I learned this in school but you explained it 10x better plus you dropped a diag jewel when you explained what the results of a wet compression test vs cranking compression test could mean.
There should be a Schrader valve (like the valve stem on your tire) in the hose. Someone (probably whoever rented it last) likely removed it. Without that valve, any pressure the engine builds will be gone as soon as the valves open, and you'll get a zero reading.
Sometimes it happens that the previous renter didnt report an issue with the tool, to avoid getting charged for it. That happened to me with a torque wrench at autozone. I went back and mentioned the issue and they gave me another that worked fine.
excellent video. i knew nothing about how to do this test, now thanks to you i know how to do it and alot more detail as well; like what could be causing low compression in cylinders. thanks for not talking sooo fast, like most others..and speaking clearly and to the point without a lot of unwanted music, drama etc. ..yoour an excellent teacher..actually a professor.
Absolutely excellent video. All information was incredibly useful and concise. It’s exactly what I needed. Only thing is I have a mechanical fuel pump, so removing a fuse won’t work on that one. Anyway, you have a new subscriber, as you are a great teacher
Looking at other TH-cam videos some of them say you make sure the enginer is warmed up before you do this test. That seems like sound advice as metal expands when warmer so it seems sense that it could effect compression.
Absolutely perfect, exactly the information I needed! I'm trying to figure out the cause of low compression on one cylinder, and am hoping it's just in need of a valve adjustment (common for the engine). If I can go get a $50 compression tester and use the oil trick to determine piston rings or valves...would be...just...amazing. I suppose it wouldn't tell me if the valves are wasted or just out of spec, though. Still, thank you!
Thank you sir. Before running a compression test, it's recommend to warm up the engine ( until it gets hot). And also keep some weight on the accelerator pedal while the engine is off ,this way the throttle plat stay fully opened, to allow more air entering the chamber combustion. If you have very Low pressure on two adjacent cylinders، specially 0 psi. That means, there a blown head gasket.
I think you forgot to mention about opening throttle body on newer cars and trying to do it with a warm car... allowing the metals to expand to closer to operating temps.
There's two schools there. If you warm the engine first, letting things have a chance to seal up, you're getting a reading at operation, yes but, if you do the test cold, you actually can find out what's worn or wearing. I want to know if the rings are just starting to wear or the valves are carboned up and need to be "blasted." Doing it with a hot engine just tends to mask the problems you're trying to find. I'm an ASE engine performance and drivability tech and I came up in the old school world of actually finding any mechanical issues rather than try to cover them up. An engine always gives up its secrets and runs the worst when it's cold... And that's when you find out what lays ahead. :)
Hi, Great Video. Question.?. I own a 1970 Chevy Impala with a 350engine. How do I stop the fuel from going into the carburetor.????. And I also have a HEI Distributor. Can you please let me know how.🙏🏽☹️
Disconnect the fuel inlet from carb, put a tube on it and put the other end into a portable gas tank (so you save that gas) As far as your distributor, disconnect the connector that leads into the HEI. This prevents any spark from being created.
I'am Your Newest Subscriber Great Videos . I Have A 95 S10 2.2 Liter With 5 Speed Manual Has Choptop Roof Hasent Ran In 11 Years I Wanta Get It Running Again Has Low Compression In A Few Cylinders
To calculate the compression pressure you need to multiple the compression ratio by atmospheric pressure then add the atmospheric pressure to your multiplied result eg if you have a compression ratio of 9 to 1 and a atmospheric pressure of 14.7, 9x14.7 =132.3 +14.7 =147 psi , also I would look up how to carry out a compression test properly
So if I stop the fuel and spark it should be okay to remove the exhaust manifold to get to those back three spark plugs when I'm doing this test, right? Cheers & thanks.
for the third kind of compression loss, smell the oil. if it smells like a marina, you've got work to do. that or grab your drink of choice and call your mechanic, trust me you'll need the drink.
Dylan, If you have a rubber hose somewhere ( AFTER THE PUMP ) crimp it off with vice grips & rubber hose over the teeth. Or disconnect the steel fuel line ( AFTER THE PUMP ) & add rubber hose to it ( WITH HOSE CLAMP ) then run it into a bucket.
What if the compression drops? Or does that matter? Mine read good at 150 but dropped very slowly like almost not noticeable. But did drop after a while
I did my first test on my Honda Ridgeline, but I think they are too high, 235 225 225 220 230 230, is that good???, I took out all the spark plugs, fuel pump relay, ignition fuse, ignition coils etc.
You are 100% correct. Always remove all the plugs, have a good battery to crank the motor and have your throttle wide open. Maybe Cooley thinks he knows, but doesn't really know.
@@jonhromeo6108 To me the most accurate way on a carbureted engine is simply to remove the carb intself. But as it may be a pain to do, unplug the the pump intake line fist. Then let the engine die. After that you can perform the test. Be sure that you maintain WOT and also that the cold start device would'nt mask the carb air intake during cranking operations. Best result if you remove the air filter. Cheers
Vaporised gas, can disturb results as gasoline has a tendency to wash the cylinder liners oil compound when no ignition occurs. Results may vary between a dry or a wet cylinder.
My car stopped when driving I think my timing belt slipped. My friend tried to push start it. Now it's reading no compression . Would push starting damage the valves?
Please explain more my brother!! My compression was a lot higher but all consistent with each other just after 5 compression strokes. And after the test The 5.2 will not start now. Did I f^__ something up.l disconnectied coil to safe place but not fuel?? Lost here my friend!! Montana Rick.
if I take out all the spark plugs start from cylinder 1 2 3 4 on my 91 Honda CRX without disconnecting anything else like the ignition system or pulling out fuel relay just taking out the spark plugs will I get an accurate reading?
The reading is accurate for that test condition. BUT please be AWARE that leaving the plugs out with everything else connected. Will mean the injectors squirting fuel, the pistons pushing that spray out of the engine in the mist of spark plugs doing what they do best, putting out a spark. With that in mind remember that gas spray and spark is usually a dangerous combination... ;-)
Sir I have a doubt. If the piston rings are damaged is it possible to burn engine oil already in engine . If it's happen the engine oil thus entered will act as a seal and will shows the compution pressure reading That will show when we pour some oil in it for sealing
Im scared.. I just bought an Engine, chasing a P0300 code. A friend said to do a compression test, but I'm scared to do it & find out if there is something internally damaged.
ok but using the compression tester you are using with no Shrader valve at the plug end will give you a incorrect reading as you are not correct in the swept volume of the cylinder. best compression tester is cp7828 with the scrader valve. .you will get low compression on that unit.
I would also open up the throttle body vanes to allow airflow into the engine. Make sure to undo this step before you put everything back together again and run it for real otherwise you won't be happy.
Hi , i think there is no need to remove the fuse for the Ignition , because i have to crank the engine using the ignition , right ? One more thing is that to Crank the engine it might discharge the Battery even if the battery is new so what should we do to avoid discharging the battery while doing compression test for all the cylinders ? thanks ..
![How To Perform a Compression Test - [EASY]](http://i.ytimg.com/vi/3VmmL0YAO14/mqdefault.jpg)
![How To Perform a Compression Test - [EASY]](/img/tr.png)
So concise yet covered everything. No blabbing, you know your stuff. I like it!
I learned this in school but you explained it 10x better plus you dropped a diag jewel when you explained what the results of a wet compression test vs cranking compression test could mean.
Rented Oreillys tester... got zero psi on all cylinders, drove back and went somwhere else on zero psi car....
I was about to go and rent the tool from them too lol thats why I was watching this video. guess I'm not going to anymore
There should be a Schrader valve (like the valve stem on your tire) in the hose. Someone (probably whoever rented it last) likely removed it. Without that valve, any pressure the engine builds will be gone as soon as the valves open, and you'll get a zero reading.
Sometimes it happens that the previous renter didnt report an issue with the tool, to avoid getting charged for it. That happened to me with a torque wrench at autozone. I went back and mentioned the issue and they gave me another that worked fine.
Couldn’t have been user error!! 😂
Tool was obviously broken
Short and sweet, nothing but the information i wanted and needed, thanks.
OMG so quick and well spoken with no babble... THANK YOU :)
Straight to the point. Exactly what I was looking for
Outstanding little video. Great way to introduce someone to compression testing basics…..
Outstanding hosting. Nice production quality too.
excellent video. i knew nothing about how to do this test, now thanks to you i know how to do it and alot more detail as well; like what could be causing low compression in cylinders. thanks for not talking sooo fast, like most others..and speaking clearly and to the point without a lot of unwanted music, drama etc. ..yoour an excellent teacher..actually a professor.
Exactly the style of information delivery we need more of.
Absolutely excellent video. All information was incredibly useful and concise. It’s exactly what I needed. Only thing is I have a mechanical fuel pump, so removing a fuse won’t work on that one. Anyway, you have a new subscriber, as you are a great teacher
Great information, and great production and editing. Thanks for keeping it concise!
Looking at other TH-cam videos some of them say you make sure the enginer is warmed up before you do this test. That seems like sound advice as metal expands when warmer so it seems sense that it could effect compression.
Thank you for this very simple and clear explanation of compression testing
"Your engine is all about cylinders"
Me with 13b: I already failed that one
I'm so pleased that you spoke about the 'wet' compression test. So many 'experts' don't know about that one.
I’m high and happy…
not me.. my car is misfiring and thats why im here.
@@lilgagey3889😢
Me too bud, me too
Absolutely perfect, exactly the information I needed! I'm trying to figure out the cause of low compression on one cylinder, and am hoping it's just in need of a valve adjustment (common for the engine). If I can go get a $50 compression tester and use the oil trick to determine piston rings or valves...would be...just...amazing. I suppose it wouldn't tell me if the valves are wasted or just out of spec, though. Still, thank you!
Clearest information and tutorial. Just what I needed
Thank you sir.
Before running a compression test, it's recommend to warm up the engine ( until it gets hot).
And also keep some weight on the accelerator pedal while the engine is off ,this way the throttle plat stay fully opened, to allow more air entering the chamber combustion.
If you have very Low pressure on two adjacent cylinders، specially 0 psi.
That means, there a blown head gasket.
Excellent excellent video; great communication skills too; very informative !!!!!!!
I think you forgot to mention about opening throttle body on newer cars and trying to do it with a warm car... allowing the metals to expand to closer to operating temps.
There's two schools there. If you warm the engine first, letting things have a chance to seal up, you're getting a reading at operation, yes but, if you do the test cold, you actually can find out what's worn or wearing. I want to know if the rings are just starting to wear or the valves are carboned up and need to be "blasted."
Doing it with a hot engine just tends to mask the problems you're trying to find. I'm an ASE engine performance and drivability tech and I came up in the old school world of actually finding any mechanical issues rather than try to cover them up. An engine always gives up its secrets and runs the worst when it's cold... And that's when you find out what lays ahead. :)
Pressure test should be done on cold engines.
On newer cars (ie after 1990) you can generally hold the accelerator and turn the key rather than disconnecting fuel and coils
why holding the accelerator?
Clear flood mode, prevents car from starting
Hi, Great Video. Question.?. I own a 1970 Chevy Impala with a 350engine. How do I stop the fuel from going into the carburetor.????. And I also have a HEI Distributor. Can you please let me know how.🙏🏽☹️
Disconnect the fuel inlet from carb, put a tube on it and put the other end into a portable gas tank (so you save that gas)
As far as your distributor, disconnect the connector that leads into the HEI. This prevents any spark from being created.
Cool Thanks 👍
Cooley Nails it again!
Top notch professional tutorial!
This was really to the point. Very informative!
Excellent video Brian!
Straight forward. No bs. Thanks
I'am Your Newest Subscriber Great Videos . I Have A 95 S10 2.2 Liter With 5 Speed Manual Has Choptop Roof Hasent Ran In 11 Years I Wanta Get It Running Again Has Low Compression In A Few Cylinders
Informative and straight to the point.
What an excellent video on the subject!
I agree, short and sweet!
Awesome quick video!
excellant video please don't delete it
Well done Cooley
what is a good place to buy a used or rebuilt engine i am in sacramento ca
Best video so far 😊👍
Awesome....to the point.....no quirky comments or trying to be funny....
Awesome Video. Very Informative.
Loving the more cooley vids!
my toyota corolla 2014 model 1.3 Liter engine compression is 130 psi on each cylinder, is it good or not?
what should be the compression of the cruze 1.8 petrol engine??
my chevy has 11 bars for each cylinder
To calculate the compression pressure you need to multiple the compression ratio by atmospheric pressure then add the atmospheric pressure to your multiplied result eg if you have a compression ratio of 9 to 1 and a atmospheric pressure of 14.7, 9x14.7 =132.3 +14.7 =147 psi , also I would look up how to carry out a compression test properly
So if I stop the fuel and spark it should be okay to remove the exhaust manifold to get to those back three spark plugs when I'm doing this test, right? Cheers & thanks.
for the third kind of compression loss, smell the oil. if it smells like a marina, you've got work to do. that or grab your drink of choice and call your mechanic, trust me you'll need the drink.
Boy I should have grabbed the drink before bringing it to my mechanic, that hurt my wallet
@@professionalgenny5096 sorry to hear that.
@@professionalgenny5096 Oof, been there...
Novice question. I've got a 68 javelin running a mechanical fuel pump. What is the best way going about shutting off fuel supply? Thanks in advance
Dylan, If you have a rubber hose somewhere ( AFTER THE PUMP ) crimp it off with vice grips & rubber hose over the teeth. Or disconnect the steel fuel line ( AFTER THE PUMP ) & add rubber hose to it ( WITH HOSE CLAMP ) then run it into a bucket.
Please@@NoWr2Run
So how do you cutoff the fuel for an older carbureted vehicle?
"hope your cylinders are all high and happy!" 🤣
I hope I don't regret buying one off of Temu, but I'm still learning anyway.
Does the engine need to be warm ?
Thanks.
What if the compression drops? Or does that matter? Mine read good at 150 but dropped very slowly like almost not noticeable. But did drop after a while
Perfectly normal.
Good job
I did my first test on my Honda Ridgeline, but I think they are too high, 235 225 225 220 230 230, is that good???, I took out all the spark plugs, fuel pump relay, ignition fuse, ignition coils etc.
Does 3 in 1 oil work just fine to spray into the cylinder like he mentioned? Or does it have to be motor oil
3 month old comment but it has to be motor oil. You don’t want to contaminate the oil with solvents.
Warm engine, healthy battery, all spark plugs removed and wide open throttle during cranking are both required to perform a real accurate test to me.
You are 100% correct. Always remove all the plugs, have a good battery to crank the motor and have your throttle wide open. Maybe Cooley thinks he knows, but doesn't really know.
@@johnnybonacci7114 CORRECT, both of you, I also put a battery charger on my battery while performing the test. HE DOESN'T REALLY KNOW, LMAO.
On carburated motors do u take off mechanical fuel pump before test ? Or just leaave on and test ?
@@jonhromeo6108 To me the most accurate way on a carbureted engine is simply to remove the carb intself.
But as it may be a pain to do, unplug the the pump intake line fist. Then let the engine die.
After that you can perform the test.
Be sure that you maintain WOT and also that the cold start device would'nt mask the carb air intake during cranking operations.
Best result if you remove the air filter.
Cheers
Vaporised gas, can disturb results as gasoline has a tendency to wash the cylinder liners oil compound when no ignition occurs.
Results may vary between a dry or a wet cylinder.
Great video very clear
What if i actually kept the fuel pump on and start the engine to measure the pressure, is that ok?
That's ok if you remove the injectors cables, otherwise the catalytic converter won't like it.
The petrol will spray inside cylinder.
About how much oil to squirt in a cylinder ?
man! very well explained Thank's
Disabling the spark..is that the same as pulling out the COIL PACK?
Very good and informative video, thank you!
so if the pistons are bad and leak oil it will read high compression ? because already has its own oil
Thanks. Very helpful!
If its carburated does throttle need to be wide open?
Do you have to warm the engine up to do it?
So would an engine with 10.5 compression ratio yield higher numbers then an engine with 8.5 ?
Google what your particular engine is supposed to be. My honda is 220 across the board lol
My car stopped when driving I think my timing belt slipped. My friend tried to push start it. Now it's reading no compression . Would push starting damage the valves?
awesome one on one
You are right but if the top of the piston has carbon build up it will artificially raise the compression
Please explain more my brother!! My compression was a lot higher but all consistent with each other just after 5 compression strokes. And after the test The 5.2 will not start now. Did I f^__ something up.l disconnectied coil to safe place but not fuel?? Lost here my friend!! Montana Rick.
What year is this Cougar?
Fantastic!! Thank you!
Excellent
Thanks 🙏
how can i do it with a push start engine?
if I take out all the spark plugs start from cylinder 1 2 3 4 on my 91 Honda CRX without disconnecting anything else like the ignition system or pulling out fuel relay just taking out the spark plugs will I get an accurate reading?
The reading is accurate for that test condition. BUT please be AWARE that leaving the plugs out with everything else connected. Will mean the injectors squirting fuel, the pistons pushing that spray out of the engine in the mist of spark plugs doing what they do best, putting out a spark.
With that in mind remember that gas spray and spark is usually a dangerous combination... ;-)
Jesus Moya that will alter your compression reading slightly. Fuel doesn’t compress.
Just got a tester got the hood open and realized i left my tools in my buddies broke down van😂💀
Sir I have a doubt.
If the piston rings are damaged is it possible to burn engine oil already in engine .
If it's happen the engine oil thus entered will act as a seal and will shows the compution pressure reading
That will show when we pour some oil in it for sealing
very concise thanks!!!!!
great video :D
Im scared.. I just bought an Engine, chasing a P0300 code. A friend said to do a compression test, but I'm scared to do it & find out if there is something internally damaged.
Warm or cold test? Or doesn't it matter?
Okay how do U disconnect a quadjet please help
great vid
How to disable the fuel supply on a muscle car with a mechanical fuel pump?
What if the intake manifold is off?
informative. thanks
Muy bueno gracias
You have not mentioned the most important reading on the gauge...the reading of d 1st crank
thank you!
Thank you
ok but using the compression tester you are using with no Shrader valve at the plug end will give you a incorrect reading as you are not correct in the swept volume of the cylinder. best compression tester is cp7828 with the scrader valve. .you will get low compression on that unit.
Awesome , thanks
Veteran in automotive industry experience
You re a master
Thanks homie
I would also open up the throttle body vanes to allow airflow into the engine. Make sure to undo this step before you put everything back together again and run it for real otherwise you won't be happy.
Hi , i think there is no need to remove the fuse for the Ignition , because i have to crank the
engine using the ignition , right ?
One more thing is that to Crank the engine it might discharge the Battery even if the battery is new
so what should we do to avoid discharging the battery while doing compression test for all the
cylinders ? thanks ..
Lennox
have a back up battery or a battery charger. or boost/jumpstart it with another car.
Brilliant cheers
I can tell that man cares a lot about his watch
piston has to be at tdc as well