How To Check The Compression Of An Engine

Scotty Kilmer, mechanic for the last 46 years and counting, shows how to check the compression pressure inside your engine. Engine compression test explained in detail.
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[@scottykilmer]

⬇️Things used in this video: 1. Compression Tester: amzn.to/2z13CaC 2. Ratchet and socket set: amzn.to/2inoxOY 3. Mechanic’s Tool Set: amzn.to/2Bzmccg 4. Disposable Gloves: amzn.to/2zSRuxO 5. Common Sense 6. Full HD Camera: amzn.to/2AvoEk7 7. My computer for editing / uploading: amzn.to/2i2sKYz 8. Video editing software: amzn.to/2jv5Fhf 9. Thumbnail software: amzn.to/2k7tz6C 🛠Check out my Garage to see what I use every day and highly recommend: www.amazon.com/shop/scottykilmer 👉Follow me on Instagram for the latest news, funnies, and exclusive info / pics: goo.gl/ohy2cA

[@MB-nl3ss]

What could be causing my car to smoke when it’s cold started?

[@jarvisparker8738]

@@MB-nl3ss water and condensation on exhaust it’s normal for cars to do that on cold start

[@timothydaschel]

You seriously make learning fun Scotty. The first video I watched of yours was "Replacing A Clutch" and I couldn't stop laughing. I have never seen somebody with so much enthusiasm while working as hard as you do. I am leaving for the U.S. Navy this September 11'th for the (AM) Aviation Mechanic program and want to thank you for the knowledge and mechanical comprehension you have given me for the past few years and that every time an F-18 takes off, it has a piece of you with it. -Tim

[@braki_1966]

Sir...thank you. Because of you I’ve learned a lot on my own. Keeps doing what you’re doing there’s a lot of people w/o dads out there or no one to teach em.

[@DcPwnsify]

How do I warm up my engine, if it doesn't start?

[@countryfella94]

Torch it!

[@moonyachti]

Break fluid in the intake if it starts change your fuel injectors 😷

[@jadelynn375]

Then do the air compressor method.

[@leomontaefeltus90]

U need a new engine happened with me

[@HandymanSam]

You give it a blanket and hot chocolate

[@scottykilmer]

you can disconnect the ignition system and remove the fuel pump fuse if you want to be really safety conscious. more than 15 percent diff is bad. No, you don't have to open throttle, just take readings in the same manner for all cylinders. Wet test is done to see if piston rings are worn, pressure goes up on wet testing if they are

[@scottykilmer]

Yes, warm it up first, then pull the plugs. Scotty Kilmer

[@scottykilmer]

@petisze as long as you do the same each time, you can leave the throttle open or closed to get accurate readings. Cranking that short time will not kill coils,only if you did it for many minutes on end. Scotty

[@chrispurse3931]

Thanks that was the answer I was looking for.

[@scottykilmer]

As I said, the actual pressure readings vary widely with gauges, so you measure the difference in pressure, and if one cylinder is more than 15 percent different than the others, that cylinder is worn inside. the actual pressure inside any engine varies widely, depending upon the outside temperature, the barometric pressure that day, the humidity, and the condition of the engine. And new engines have higher pressures that older worn engines. Scotty Kilmer

[@scottykilmer]

Since they spark plugs are all removed, any fuel will just be pushed out the empty holes. If you're worried about safety, doing the test in an enclosed area (unlike my test which was done outside), you can remove the fuel pump fuse. Scotty Kilmer

[@mypointofblue5260]

Just learned something new with my dad’s old tools! Thanks for sharing!

[@scottykilmer]

they are worn, but not totally if it runs good enough. I've seen them run years that way.If you like my car help, be sure to watch my live car talk show every saturday morning at 10 AM CST on google events. Just go to my scotty kilmer channel on youtube saturday morning at 10, and click on the google plus icon on the top right corner. That takes you to the event where you can ask me questions Live. You do have to be a member of google plus, but that's free

[@Abiwrl]

Thank you Scotty! For all these years of great learning.

[@jonathan-emilypowell1962]

Your the man Scotty, Thanks for the great videos!

[@scottykilmer]

It sure is a good way of checking rings. You can also use a leak down pressure tester to do this, which I will make a video of sometime in the future. Scotty Kilmer

[@scottykilmer]

Just go to any auto parts stores, they all sell em. I got mine at harbor freight tools.

[@scottykilmer]

As long as you do it with the throttle closed, or the throttle opened, the readings will be accurate when comparing the cylinders to each other. You can do it with a closed or open throttle, as long as you check them all the same way. Scotty Kilmer

[@sethlowell5255]

Hey Scotty would you have to reset your check engine light after one of these tests?

[@tubagoo2them00n]

this made my day. i was gonna do this to my car and decided to watch this first and i have the same exact car he does in this video :O!!! 1990 toyota celica :P

[@BL00DRIDER]

CONVENIENT

[@8060ren]

Thank you for your patriotic service in the military , as well as being good at whats best on youtube. You are truely a righteous soul! Much love and health and prosperity Uncle kilmer . Cant wait for your next show.

[@scottykilmer]

that stuff's B.S. If engine is worn, you have to rebuild it.

[@scottykilmer]

@DcPwnsify then you just take the readings cold, and if they are really low, engine is damaged inside.

[@scottykilmer]

generally, digital read out gauges do not last long and have many problmes, I've tried out various ones and always went back to mechanical whenever possible

[@DaVe-dv3qs]

What I usually do, is remove the fuse for the fuel injectors before i do it, so that way i don't have a bunch of unburnt fuel running through my engine

[@nordicpride9708]

Completely unnecessary

[@MikeCC]

@@nordicpride9708 I always thought you had to disconnect the fuel system like that though. Can you explain?

[@13scott71]

@scottykilmer That sucks buddy,I had a compression test done at a local shop and,from what they said, it was the valves. I had the head machined and valves re-seated only to put it back together and have the run exactly the same. I should have just done the rings but now I will have to get another set of bolts and another head gasket. Thanks for replying back to me. Scott

[@scottykilmer]

Check to make sure your fuel injectors are firing, many times the crankshaft position sensor goes bad and you lose fuel injection pulse. NO pulse, no fuel gets sprayed into the engine. Just for kicks, spray some starting fluid in the air filter hole to see if it starts. If it does, you know you've lost fuel to the engine then for sure. Scotty Kilmer

[@scottykilmer]

Yes, those do work best and are safest, but you'll never get the adapter stuck IF you put a little engine oil on it first.

[@scottykilmer]

crank it over by hand 2 times, then recheck the cam marks

[@houseof240s9]

scotty hopefully before I die I get to meet you. you're so awesome!

[@scottykilmer]

you can if you want, but if the ignition system is disabled it can't start, and any gas put into the cylinders would just blow out the exhaust as engine is cranked.

[@camrin1989]

Hi Scotty, thanks for all your great videos they will help extend the life of my aging car. However, this method blew two of my ignition coils. There was a loud bang when cranking, I think a spark must have arced between the two coils and I had to replace them. I can see your car here doesn't have individual coils so is a little different but people should know it's really important to disconnect these. All the best.

[@moonlalune8003]

very basic and step by step. Just right, thank you sir

[@chetvaldes]

I agree with you, streetfires, and it's usually easy enough to pull a connector off the coil to disable it.

[@scottykilmer]

Yes, on vehicles that have single ignition coils. And if you have multiple coil on plugs, just unplug them all when doing the test. Scotty

[@scottykilmer]

Well, I used to do a segment called "Crank It Up" and was REALLY tempted to add some porn to the car repair advice. But I never did. Scotty Kilmer

[@scottykilmer]

As I've already said, it doesn't matter if you have the throttle open or closed, as long as you do all the tests either open or closed. What you care about is the difference in pressure in the cylinders as I show in the video, NOT the actual pressure reading itself, which is not all that accurate. scotty kilmer

[@scottykilmer]

@fullvibe87 Diesel engines are Cows to do compression tests on. You need special tools, and have to remove each glow plug to check the pressure. That can be a royal pain. Scotty

[@scottykilmer]

@imautuber444 THERE are MANY ways to do a compression test, and as long as you are consistent and do them all the same, throttle open or closed, it does not matter how you do it, as it's the difference in cylinder pressure that counts in this test. BUT, yes, if you want the actual highest readings, you would do all that. Plus you would do a cylinder leak down tests with a different gauge, but that's a bit too complex for the average guy which is what this video is for. Scotty

[@scottykilmer]

@rockpetrad could be valves are too tight, yes. But more often it's a problem like cracked head gasket or worn piston rings. Scotty

[@alabamaman1]

Scotty for President

[@scottykilmer]

this is my indoor voice, I'm half deaf from fighting machines 44 years.

[@murkthebul6197]

Yup we still watch this 13 years later 🎉😂

[@scottykilmer]

@331lilcoupe It varies widely, which is why they tell you to compare the pressures on the gauge, not depend on the actual reading. Plus the pressure gauges are not all that accurate in terms of actual pressure. Scotty

[@scottykilmer]

@21mejia25 you can do it any way you want. As long as you do it the same for all cylinders. it's the difference between readings that counts mainly, not the actual readings, as those gauges aren't all that accurate to begin with when it comes to actual pressure

[@scottykilmer]

@sicktj No, the gauges are very inaccurate as to actual pressure, depends too much on the temp outside, the baro pressure, the engine temp, etc. It's the difference that really means something. Scotty

[@scottykilmer]

Yes, many auto parts stores will do that so their customers can do a job themselves and buy parts from them, rather than go somewhere else. Not a bad business decision really. Scotty Kilmer

[@scottykilmer]

if it will fit in the hole it will, try it and see. If it's just a push down tester, you push it down while another cranks the engine over

[@scottykilmer]

@TutorialTelevision they may not start up, they may run poorly, they may backfire or burn lots of oil.

[@scottykilmer]

I keep em sweet and short, that's why 19 million people have watched em so far

[@LilRedOne85]

Oh okay, gotta warm up the engine a few times!!! Thank you! 👻🔥

[@justindavis1192]

An Oldie but a Goodie. Thanks as always.

[@scottykilmer]

@BadAzzR3dn3k major, in most cases requiring rebuilding the engine or at least replacing the head gasket.

[@scottykilmer]

worn out engines often do that. Do a cold compression test of the engine, give me the readings

[@crowxrsmvsx]

Hi Scotty, I noticed in this video you did not disable the the ignition system. Is that something that needs to be done?

[@scottykilmer]

no, if the other cylinders start up and run, you would get an even more accurate reading on the one you were doing

[@supercocaso]

Thank you Scotty for the super quick response. And I did a dried and wet compression test it was good,and I pulled the coils with the spark plugs on and I cranked the engine and I see spark on the spark plug. Car smells like is running rich on fuel and spark plugs look wet. Thinking on checking the camshaft. No more ideas . Thank you for your help

[@scottykilmer]

@topgrain Yes, if you want to be ultra cautious, do this. Scotty

[@scottykilmer]

They do, but it's built into the distributor, so you'd have to replace the distributor to replace the sensor. That's what determines injector firing on that engine set up. And put a noid light on the injectors to see if they are firing (the light will flash if they are.) "Scotty Kilmer

[@PRCpower]

Best video. This guy is good.

[@aalsagr33]

Scotty, you are so kind to give you helpful advice to everyone. Your videos are nice and very clear thanks.

[@scottykilmer]

@xswsxcde you can, but the valves are opening and closing and this short time period it won't hurt anything

[@scottykilmer]

@Andrexthepuppy It could, but normally that's worn piston rings inside the engine allowing pressure to build up inside the crankcase. Scotty Kilmer

[@adrylena51]

Thanks a lot for your videos Scotty. You are one of the best .

[@llaponte62]

Thanks Scotty, you just saved my day!

[@kingdombarbershop1900]

Scotty you the best , you provide clear easy to follow info and even better you truly cheered me up with your presentation , specially your trunk appearance lmao, god bless

[@scottykilmer]

You can if you want, that's merely a safety issue of tiny amounts of fuel coming out the spark plug holes IF you are working inside a closed building. I work outside in the open air, so it doesn't matter there. Scotty Kilmer

[@kevincdano7896]

@scottyKilmer you are the best at explaining! God bless you

[@scottykilmer]

If you like my car help, be sure to watch my live car talk show every saturday morning at 10 AM CST on google events. I answer your car questions LIVE there. Just go to my scotty kilmer channel on youtube saturday morning at 10, and click on the google plus icon on the top right corner. That takes you to the event. You do have to be a member of google plus to ask questions, so join up, it’s all Free.

[@scottykilmer]

@DaBossk Well, they are all close, which is good. But 115 isn't very much pressure, though in an older engine if it runs OK, it will last a while that way. Scotty

[@atf-2229]

I would bet my entire life savings if Scotty and my grandpa ever were in a room together they would be best friends within 10 minutes

[@viisteist1363]

u have to remove power to the distributor and fuel pump too, plus press the gas pedal to the floor to open the throttle

[@scottykilmer]

sure, you remove the glow plugs and put a special compression adaptor in those holes to measure it

[@scottykilmer]

yes, an indirect way of using an oscilliscope and graphing the cranking voltage can be used, but it is not as accurate.

[@scottykilmer]

If you have a cylinder with really low pressure compared to the others, you would have to tear the engine apart and see what was broken inside, like bad valves or worn piston rings. Scotty Kilmer

[@romansten9]

Can't do it on a "warm" engine, I'm working on it and have the carb off! But it will be just fine cold.

[@e.s.l5861]

I really like these old videos

[@Kevinmaxtor]

Scotty nice 5th gen celica, i got one myself with the base 1.6L engine, great car especially now with gas prices up.

[@MrSTANGlover]

Mr. Kilmer! I love your videos! hahaa! I'm as hyped up as you are about cars! Thank you for all the knowledge.

[@scottykilmer]

@munirtalic get the whole engine, repairing them correctly costs many thousands. Scotty

[@chaconmcfly]

I love this guy's videos. He is a really good teacher and also he makes me laugh. Love the tips and goes straight to the point. Thanks boss

[@mikephillips6362]

Scotty, Thanks for the great videos. Your vids are to the point and without information we don't need. Thank ya for being so dependable.

[@scottykilmer]

@Infinitrium If you're careful, you can take it out of a warm engine. Just don't overtighten stuff and put some anti sieze lube on the plugs before putting em back in. Scotty

[@scottykilmer]

@13scott71 then the cylinder is leaking, losing pressure, normally bad comp rings. Scotty

[@scottykilmer]

do a compression test, cause either bad valves cause backfiring, or bad ignition systems firing wrong, or leaking fuel injectors. So pressure test to check the valves first

[@mitmaks]

You want to hold throttle to the floor when cranking, right?

[@scottykilmer]

Yea, they're really comfy. SAS gloves rule. Scotty Kilmer

[@kyttingirl]

Thanks so much, I now know how to check out things on my restore project. Your videos are a tremendous help!

[@LemuelDunleavy]

"Stay tuned" no pun intended.

[@mk3supra420]

Great video i needed to show the wife how to do this, due to my arm being broken and i watched about 6 videos and i was like nope nope nope u dont need to learn anything from these idiots and then boom ure video pops up and i couldent have explained it better myself, great video bud!

[@shawnreed6085]

I consider this a classic now

[@hankhill3417]

Imagine kids being taught this in school instead of the nonsense

[@scottykilmer]

you can do a compression test on any engine, hot or cold. do that first, cause if it's bad, no sense going any further

[@scottykilmer]

that pressure is not bad, but I'm always leery of guys selling used engines. why are they selling it? If it's pulled from the car already that's rather suspicious

[@scottykilmer]

@jarmchairpilot1 Yep, they only get tight by the valves or seats breaking down, with normal wear they get looser. Scotty

[@dragata1]

@TRcustomengineering the briggs engine block had cracks everywhere and the gaskets i couldnt find so i bought JB weld and used it as a sealer and gaskets its working GREAT

[@scottykilmer]

@Artyfil Sure, just make sure there isn't a big difference in them, and that they all aren't REALLY low pressure of an engine that's just plain worn out. Scotty

[@yr4137]

Thank, you Scotty for your very clear video.

[@scottykilmer]

@Andrexthepuppy Sometimes it will do that, but not always. Scotty

[@scottykilmer]

you remove the glow plugs and test compression in those holes

[@DanielMorilha]

I like how Scotty gets out of the trunk :-) on a side note didn't realize he had the channel for so long. Lucky Scotty youtube survived all of the ups and downs of the internet, if he had betted on Yahoo Answers for example, none of this great content would be available ;-)

[@dragata1]

@SCBianchi yea but jb weld leaks after a long time so i went back to the gaskest but this time i put jb weld and the gaskets on and better compretion and i put a little around the spark plug to make a perfect seal

[@mr7confused]

Wow that was fast!! The first video I watched took forever!

[@RobertGary1]

Intereting. Thanks. I've also noticed that it sometimes takes cranking the car several times to get the top PSI. Otherrwise I can get large differences between cylinders. Not sure if its my tool or not but it seems to peak sooner with the throttle open.