont have spark plug leads you can use to sync ? crank position sensor ?, tap into injector pulse signals? Keep up the guid work

@ScannerDanner 12 лет назад

@foxholewilly I don't see why not.

@jnarez1 9 лет назад

Will the 2200 series picoscope do the trick for troubleshooting a lot of this stuff.

@phillipkang1782 9 лет назад

With a verus, how would you sync it with a distributor / wire ignition system?

@hamham4547 Год назад

Hello, Nice video Paul I was wondering what kind of rpm pickup probe are you using, is it from a multimiter kit? And you just add bnc adapter

@jasonthomas9847 11 лет назад

using the verus pro , do you have to have the SIA 2000 in order to do secondary ignition tests on a direct or waste spark system.

@MrJgonzalez2 11 лет назад

Paul, the second channel probe you're using set to voltage, is that the same probe you would use to read secondary kv voltage with the same set up?

@ScannerDanner 12 лет назад

@500hpsi I must be careful in my response. I'll just say for now that both of these scopes have there advantages and are great tools in the right hands :).....sorry

@mohammedcherifi9206 3 года назад

Hi mister paul i really appreciate your efforts in explaining different case studies i just want to ask you do you have to remove spark plug wires when doing a compression test because as i think the engine will start if you leave spark plug wires plugged in. Greetings from Morocco 🙏🙏

@ScannerDanner 3 года назад

@@mohammedcherifi9206 no, you can disable to ignition or fuel injectors by removing a fuse or disconnecting power to the coil or coils

@mohammedcherifi9206 3 года назад

@@ScannerDanner thank you sir

@MrJgonzalez2 11 лет назад

Paul, do you have a part number for your rpm pickup probe?

@DiyMech 12 лет назад

Ok, I've just read the rest of the responses, my guess is therefore the injector pulse(s) signal.

@wilkk7867 12 лет назад

Is it possible to perform similar test on a diesel engines? They have no ignition coils, so how to know which cylinder is which? Maybe connecting to the crankshaft position sensor?

@lifeInProgress_8020 12 лет назад

How do you like the pico vs. the modis or verus? it easy to set up compare to the snappy?

@MrJgonzalez2 12 лет назад

Is it possible to do this kind of testing using injector pulse as a sync?

@BoltThrower321 11 лет назад

When testing compression via starter current at common rail or UIS engines...I suppose there is no way to trigger the 1st cilinder, because I've to disconnect the injectors or I need to record the camshaft and 1st cilinder injector signal to know which block of the camsensor stands for the 1st cilinder (what a text...) ?!?

@jamesbarratt593 7 лет назад

What is clear flood mode. And what do you mean when you wrote clear flood mode is done by eco when it sees TPS voltage at WOT?(What is WOT?)

@jamesbarratt593 7 лет назад

Found out what WOT is. Wide Open Throttle and clear flood mode is the PCM turning off the injectors and spark. Cheers for the video dude, im heading after a picoscope myself. Oh and a snapon scan tool because of the troubleshooter section. I have a maxidas 708 and its only a month or two old. It has no trouble shooter, and because of that, and after your video showing how cool troubleshooter is, im going for it.

@RC-Heli835 8 лет назад

Hey Scanner! You rock man! Quick question.........can I use a cheap Hantek Probe for the spark plug wire pickup to do this test with when I get my Pico Scope? The first thing I want to test when I get the Pico scope is one of our 5.4 F250's. It has a misfire under load with no code. I'm looking to get the 4 channel starter kit with the two amp clamps added in.

@ScannerDanner 8 лет назад

+ILTSYC thats a great kit and I'm not sure if the probe you are talking about will work with the pico. Where are you buying it from?

@RC-Heli835 8 лет назад

ScannerDanner I was looking at autonerd's 4 channel starter kit and add the two amp clamps on. Im sort of torn between getting that or a used Snapon Modis so Id have a good scan toll and a 4 channel scope in one unit. If I get the Pico I'll just get a good scan tool a little bit later. I was thinking maybe a Solus Ultra, Autel DS 708 or Autoenginuity Pro. I like the idea of PC based diagnositics because I can fix a PC but a handheld unit has to be sent in if it should need repair.

@albertsautodiagnosticsllc2130 4 года назад

What pico scope do you recommend ??

@JaySimons1 4 года назад

Paul, 6:32 sorry to be a stickler for detail, but did you mis read the firing order as 123456, when to me it looks like *621354* ..6 Or am I wrong,? its rare that I look at a dizzy car and need to know the firing order.

@skonyc3164 6 лет назад

Could this test be done with a two channel pico scope ? Great video

@ScannerDanner 6 лет назад

yes it could

@DavidGarcia-pn7ik 11 лет назад

Hey hows it going, im in an auto program in the bay area and i've found your videos to be very helpful. I got a question though arent you supposed to be able to see an exhaust wave in between all the compression waves?

@padraiggalvin2807 5 лет назад

No. Because the exhaust valve is open when piston is moving up therefore no compression or pressure on the starter motor

@jnarez1 8 лет назад

Could you use a relative compression to see if you have a clogged exhaust?

@scientist100 6 лет назад

You would need a cheap compression gage and plug it (by just pressing) in a O2 oxygen upstream (before exhaust). You should have no compression, if you do, then the exhaust could be clogged. But don't be fooled, do the same test in sections to find the true clogged component.

@ScannerDanner 12 лет назад

no because the injection timing is not synced to TDC compression

@DiyMech 12 лет назад

@ScannerDanner That's ok, fully understand, i'll have a play with a scope sometime.

@ScannerDanner 11 лет назад

no, but I got it at AESwave d o t c o m

@REPOOCNITSUJ 7 лет назад

Why did you use the # 6 plug wire? Just the closest one? I guess you could use any plug wire to give you a signal and then look at the firing order to know where the others fall? Just wanted to make sure I'm correct in how you're setting this up. Another awesome video!!

@ScannerDanner 7 лет назад

exactly, just the easiest one to get to

@ScannerDanner 12 лет назад

@urgentcareguy3 :)

@egyMag1990 7 лет назад

what do you mean by clear flood cranck?

@ScannerDanner 7 лет назад

Holding the gas pedal to the floor during cranking will cause the computer to cut injection pulse, making the car not start. Not all car have this feature.

@freddieco3487 4 года назад

How do we hold the throttle open if no "clear flood" mode is available on electronic throttle?

@ScannerDanner 4 года назад

For a compression test? Disable the fuel system (fuel pump or injector fuse or connector or relay)

@freddieco3487 4 года назад

@@ScannerDanner I meant HOW DO I GET THE THROTTLE TO OPEN if it's electronic. I use the live data from my scan tool and it shows the throttle closing after I begin cranking (fuel disabled). The PCM does not keep the throttle open.

@ScannerDanner 4 года назад

with key on, engine off, put the car in gear and step on the gas pedal (app sensor), the system may react and open the throttle plate