How to perform a compression test with a scope (Verus-Vantage)

[@ScannerDanner]

@MrKevg59 Depends what your market is. There is no better scan tool than a factory one, but if your an aftermarket guy like me and work on everything the Verus is the way to go. There are cheeper alternatives though, you could go with a Solus Pro and Vantage Pro which would cost you a few thousand less than a Verus. Snap-ons troubleshooter and component test meter is un-matched in the aftermarket for experienced based help.

[@ScannerDanner]

@bartewer This test is used to determine the cause of the misfire, not which cylinder is misfiring. Imagine you are working on a system where the intake manifold covers the back cylinders. The middle cylinder in the back is misfiring as noted by misfire counters and a trouble code. You would need to sell a customer an upper intake R&R to inspect the misfiring cylinder for a lack of spark, fuel or compression. With this method you could identify a mechanical problem without removing the intake.

[@ScannerDanner]

you can and the amp probe you buy does not need to be from snap-on. thanks for giving me a chance and buying my eBook! I'll try to help you in any way I can.

[@Thefox2000unit]

Just got the low amp clamp the other day. Looking forward to using it for easier/quicker diagnostics. Love all of these videos! Very helpful!!👍🏻

[@felplayvina]

I did this test with my old vantage and low amp probe set at 40 amp, really good test..Paul..thank you.

[@ScannerDanner]

@romeoadryan I don't see it damaging the probe as it just reads magnetic field strength. I think the only concern would be accuracy of the probe at higher than normal amperage. Which is not a concern for this test as I am looking at relative numbers.

[@integrityautocarehomeofthe145]

Brotha Dan, THANK-YOU for helping me make a big difference in Auto Repair and showing our customers that those shops that can keep up with diagnosing and fixing today's CRAZY COMPLEX cars are just like a good Doctor..always learning and studying, even on a Sunday! Dr Rob The Car Doctor over and out.... PS: Love your e-book as well.... :)

[@ScannerDanner]

Thank you brother

[@ScannerDanner]

@import0408 as long as the low amp probe fits the wire you shouldn't need a high amp probe especially because i generally only use it for starter current and as you saw in this video i used the low amp probe

[@ScannerDanner]

No, it should have worked on the 40 amp setting. Did you make sure you were on the correct battery cable? Sometimes systems will run multiple main cables, just make sure your on the one going to the starter itself.

[@65blablabla]

Great info and step by step on how to do this I just bought a modis and running a shop alone I need to learn these skills,thanks for great tech info videos.

[@Landonh-g5m]

never even occurred to me to do a fast compression test like this..right on great video

[@joemikos900]

Great job Paul! I'm going crazy at Car Care Ministry but in a good way. This past Saturday was our monthly Ministry's car repair day where our volunteers come in. We did about 13 cars! My job is primarily diagnostics. I had to call two bad computers, both injector drivers as well as a clogged exhaust and there's the regular MAF stuff ect. I have to be accurate because as a Ministry our funds are donated and obviously we have to be good stewards. Plus as you always say and I couldn't agree more..."don't be a parts changer". My problem is we don't have adequate diag equipment. My friend Eric "ETCG" did get OTC to donate an Encore scanner which has been our go to scanner and we are very grateful for it. As of now we don't have any subscription service e.g. All data. We are hoping to upgrade due to the fact we are taking on more cars in light of recent publicity. For "front door" (scope) type testing I'm limited to (no scope) a multimeter and Power Probe. Anyway I was wondering if the old Vantage would work for relative compression. That's something I think is in our reach. I've seen them on EBay for around $3-400. Just need to know if it does R C. Thanks again Paul

[@ScannerDanner]

It will but we need to get you a Vantage Pro. We are upgrading our equipment at Rosedale Technical College. I can check to see what our Snap-on rep will sell the trade-ins for if you want? It would be an older Vantage Pro but to be honest. The Vantage Ultra and Edge where downgrades in my opinion. I loved the VP. I absolutely hate the newest one. It is slow and lanky. Yeah, it is touch screen but so what, even that sucks.

[@joemikos900]

ScannerDanner That would be a dream! A for real game changer. I literally just got home from the "Barn" (our Ministry's shop) because I'm struggling with a 3800 GM donner car that I had to do an old school gauge compression test on and will have to take off a valve cover to check for timing chain slack chasing a weird idle misfire. The car is irrelevant but the point is I would of been home hours ago and not OCDing about the diag if I had a scope...LOL I will send you a quick email in case it works better for you. Thanks so much, I'm excited that there is even a chance. Amazed you even have time to respond. Either way, you are much appreciated. God bless, goodnight

[@ScannerDanner]

@romeoadryan Good question. It was the only probe I had with my Verus. I would have used a high amp probe if I had one.

[@ScannerDanner]

cool! I'm sure it isn't as clear on that screen but it is good to know it is at least do-able

[@ScannerDanner]

@DerekLMartin I do but it is not complete yet, as soon as it is done I will post the link for you. Thanks for your interest and comment!

[@OneManOnFire]

While I know this video is old I'm definitely considering a older verus as they're more affordable as the newest car I'm working on is a 2008

[@ScannerDanner]

that would be a good question. I have never done a relative compression test on an odd fire engine. I imagine that it would be as you said have natural dead spots

[@Nudnik1]

Sometimes irregularities in starter itself draw can send a erratic signal .Very often most good mechanics car "hear" variations in cranking sound indicative of a low or Dead cylinder. Good test and use of scope. Thanks

[@ScannerDanner]

@dreamer2355 no problem! thanks for the comment

[@PaulysAuto]

Thanks for this video Paul, very good tests to know!

[@ScannerDanner]

@JrUnKrownedKing Thanks for your comment! It really means a lot.

[@triggera3851]

I definitely heard it. Your knowledge and information is gold.

[@bartewer]

Why would you use this to isolate a misfire? I could see as a general quick check of engine health, but wouldn't it easier to pull the wires off one at a time or check the misfire counter on a scanner? I have a scope but this seem the long way around the barn to diagnose a misfire.

[@oscarventura8337]

Thank you Mr. Paul you really have a a flair to teach this important stuff.

[@ScannerDanner]

Thank you! I am a teacher at a technical college, so this is good to hear :-)

[@Iliketobrap]

Wow ive never heard of this method before. Very cool. Thank you sir

[@KALUPO78]

Yes, Not all scanners have a lab scope built in. A lab scope shows the wave form. A code reader tells you the code. A scanner will show what the engine/sensors are doing. IF it is a bidirectional scanner you can control sensors and motors ect. You can roll up windows, flash lights move the gages things like that.

[@KALUPO78]

If its a EFI And most are nowadays if they have coil packs Or COP Just use the injector disable to check RPM drop. If it has a distributor, you can reach the plug and/or distributor.

[@thebronze907]

romeo, sure, but just watch the battery voltage. As the amperage rises on due to the pressure on each cylinder, the battery voltage drops. It typically what I do, after all, it is just a relative compression, we are figuring out the pressure (unless you have a pressure transducer installed, which is super-cool).

[@labradormcgraw]

Still the best on KZbin.

[@ScannerDanner]

Thanks my friend

[@organicvids]

to figure which cylinder is bad remove plug number one and count spikes from there

[@12mak]

Wouldn't that effect the other cylinder's reading.. as in the same when doing a mechanical compression test..

[@pumarobo]

Just add channel 2 to the cyl 1 coil pack and use that as cyl 1 reference

[@ScannerDanner]

no sure, I never tried it. I think you probably could do it but synchronizing it with another channel may be difficult at best

[@AmericanLocomotive1]

I meant that since the Dodge V10 has irregular firing intervals, there would be "dead spots" naturally, and it would seem to me that it would be difficult to tell those natural dead spots from a cylinder with low compression.

[@ladillando1]

Today I was trying to do the relative compression in a vehicle with the Verus following your instructions but was impossible. This is not the first time I was trying. Probably this scanner is bad.

[@radmilakrejci8581]

i know you said you disabled the ignition (fuel pump fuse out i assume or similar), my question is when you have your helper crank the engine is he on the gas pedal when cranking? thanks

[@ScannerDanner]

@import0408 Yes, you can use the RPM pick-up and trigger from it, however once you freeze the capture you will lose your reference point. Go to AESwave dot com and buy a sync probe which will plug in to one of your channels. Watch my pico relative compression test to see what I am talking about. Email me and I'll send you a link to the sync probe.

[@billrimmer5596]

Great vid! Could u also use a second amp probe on channel two. And trigger off a coil or injector?

[@sollykhan2385]

AWESOME video, Dan, Thank you for this great info filled Presentation, much appreciated, will watch more, BLESS 🙂😇👍

[@romeoadryan]

@ScannerDanner can not blow the current probe when the current draw is over 80 amps ?

[@mohammedcherifi9206]

The best channel for ever

[@josueivanruiz]

@scannerdanner I was just wondering if an exhaust restriction would be a variable in relative compression testing especially on a V engine. if the catalyst was plugged on one bank, would that give u low humps on those cylinders?

[@ScannerDanner]

+josue ruiz I think that is possible

[@simonilett998]

I believe you would certainly see a difference on the bank with a plugged converter, so long as each bank has a separate exhaust header. Current should go high, and voltage should go low each time one of the cylinders on the 'plugged' bank came up to compression. (ScannerDanner) Would you agree Paul?

[@DraGSLight]

hi ! would you be able to hear it in any kind of scenario if you had low compression in one or more cylinders ?

[@mrgalea100]

Can I do this test by putting my snap on scope in series with the battery and the starter? Will this hurt my scanner?

[@sureshbabu-fl5kx]

Great experience to my work shop . thank you very much sir

[@ScannerDanner]

For sure, but the firing order was 123456

[@import0408]

You said you would never put a plug or a injector in it. What if you had a leaking injector that washed the cylinder? I feel like this could be a variable.

[@MrKevg59]

would you say that the verus is the best for vehicle diagnostics.

[@PANOS9916]

Something that I have not clarified yet is when should we use the low amp clamp and when to use the high amp clamp

[@ScannerDanner]

I learned the limits of the low amp probe in this video kzbin.info/www/bejne/aoq6dH6wpceamJI It is 2.5v or 250 amps (i think) The other consideration is wire size. The jaws of your low amp probe must close all the way.

[@ladillando1]

Hoy trate de hacer un prueba de compresion relativa en un Mitsubishi Montero Sport y me fue imposible. El Verus en funcion de scope se congelaba y tenia que hacerle restart. Despues de 4 intentos y mas de una hora de frustracion, decidi abortar las pruebas. Alguien podria decirme que es lo que esta mal? Este problema no solo esta relacionado al scope, tambien lo hace con el scanner.

[@romeoadryan]

why use a low current probe when in the circuit is over 400 amps ?

[@cam72100]

Hi Paul, my name is Melchor I just bought your Ebook is a very good information book, I have been learning a lot. I just got the modis from snap on and I was wonder if I can do the relative compression test with this tool? and if do I need the low amp probe from snap on or can be done with any other brand of low amp probe? thanks

[@elora2525]

What about if my amp clamp is 20-40, will it work? And the conversation will be the same? 1 amp=10mv?

[@Dansyoung]

Will this test be sensitive enough to identify a cylinder that has compression, but there is a valve that has a duration problem. I work on dodges and it’s common to have a hemi with a wiped camshaft lobe, so the engine will have good compression it just won’t pull as hard as the other cylinders. Or a pressure transducer monitoring the cylinder pressure will be the best option? Thanks

[@SS-U23]

Thank you so much for this video. However, I missed something about the amp clamp and the tool that you connected to your Verus- vantage scope. The most important thing that I missed is that the amp clamp you used is a low amp clamp that goes up to 60 dc A. However, you had everything set up in spite of the fact that the starter may have drawn up to 200 dc Amps. Man, I really do not get how the low amp clamp handled like 150-200 DC amps that the started drew. Thank you again for sharing such a great video with us.

[@ScannerDanner]

This amp clamp can measure up to 250 amps. It's voltage output is limited to 2.5 volts. Amp probes produce voltage in the presence of a magnetic field. The current flow in the wire dictates magnetic field strength. Add a little math conversion and there is your inductive low amp probe. Hope that makes sense.

[@mertylmaz2179]

@@ScannerDanner The amp probe is able to measure max 60 amp, how could this be possible, it may give false readings over 60amp, though waveform seems allright.

[@ScannerDanner]

@@mertylmaz2179 read my comment in this same thread, it explains it.

[@CoroPlanesLLC]

A friend took his Honda van to the dealership, and they tried to sell him an engine replacement using this test. They told him he had poor compression in multiple cylinders and the engine would have to be replaced. They wanted $6000. A few days before, it began making a clattering sound that he thought was coming from the top of the engine around the valve covers. Suddenly the engine began running very bad. It would not idle without giving it some throttle and could not be driven. He asked me to look at it as a second opinion. When I heard the engine, it sounded to me like an engine with a valve timing problem. I pulled the inspection plugs off the timing belt cover and I could see a huge amount of rubber debris and some belt chunks, but the belt was still in place. Turns out, one of the tensioners failed. The belt slacking and then getting tensioned again was the sound he was hearing. The belt could only take so much of that abuse before it jump a tooth or two on a pulley. The dealer was going to replace an engine for $6000 when all he needed was a $100 timing belt and tensioner set. He helped me change the belt and he was able to learn a lot about his engine in the process. If I learned anything from your videos, it's that you should never simply replace parts based on what the scanner tells you. It takes a little troubleshooting, in addition to the scanner to get a proper diagnosis!

[@import0408]

How would you hook a high amp probe up to the verus. Would you use the same 2volt conversion cause there is no option in it for a high amp. If so is there really any use for it with this scan tool other than it has a larger clamp

[@russellmcallister6830]

Hey paul. Can i use this method on heavy trucks with my verus using the principle volts dc and and doing a conversion. Select 10volts and convert to 1000 amps which i reckon it will draw?

[@muhindojehoiadapatience4455]

Thanks Paul. Am from Uganda, bought your ebook and its amazing. Am learning alot. Can any other cheap scope do the work,i may not be able to afford the vantage pro or verus ??

[@ScannerDanner]

Check out the uScope from my affiliate tool pages on my website www.scannerdanner.com

[@markjohnson8162]

I’ve tired this test with my modis ultra set it up using the same voltage and timescale and I don’t have the same readings . Could you please help me

[@ScannerDanner]

Mark, post this to my forum and share your screen with us. We can help you for sure! It is free to join www.scannerdanner.com/forum/post-your-repair-questions-here.html Hope tp see you there!

[@import0408]

Is there another way to do this with out the sa2000 tool. Our shop has a 4 Chanel scope--modis but we do no have the adapter for the primary ignition.

[@BespokeRyan]

Very awesome video I will put more use to my verus edge and low amp probe, recently also took my DMM home so I’d get the most out of my tool and use the built in DMM

[@brianmason1414]

AWESOME AWESOME AWESOME content.... unfortunately, right now I only have access to a Pico (shop equipment), but as soon as my SO account can take it, I plan on getting a Modis or something similar to have my own.

[@mustangdemon87]

Modis ultra with euro pack is half off right now fyi

[@Mike-yq7ce]

I love my modis it would be a good buy. James Lucy is correct I bought a modis last month for 3100 off the snap on truck

[@billwilliams6338]

SCANNERDANNER, when one or more pistons are NOT giving any compression. What would be the problems on the cars engine? you have to replace the piston or the actual engine block is cracked inside that piston cylinder and have to replace the whole engine block?

[@ScannerDanner]

valve, valve seat, headgasket, worn rings, broken connecting rod etc etc

[@billwilliams6338]

@@ScannerDanner thanks for the help ++ I disconnected the Temperature sending unit/temp sense, so How can I test the instrumentation temp gauge in my cars dash board by itself to check if its working correctly, what do I need to do?

[@billwilliams6338]

@@ScannerDanner thanks for the help The water pump is pumping how much water and coolant? how can I measure this how much the water pump is pumping? I don't know why they call it a water pump because its not pumping only water its pumping coolant. The Water pump only pumps coolant not water into the engine only when the engine is warm and HOT not when the engine is cold? yes I can pressurize the system to 13 to 15 psi to find external leaks using a radiator pressure tester. But I want to measure the Pressure of the system while the car is idling and running at higher RPM to measure the Pressure of the PSI of the system, How can I do this?

[@ScannerDanner]

@@billwilliams6338 the water pump pumps whatever you have in your cooling system and you cannot do the test you are trying to do, nor will it tell you anything. The only psi test you can do is with the engine cold and the system filled, start the car and then keep squeezing the upper rad hose, if it gets rock hard very quickly, this is a confirmed combustion leak into the cooling system. (headgasket/cracked or warped head)

[@meblake7359]

You didn't mention the polarity direction of the low amp probe. The arrow on the amp probe direction.

[@ScannerDanner]

"With the correct polarity" :35 seconds in

[@meblake7359]

@@ScannerDanner which direction is the arrow pointing?

[@ScannerDanner]

@@meblake7359 conventional theory current flow (pos to neg)

[@meblake7359]

@@ScannerDanner and if you connect the inductive clamp on the negative cable the arrow should point to positive?

[@ScannerDanner]

​@@meblake7359yes sir!

[@romeoadryan]

how about performig a compresion test measuring the voltage drop across the starter cable ? would work ?

[@yanierolivera4678]

Hi Paul, I dont find myself doing many relative compression test. I tried doing it the other day on a 98 honda crv. I was using a high amp probe set on a 60 amp scale. (10mv/1amp) Set the scope to volts dc, 2 volts on a 1 second time base. A got a wave form but it was always dropping below the 0 volt scale. I tried using my low amps probe, same settings and the same thing happened. Trying to think where i went wrong. All the best

[@ScannerDanner]

Flip your amp clamp over, they are polarity sensitive. Or select invert on your scope.

[@yanierolivera4678]

Paul I tried flipping the clamp over. When I used my snap on low amps probe the arrow on the clamp was pointing toward starter motor and same thing happened. I had peaks going over the positive side and they were even but at the same time I was getting almost like a mirror of the positive wave form below the 0 volt line. Later on i was going over my scope settings and found that I had checked "on" the AC coupling function from a precious alternator diode test I had done and I never unchecked after when setting up the vantage for the relative compression test. I have not tried to do the test again but i will for sure. Maybe this is what caused an erroneous wave form to display. we'll see. Thanks for your reply! All the best

[@felplayvina]

Hi Paul, can I do this test with the low amp probe at 40, with the old vantage mt2400 and the RPM pick up? or at least one at it time?

[@nickayivor8432]

Good Evening ScannerDanner 🙏 ✨ Have a great day and take care ScannerDanner 🌟🌟🌟🌟🌟🌟 Tutorial Great 👍 👌 👏 From Nick Ayivor from London England UK 🇬🇧

[@5am8011]

how do i get your e book my friend at home bought it he z nothing but good things about it iv read bits and pieces of it but would like me own. can yu do some can bus videos? your doing a grea job cant stop watching well earned pat on the back

[@contagiousFX]

Paul, your setting is at 2V/2s, my question is how much voltage should you see drop if a cylinder had like 50-100 psi lower than others?

[@ScannerDanner]

Not sure. I don't use this test that way. I just want to make sure they are all even. If they are not, there is a problem.

[@j.helvie6563]

***** This test is more of a relative comparison tests than a measurement. You'd see a lower hump in relation to the others, but a specific voltage amount wouldn't be useful. Under these condition, a somewhat lower hump would lead you to a conventional compression test to measure specifically & then a leak-down test to isolate leakage location.

[@phillipkang1782]

Hello Mr. Danner. Im loving your videos and knowledge your are sharing. I was wondering why this test doesn't work on the scope part of the verus and only on the volts dc part. I just figured since the scope's faster it would pick up the compression signal but it goes straight up to 12-14 volts and doesn't move until i stop cranking. Thanks again and I love your lessons! Take care.

[@ScannerDannerPremium]

Phillip Kang This was the scope. Volts DC is just a default for a single channel.

[@ScannerDanner]

not at all. every cylinder is still individual and fires in sequence

[@lambertotejada7769]

I bought a second hand Vantage Ultra 13.4 less than a half price of the new one, but I don't know where to hook up the scanner to the DLC

[@pfournier623]

Lamberto, the Vantage is a nice tool, but it is not a scanner. It is a slow but adequate for most automotive purposes power graphing meter/lab scope. You cannot use it to collect scan data. For that you need a true scanner. The tool Scanner Danner is using is a combination scan tool/lab scope which will do both.

[@lambertotejada7769]

Thanks Philip for the explanation. I thought it can be used for both...I'm not wandering anymore

[@romeoadryan]

@ScannerDanner i have the same tip of probe and and I'm afraid to connect my probe in this way because I know cureent draw up to 400 amps . What do you think ?

[@ivaneu1]

Great video Danner, where can I buy that tools in New York or New Jersey? I'm going go there in next month.

[@ScannerDanner]

What tools? Snap-on tools are sold by Snap-on from their tool trucks.

[@ivaneu1]

+ScannerDanner I'd like a versus scope. Thanks for your reply.

[@charlemagneverzosa4869]

Hello Mr danner.what should I do if I can't lig in to my account on your premium video or something?

[@charlemagneverzosa4869]

It said wrong password and email

[@charlemagneverzosa4869]

???

[@AmericanLocomotive1]

I'd imagine this would be hard to determine on odd-firing engines like the Dodge truck V10

[@WillsHellaHeat]

Just bought a verus 325 the wireless version what cabl do i need to buy to hook up my obd1 adapters?

[@ScannerDanner]

there is an adapter the connects to your wireless VCI 16 pin connector, I forget the number of it offhand

[@LewsSpeedShop]

Is there a difference between a labscope and a snapon scanner for tests like these?

[@texas77563]

is the snap on verus still worth buying a used one in 2020. or do they have cheaper ones that do the same thing nowadays?

[@ScannerDanner]

stay away from the Verus and Verus Pro as they use an obsolete operating system (windows xp). My Verus Edge is window 10 I believe

[@KALUPO78]

What about a dual plug setup or a multi spark?

[@sampierson402]

so when you are shorting out the coils with your test light, or unplugging a injector connector, your trying to find which cylinder is not contributing. 10-4. on an OBDII vehicle is it invalid to unplug the coil over plug connector?

[@sampierson402]

my thoughts have been jumbling since I bought your book. piecing all this good info together. so I'm also thinking this........... for a really fast direction test on an OBDII car, with a misfire, not sure which cylinder... could I unplug each coil over plug connecter (one at a time) and listen to rpm? then by doing the same thing with the injector connectors determine if there is a fault in the ignition or fuel delivery..?

[@forrestkim4828]

You can do vacuum test instead current clamp also ! ...good job. !!!

[@chriscanty8214]

I have a 02 chevy cavalier the humps don't look like the ones you have on the video I hooked up at the battery should I move my clamp closer to the starter wire does it matter which post I use positive or negative?

[@ScannerDanner]

either post is fine, but must be around the correct cable if you cannot get the jaws of your clamp around all of them.

[@chriscanty8214]

Played with the settings changed the battery in the clamp perfect waveform do you offer training on the vantage ultra

[@jaimesustaita285]

Hello paul y'all ever sell those scanners at a discount rate after y'all get new ones, sure would like to have one, unfortunately can't afford a new one, and most of the work i do is pro bono because i love help people out.

[@ScannerDanner]

We do not. I'm sorry. I know Snap-on does though as we trade ours in when we upgrade.

[@radmilakrejci8581]

Paul! subscriber to your channel here! and proud owner of the book! Everyone should get the book! quick question here! if i would be testing starter draw , is 600amp clamp safe to use with verus scope, i heard stories about modis getting fried up when using high amp probe on failing starter (they draw 400amp ). is there some kind of protection/amp conversion as the clamp itself is rated for 600A, and settings on verus scope are 40A. You should make a video btw on how to use scope and probe to do a starter draw,

[@Evesautomotive]

Have seen low compression caused by washed out cylinders too, which was caused by a bad spark plug (older cars). Seen this sting a few techs.

[@sollykhan2385]

or a vehicle that had be laid up for a while, and got internal rust on valves/ seats, bore etc, 🙂👍

[@kiracat99]

Mr. Danner-You don't need a high amp clamp for this test? It would not harm the 60 amp max clamp? Thanks

[@ScannerDannerPremium]

+mark schaefers no you do not and you will not hurt the amp clamp but you are limited in that it will not read more than 250 amps or it will not produce more than 2.5 volts on the 10mv/a scale

[@xxrevansblackopsxx]

hey paul I have a quick question, I wanna perform a compression test on my chevy trailblazer i6. I know im supposed to take out the fuel pump relay but am I supposed to disable the ignition system too?

[@oscartrujillo5223]

ScannerDanner Another awesome video. I am a bit skeptical on the effectiveness of this test in that, from the video a relative compression test would clearly show a completely dead cylinder without problem, which in most cases, with some exceptions, are easier to identify without much testing. I would agree that this tests most powerful use would be in checking compression at inaccessible cylinders. In your experience how have you found the effectiveness of relative compression testing with more common engine mechanical faults such as burnt valves, head gasket issues, etc.? Thanks dude!

[@contagiousFX]

Paul, in which cases where I cannot use the low amp probe to check relative compression testing? Which cars? Also what would happen if it goes over 400 amps? Will I damage the scope or the probe?

[@ScannerDanner]

You will not damage the probe and you should be good with all cars. I've yet to see one with that kind of amperage cranking. Initial crank yes, after that, no

[@contagiousFX]

ScannerDanner thank you kind sir.

[@evansjean]

What if your compression is low but missing completely? Let's say you got 120 and all cylinder and one of them is at 70 psi would that show you missing compression also?

[@ScannerDanner]

Yes, it will show as well. Watch this video kzbin.info?o=U&video_id=tZWsOupUzhY Start at the 5 minute mark. It is a Hummer with a leaking valve causing low compression in one cylinder. Thank you!

[@alekstolstoi]

can I synch from the fuel injector number 1?????

[@destruxxx]

It would be easier to sync to the spark on #1 because it fires closer to TDC on compression.

[@cucogallegos3974]

thanks you are awesome! needed to know that thanks again!

[@Viper81766]

Great video. Will a 400 amp clamp be enough for this or do I need 600 to 800 or such ? Thanks brother

[@ScannerDannerPremium]

If you are buying a high amp probe get the 600. Most of the time I just use my low amp probe but it will not read higher than 400a

[@alejandroamaro8303]

Hi Paul. if im using an oscilliscope for testing high amperage with an amp clamp do i need to run it through an attenuator ? or is the attenuator just for high voltage readings? such as an injector voltage waveform. would i ever need an attenuator for measuring current on cars ?

[@ScannerDanner]

+Alejandro Amaro amp clamps produce millivolt signals that are equivalent to the current being measured. You will never need an attenuator for these

[@alejandroamaro8303]

Ohh. I see. Okay thank you my friend. I have my scope on its way through mail and i dont want to burn it in the process of learning how to use it. Lol

[@Jordan-ym5gf]

Couldn't you also just hook up another amp probe to one of the plug wires?

[@ScannerDanner]

not an amp probe but a capacitive pick up when trying to acquire a signal from a plug wire

[@MrLuwitin]

hey mr. Danner. one question. I'm not getting a reading. could it be because the battery cable is too thick, and I can barely put my snap on clamp around it? if so what could I do?.

[@ScannerDanner]

+Ludguin More less yes, if the jaws of the amp clamp can not close all the way around the wire you will not get a good reading. so your other option would be to find the cable that goes directly to the starter and use that one. Or possibly use the negative cable of the battery

[@MrLuwitin]

Ok. I'll try that. Thank you.

[@danielgarcia9095]

+ScannerDanner did you have to setup year make and model?

[@ScannerDanner]

+Daniel Garcia no you do not, but you will need the firing order to sync the pattern

[@danielgarcia9095]

Big thanks

[@rodx5571]

Funny story, A buddy of mine had just done heads and timing chains on a dodge 4.7, no codes, but cranked unevenly and ran bad. i did a relative compression test, it was an interesting pattern, high peak, lower peak, high peak, lower peak, every other cylinder was weak. I immediately suspected one of the chains was off. Because there was no code i suspected bank 1, as bank 2 has the cam sensor in it. I put a transducer in cylinder 1 just to complete the diagnosis, I used it as the sync channel, it was indeed weak all along bank 1, by about 25 PSI., just for fun i put the transducer in cylinder 2 (give him his moneys worth), Ran the test again. I verified my suspicions. Because it ran, and it was only 25psi low, i told him its probably only 1 tooth off, but its definitely off. He pulled the covers and checked his timing, yep, as i diagnosed it, tooth off on bank 1. So i went through the whole procedure for timing these engines, He got it 1 tooth off, he never rolled the engine around by hand (with a tool) after timing it to feel for low compression and to double check timing. This you should do every time. Sadly, 6 months later he did something similar with a Honda, Gets in a hurry and forgets the final checks.

[@ScannerDanner]

nice find!

[@carlosmel2882]

Does this test apply to all vehiclea

[@ScannerDanner]

Yes sir

[@Carlosmelchor-y1l]

Is this test done with dc coupling or ac ?

[@ScannerDanner]

DC you can use AC coupling but that isn't necessary unless you decide to use battery voltage instead of current