Pulse Sensor Diagnostics | Automotive Oscilloscope | Mechanic Mindset

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Introduction to pressure pulse sensor diagnostics. In this video we look at the different tests that can be performed with a pulse sensor and the basics of reading the oscilloscope waveforms. We also look at the Pressure Waveform Overlay to identify what to look for when diagnosing faults. Here I am using the PicoScope 2204A; great for anyone thinking of getting in to oscilloscope diagnostics!
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0:00 Intro to pulse sensor diagnostics
0:37 Pressure Pulse Sensor vs In Cylinder Pressure Transducer diagnostics
1:34 Different types of tests
2:12 Intake pulse sensor measurement
3:10 Exhaust pulse sensor test
3:30 Crankcase pulse sensor measurement
4:06 Coolant expansion tank pulse test
4:56 Pressure pulse sensor waveform analysis overlay
5:39 Diagnosing intake and exhaust valve issues
10:00 Diagnosing piston rings and bore wear with the pulse sensor
10:55 Diagnosing head gasket problems with the pulse sensor
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The Mechanic Mindset channel is here to help you improve your automotive diagnostic skills. We upload regular, easy to understand, automotive training and tutorial videos covering topics such as; oscilloscope diagnostics, PicoScope, CAN bus, waveform analysis and much more! Subscribe to stay up to date!

[@macdonaldsmotorworks]

great video Darren! I have a pulse sensor I've built and use it in the expansion tank as well. On a recent car that I was asked to repair the owner indicated he had a coolant leak I used the pulse sensor, my picoscope pressure transducer and sync'd on an injector to identify where the leak was. The owner couldn't argue with the diagnosis (I provided him a printout) and it was just so great to be able to diag this car with only a spark plug removed and my pico connected. It needed new head gaskets of course. Truly a fantastic diag tool and one I can't do without. I look forward to more of your videos!

[@MechanicMindset]

That’s awesome! Top example of putting this in to practice. More to come soon. Thanks 👍

[@Jpilgrim30]

The small ones in the cooling system are likely from the crankshaft speed increasing on the combustion stroke and you’re seeing that through the water pump spinning faster during those periods. I’m still amazed from time to time at some of the small details you can pick up in some of these captures.

[@MechanicMindset]

Agreed, it makes sense. Yeah for sure, so sensitive! Amazing little tools 👍

[@MrGooglevideoviewer]

Thanks for the tip. Never would've thought of that. Appreciated. Cheers!

[@joshbridges8410]

Lots of good theories about that ripple in the expansion tank. I would add that it might be due to expansion noise being transmitted into the water jacket through the cylinder walls. Remember a knock sensor is measuring the acoustic pressure wave traveling through the block. What you have there might be a secondary knock sensing effect.

[@MechanicMindset]

Thanks, we found the source! Check the latest video on this 😃

[@JNaimoli]

I also love using the pulse sensor to look for noises as if it was a stethoscope

[@MechanicMindset]

Ah yes, I’ve seen a few people use that method. Nice!

[@gerigesquiere66]

Many thanks for the video. I have making myself the pulse sensor like you have show on another video. Works perfect !

[@MechanicMindset]

Great to know! I might compare the DIY with these 👍

[@michaeldahlberg909]

Hello Darren. I really appreciate your videos. As a person who does not have English as my first language (I am Danish), I appreciate your very clear and easy to understand English. it's easy to understand your videos, and follow instruction even for forigners. Sláinte Mick

[@MechanicMindset]

Hi Mick, thanks for the feedback! Glad you are enjoying the channel

[@jakewrxdrift]

Once again thanks for the awesome video. I need to get me one of those pulse sensors now.

[@MechanicMindset]

Definitely! People have been using them for years but I only came across them in the last couple years 👍

[@utubefeltf55]

Many thanks for the video!

[@robertmobileman8304]

nice one ,good to see you back and sharing your knowledge cheers

[@MechanicMindset]

Great to be back on it. Moved house and weather hasn’t been great, but getting garage sorted and summers coming! 😎

[@renatairmarius123]

Thanks for video.

[@MiracleMAX]

Thanks for sharing - great explanation Darren! You are right, it is easy to struggle with the waveform interpretation.

[@MechanicMindset]

Cheers, it can be difficult. I will also have to follow up on this as the intake and exhaust waveforms are a lot simpler on NA engines (this one's TDI) - the turbo definitely confuses things.

[@MrFryfish]

Why would that be more complicated on diesel engines? They're spool are not spinning until about 1.500 rpm.. not many internal things are moving when the engine just runs at 800rpm..

[@JeffinTD]

Thank you for these most excellent videos.

[@MechanicMindset]

Thanks!!

[@bleebleblahble8833]

I don't see a lot of pulse sensor diagnostic videos. Thank you!

[@MechanicMindset]

You’re welcome, I hope it helps! Do you have a pulse sensor?

[@ttstang43]

darn good video, ive gotten into this style of testing and love it and this video definitely helps clear things up and greatly aids in education on it.. great job man!!

[@MechanicMindset]

Glad you enjoyed the video, they are great little tools, so cheap and effective!

[@ttstang43]

@@MechanicMindset absolutely...

[@MrFryfish]

What a valuable lesson! Thank you

[@MechanicMindset]

Get out there and give it a try! 😁

[@rolandorosales5530]

Great video!!! From what I understand the pulses on the expansion tank could also be from the cylinder expanding a bit on the compression stroke moving the coolant creating the ripples I think the become more pronounced during a Cranking waveform where there is alot more pressure.

[@MechanicMindset]

Ah interesting, I was thinking something similar. Amazing tool right? Cheers! 👍

[@SabretoothBarnacle]

Nice educational video. Just a note that you don't need to select Copy after Snipping. The act of snipping puts it immediately in the clipboard👍🏻💾

[@MechanicMindset]

Nice tip, I use it all the time and never knew that! Thanks 👍

[@Jo-hannson]

@@MechanicMindset try this one: shift+windows button+s you can then select a part of the screen where windows takes a screenshot and puts it directly to the clipboard :)

[@MechanicMindset]

@@Jo-hannson Nice tip!!

[@Lambros_Stefaneas]

Fantastic video.

[@MechanicMindset]

Glad you enjoyed!

[@amarabdelli487]

Thanks for sharing

[@stephanevaucelles6378]

hello and thank you for the video I still have trouble understanding waveform but by watching the tutorials several times I will finish it got there

[@MechanicMindset]

Get yourself a sensor and have a play with it 👍 Cheers Stephane

[@stephanevaucelles6378]

@@MechanicMindset I made myself one that works really well

[@MechanicMindset]

@@stephanevaucelles6378 Ah cool, I think I remember you telling me. Do you work a lot on turbo charges engines with the trucks?

[@stephanevaucelles6378]

@@MechanicMindset yes

[@MechanicMindset]

@@stephanevaucelles6378 I think the intake and exhaust pulses are not so straight forward in these engines. It also depends on the air intake

[@ismarmeskovic]

Brilliant presentation as always,I would strongly recommend rotkee pulse sensor,price is excellent and quality is amazing.

[@MechanicMindset]

Thanks! Great recommendation, I have been looking at their kit! Have you had anything else off them? They do a scope too 👍

[@ismarmeskovic]

@@MechanicMindset yes they have and listed price is 220 us for 8 channels not sure abut specs didn't check.I was about to try their in cyl pressure transducer for 105 us but it is out of stock at this moment.take a peak at their web store they have a lot of interesting gadgets.cheers!

[@markg6jvy135]

Nice job 👍👏👏

[@beanroy]

You should be teaching mechanics full time.... Awesome. Video

[@MechanicMindset]

Funny you mention that, I’ve been in technical training g for the last 11yrs 😂Glad you enjoyed the video! Thanks 👍

[@dan_austin__873]

Probably worth taking a measurement with the sensor blocked off to use as a reference. Because that's also a vibration sensor.

[@MechanicMindset]

Good point, I did hold it / isolate on some of the ‘shaker’ measurements, it didn’t make much difference in this sensor. Must be well built. More than I can say for my DIY job 😂

[@alrifainidal]

well done friend

[@MechanicMindset]

Cheers Nidal!

[@gcmd5852]

Great video. Might not be very practical on all vehicles but you might try the cooling system test with the belt off. The crankcase test is definitely cool. It's quick and easy too.

[@MechanicMindset]

Cheers George, good shout. Do you agree with the engine speed causing the peaks?

[@gcmd5852]

@@MechanicMindset I would agree, could be cooling system air pockets that’s why I mentioned removing the belt. Also on the crankcase test I try to isolate the system by blocking off the pcv.

[@train4905]

Awsome😊😊

[@lawsonthursfield6950]

Great video as always, another awesome use of delta sensor is fit the end with stethoscope so you can physically “see “ the noise on a component.

[@MechanicMindset]

Cheers Lawson, yeah I saw that method. What noises do you like use it for?

[@lawsonthursfield6950]

@@MechanicMindset only ever use this once on aux belt idler pulley , but to be honest my infrared camera had already pin pointed failure on idler pulley bearing.

[@MechanicMindset]

@@lawsonthursfield6950 Ah, I have one of them on my shopping list. What you got? I’ve been looking at the Flir and Seek for iPhone

[@joshuamyers3185]

@@MechanicMindset just reading thru comments and seen yours sir...buddy of mine got the Seek for his and it is pretty good....I have a Fluke VT04A and the Seek hooked to phone does better bc of phone camera interface....thanks for all the vids and knowledge Cheers

[@MechanicMindset]

@@joshuamyers3185 Ah cool, what model Seek does he have? Glad you’re enjoying the content!

[@klazzera]

These pulse sensors are just pretty much sensitive microphones. That leafy piezo element you've shown in the video is a sensitive sound pickup element. Even if you had the best head gasket ever possible, the walls of the engine block is gonna flex because of combustion events and a pressure wave(aka sound) is gonna travel through the coolant system. Hell you'd even see such small spikes even if you'd only just place that pulse sensor near the car while it is running, since you can hear the engine running by ear. Bonus: pressure sensors and microphones measure the same thing. However, pressure sensors are properly calibrated for a certain range and microphones mostly respond to speed of pressure change, not the actual pressure itself.

[@klazzera]

Great video though! Even though I knew such details about the sensors themselves, I'd never imagine such an application, it's genius! You've opened a whole new view for me with both your videos of in cylinder pressure sensor and this pulse sensor.

[@MechanicMindset]

For sure, these are so sensitive. It’s amazing how much sensitivity we get for so cheap. Pulse sensor diagnostics is really a game of comparison; and as you have raised, you need to understand what they are doing to be able to interpret any meaningful data from them. Cheers! 👍

[@ADDAUTOMOBILESERVICES]

👍

[@jwoeltje6949]

I have used delta sensors many times. I do my best to try to isolate the sensor from vibration because just bouncing around will generate a waveform. Looking at the test you did with the intake were you inserted the Delta sensor I would have to think the turbo is affecting that waveform. I’m gonna test that Theory Monday when I get to work. I Also suggest doing your pressure pulse in your intake and your exhaust while cranking instead of running. When I take a intake pressure pulse test I usually try to attach it right to the throttlebody and block off the intake

[@MechanicMindset]

For sure, I need to get a hook or something for it. I agree on the turbo theory and was going to try the same (go in at MAP sensor). I would say the same applies to the exhaust waveform too. I never tried revving it to see what happened. Any reason you prefer cranking opposed to running the engine? Cheers 👍

[@jwoeltje6949]

@@MechanicMindset I think cranking to me defines each cylinder better than actually running. Now the Crank case and the cooling system obviously you would need the vehicle running. Now depending on how bad the crankcase blow by was you wouldn’t need for the vehicle to be running. Something I see that some technicians that make pressure pulse sensors if you just have them hooked up you will see a voltage isolation depending on your millivolt range does that make sense?

[@MechanicMindset]

@@jwoeltje6949 So do you mean get a base reading before taking a measurement?

[@adrianlowes1848]

Great video as usual. The pulses you see in the expansion tank are water pump rotational pulses. As each blade of the impeller pushes more coolant you will get a slight pulse

[@MechanicMindset]

Someone added another dimension to this theory; the pulses are inline with the 4 stroke cycle because of the crank & water pump speed increases on each power stroke. What do you think? 👍

[@adrianlowes1848]

@@MechanicMindset probably find its a four blade impeller, cant see the 4 stroke cycle having any effect on water pulses in a good system

[@MechanicMindset]

@@adrianlowes1848 6 blades by the look of it and not sure on the ratio between the crank and water pump pulley

[@Lambros_Stefaneas]

@@MechanicMindset very very interesting this theory!!!!wow.i wouldn't think of this. But I think, it's a way to find out. Just make a video with the engine running, and then with the engine just cranking (disable ignition and injection/ or diesel injection,depending of the type of fuel ), and I think will we find out the results.

[@MechanicMindset]

@@Lambros_Stefaneas Good plan, I’ll add it to the list 👍

[@duraiddlimi9032]

thanx for the video, how to order these puls sensors?

[@juancarlosgonzaleztejera2151]

buenas tardes como puedo conseguir los sensores de pulsos

[@jorgeautomotrizfcsa.6436]

🤝

[@billytremoloband7456]

Very interesting video, and in typical Bmw n47 fashion the breather pipe is snapped.....!😜

[@MechanicMindset]

Confession: I snapped it when I removed the intake 😂😂😂. It was a little brittle 👍

[@billytremoloband7456]

Mechanic Mindset To be fair with those pipes even just the thought of removing the intake will snap them .....! Was thinking this pressure pulse diagnostic method would be a lot handier for diagnosing suspect ingeniums than using the compression tester as the glow plugs are a bit of a PITA

[@MechanicMindset]

@@billytremoloband7456 Awesome idea, give it a go! 👍

[@gypsysharky]

Hi what are the instructions for lining up the chart?

[@MechanicMindset]

Basically spread the chart between your trigger (ie coil). That will space the columns evenly depending on how many cylinders you selected

[@yemiasaolu1622]

Taking your reading cranking vs running, which one gives better result

[@MechanicMindset]

I suppose it depends on what you are testing. For pistons rings or head gasket I would think engine running would be best (capture high pressure from power stroke). For valve train issues, I don’t suppose it matters. Worth looking in to further 👍

[@kevencausby5964]

If you got a CO2 sniffer you might be able to detect the exhaust gasses themselves using the scope. I mean, sure the old-school blue to yellow shows SOME contamination, a digital sensor is much more sensitive to detection. Got a great video on a DIY version I could recommend if you wanted to replicate it as opposed to purchasing a pre-built one since you seem to like to show off affordable methods. And the same tool can be used on the tailpipe to detect leaking/faulty injectors.

[@MechanicMindset]

Yeah we used to do the same with the 4 Gas analyser in the dealer 👍. Block tester was always a bit hit/miss. Well that sounds interesting! Not come across something like that before, share the link 👍

[@kevencausby5964]

@@MechanicMindset kzbin.info/www/bejne/eaHJl3eGZruEnZY He's got a few videos including one to make one on that gas analyzer. There's a 3D print file if you've got the options. But I don't personally and am in the process of designing a basic prototype model for myself until I find a better box or decide to pay a printer.

[@kevencausby5964]

@@MechanicMindset Also be sure to check out his whole channel. Full of DIY tools on a budget for those who have the ability. The telegram group is very friendly and about learning/improving always. Super nice guy too talking to him.

[@MechanicMindset]

@@kevencausby5964 I know this channel, chatted with Dennis a few times! He makes some awesome gear! You on the HScope telegram?

[@jmc6940]

Would it be possible to measure cooling system pulses to identify power stroke events of each cylinder? Let's say you had a plugged fuel injector on a cylinder so good compression but no fuel or vary little.

[@MechanicMindset]

I like your thinking but I think there are better ways to test this - crank sensor signal frequency 👍

[@johnbonifas6040]

I just got one and I would like to no what voltage you set it and

[@MechanicMindset]

Low, under 1V maybe. You might have to adjust depending what system you’re testing; tiny weak pulses, go lower, strong pulses, go higher

[@martinguitarhd28]

Hi Darren. Can we use the pulse sensor on a diesel car and if so how do we get a sync to know which cylinder we are on .. Also can we use the piston chart on a different scope that is not laptop based.

[@MechanicMindset]

Hi, sync could be tricky on a diesel. I generally say you will have other information (misfire code, smooth running values) to help identify which cylinder a problem will be on. Otherwise, I suppose it’s sync to camshaft signal, or disconnect injectors and use noid lights so you can probe them. Defeats the object of this time saving test in my opinion. Re non laptop based, take a picture of the screen maybe? 👍

[@martinguitarhd28]

@@MechanicMindset Thanks Darren so if we did not use a sync we could still use the pulse sensor say in dipstick tube or exhaust or intake just to see if the pulses are ok.

[@gypsysharky]

Hi, sorry but what about the vertical setting of the table ? How do we align it? Thanks for the video

[@MechanicMindset]

Good question, it’s not relative to a pressure measurement. We are just looking at the pattern

[@gypsysharky]

@@MechanicMindset thanks for the reply, but it will effect everything? If I go to high one peak will go into another section? Can you recommend any reading material that will clear this up?

[@michaelagnew7825]

Using crankcase pressure, can we accurately find where injector is firing in relation to tdc, without going in cylinder

[@MechanicMindset]

I suppose theoretically yes, you would have to use cam/crank sensor to reference and be sure exactly where TDC was. For example, the gap on the crank signal isn’t always exactly TDC. There are some other things to consider like pre injections and the flame spread time. Like your thinking!

[@michaelagnew7825]

@@MechanicMindset This test would be to check cam and crank in relation to tdc... indeed we would need to know manufacturers cranking degrees and do a little maths. Beats the hell out of removing plugs in diesels. Perhaps theres an option on dealers scan tools

[@teflon121]

Is the Pressure Waveform Overlays App available if using Pico on a Linux laptop?

[@MechanicMindset]

Not sure sorry

[@markhodge7485]

Could u not use a leak down testers

[@MechanicMindset]

Yeah sure, but some cylinders are a pain to remove a plug (diesels….even longer), and this set up could be quicker with practice with the scope ready to go on a diag stand. I’d say this test is about convenience but will require a bit of practice 👍

[@michaelrollins3979]

hey, could someone explain the overlay to me. How do you know which cylinder is doing what if he sets them in the middle of 3 and 4-such as at 6;46 in the video.... i get the colors but just dont get how to sync the waveform with the colorsfor all the cylinders. thanks

[@MechanicMindset]

I see what you mean. The horizontal position of the waveform has no significance. Some people actually keep it down blow out the way, but still lined up. The overlay just helps us identify what each cylinder is doing in that segment of the waveform. Let say we had a spike on the pulse sensors on the intake, we could assume an inlet valve was leaking. We would look at which cylinder was on a compression or power stroke (depending on engine state) to identify which cylinder is at fault

[@michaelrollins3979]

@@MechanicMindset ohh okay, that makes sense! Thanks for the reply. Love the videos, very helpful

[@MechanicMindset]

@@michaelrollins3979 The first time I looked at this overlay, it took me a while to figure it out 😂. Cheers!

[@harrys8068]

Personally would never of thought about using a oscilloscope for diagnosing engine mechanical faults. Just wondering what your opinion is for the pros and cons of this method compared to say Compression, leak down and a sniff tester

[@MechanicMindset]

It’s a great method. I think this could be quicker if your scope is always handy. I suppose the first measurement would be relative compression with the amp clamp. I would say this method is faster, but only if you have the knowledge of waveform analysis. Get some reference waveforms! This method checks all cylinders at the same time, where as cylinder leakage would have to be done individually. There are probable more but not sure. Some people would probably be more comfortable with the traditional method. Thanks👍

[@GrandePunto8V]

Compression has flaws too! You can get good number with closed (stuck) valves (exhaust). Using scope in the car diagnostics is a top level (mediocre clowns are afraid of it or think it's something "new" or inferior to "old-school" parts swapping). You can diagnose ALL possible mechanical faults using scope and proper probes, transducers etc.

[@joshuawood6588]

Would the ripples in the coolant test show the speed changes from the water pump following the speed changes of the crank shaft of a 4 stroke engine?

[@MechanicMindset]

Ahh yes, I like that answer! Makes sense 👍

[@joshuawood6588]

I just tried this test with a scion XB that has coolant standing in cylinder during pressure test but only show little differences in pulses while piston at top dead center? In my stall now

[@MechanicMindset]

@@joshuawood6588 Are you getting any gasses in the coolant system/over pressurising? Another trick I saw is to remove the cap tie a latex glove around the hole. It inflates if it’s blowing in to the cooling system

[@lawsonthursfield6950]

@@MechanicMindset good tip ... every day is a school day

[@joshuawood6588]

Yes found excessive pressure in coolant tank when removing cap. Customer declined any further repairs.

[@johnmwangi6291]

How do you manage to stay calm...🤔

[@MechanicMindset]

Haha, what do you think?

[@MechanicMindset]

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