Compression Test help on LS3 - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

jwatty · 11-15-2019, 06:29 PM

I'm trying to do a compression test on my 2010 Camaro 2SS. I have followed all the directions in the Haynes Repair Manual.

-Removed Ignition Coil Packs
-Removed all spark plugs
-Removed air intake from throttle body and blocked TB wide open
-Removed the fuse for the ignition system (later questions)
-Removed the fuse for the fuel pump relay (after searching for forever, this was in the trunk passenger side)
-Installed a compression gauge in the spark plug hole

-I added this one myself, but I also removed the odd/even fuel injector fuses for the first attempt. When it didn't work, I went back to what the book said and placed them back in.

When I go to crank the engine, nothing happens. It doesn't even try to turn over. The only thing I'm not sure on is which ignition fuses to pull. I first tried fuses:

#15 IGN (5A)
#20 ECM/IGN (15A)
#9 INJ EVEN (20A)
#10 INJ ODD (20A)

https://www.camaro5.com/forums/attac...1&d=1573863452

After that, I tried with #9 and #10 back in. After that, all sorts of combo's.

I should note that I was able to start it before I took everything above off. The only thing that changed was that I had to take the battery out of the trunk and recharge it. Battery is holding its charge at 12.4v.

What am I missing?

G8One2 · 11-15-2019, 06:58 PM

Put the ECM fuse back in. It needs to see ignition power to turn it on. Once the ECM is powered, it will send a start command to the starter relay. The better way to do it, would be to use a jumper tool that has a button on it, attached to the starter solenoid. Use the button instead of the vehicles ignition. This way, you dont have to worry about puling any fuses to stop fueling because the key isnt needed and the ingition wont be on. Also, you should be doing a compression and leakdown test after the vehicle has reached normal operating temp. Use gloves to remove the spark plugs and install the tester.

One of these..... https://www.harborfreight.com/12-vol...tch-35448.html

jwatty · 11-15-2019, 08:00 PM

Thanks for your reply. I put the ECM fuse back in and it still wouldn't turn over. I like your idea of jumping the starter and plan to do that first thing tomorrow morning. That will make it a whole lot easier to watch the gauge as well.

G8One2 · 11-15-2019, 08:08 PM

Get the car back running. Get it warmed up to normal operating temp. The first pulse on the compression gauge should immediatly jump to 90psi or higher. If it doesn't, I would perform a leakdwon test to try and narrow it down some.

G8One2 · 11-15-2019, 08:10 PM

Also, using the tool, you won't need to turn the key on, so you will never get any fuel in the cylinders, or spark.

jwatty · 11-15-2019, 08:27 PM

I believe I have a bad lifter. It is making a ticking noise. How important is it to get the vehicle to normal operating temp? Would a bad lifter give horrible compression results regardless of temp?

G8One2 · 11-15-2019, 08:37 PM

You can do a cold test, it just won't show accurate pressure readings. Cold engines will read a lower pressure than that of a hot engine.

G8One2 · 11-15-2019, 08:42 PM

A noisy lifter usually won't show in a compression test unless you have bigger issues and broke parts

jwatty · 11-15-2019, 09:59 PM

Thank you for sharing your knowledge. I guess I should share why I'm doing this for a better diagnosis. I was driving my car down the highway and missed a down shift while passing. About a 1/2 a mile later, my car began to shake and I got the stabilitrak error on my dash. It felt like I had popped a tire so I pulled over to the shoulder and coasted down an off ramp to flat land. Once I slowed down enough, the engine just killed over. I can still run it, but it's rough and not drive able. Has a feint ticking noise. Throwing out P0300 code. About 2 weeks before this, I heard a chirping noise from time to time coming from engine. Oil pressure is fine. Fuel pump is working. I changed out spark plugs/wires. Changed out the MAF sensor. Tomorrow I plan to finish the compression test and if I can rent a leak down test, I'll do that too.

Camaro__ss · 11-15-2019, 11:59 PM

Sounds bad. Hope the engine isn’t locked up. Can you turn it over using the crank bolt?

TommyTheCat · 11-16-2019, 10:24 AM

On Chevys 2010+ you don't need to do a lot of this... simply take out the plugs on the cylinders you want to test, hook up the compression tester to a cylinder, hold the gas pedal all the way down to the floor and crank. If you don't believe me, try to start you car in normal conditions with the pedal down and it will not start, just crank. GM decided to disable fuel/spark with the pedal all the way down, makes for any easy compression test on newer GMs.

Also get a battery charger on the car if you are testing compression on more than a couple cylinders. Doing it cold will give you lower compression, but you are just trying to see if one cylinder is lower than average anyways right?

To be fair I haven't done this on the SS so you can disconnect the coils just to be sure, since most GMs have coil-on-plug, but if you try it with the engine in normal condition it will verify for you whether this trick will work or not

cheyndixon · 04-10-2022, 03:36 PM

so i don’t have to disconnect coil packs or any fuses before i crank the motor to test compression? just hold the throtte wide open?

1JEWLDSSRS · 04-11-2022, 08:56 AM

Yes sir...

04-11-2022, 08:56 AM	#13
1JEWLDSSRS Drives: 2011 SS-RS Join Date: May 2011 Location: FLORIDA Posts: 11,442	Yes sir... __________________ TSP STAGE 3 CAM,231/246 @112 LSA 614/641 LIFT, CIRCLE D 5C-4200-4500 CONVERTER,LOD INTAKE.CORSA EXHAUST. DSS 1 PC DS. PEGASUS SOLID CRADLE MOUNTS. 486RWHP/475RWTQ.LOTS MORE.

11-15-2019, 06:29 PM	#1
jwatty Drives: 2010 Camaro 2SS Join Date: Nov 2019 Location: U.S. Posts: 4	Compression Test help on LS3 I'm trying to do a compression test on my 2010 Camaro 2SS. I have followed all the directions in the Haynes Repair Manual. -Removed Ignition Coil Packs -Removed all spark plugs -Removed air intake from throttle body and blocked TB wide open -Removed the fuse for the ignition system (later questions) -Removed the fuse for the fuel pump relay (after searching for forever, this was in the trunk passenger side) -Installed a compression gauge in the spark plug hole -I added this one myself, but I also removed the odd/even fuel injector fuses for the first attempt. When it didn't work, I went back to what the book said and placed them back in. When I go to crank the engine, nothing happens. It doesn't even try to turn over. The only thing I'm not sure on is which ignition fuses to pull. I first tried fuses: #15 IGN (5A) #20 ECM/IGN (15A) #9 INJ EVEN (20A) #10 INJ ODD (20A) https://www.camaro5.com/forums/attac...1&d=1573863452 After that, I tried with #9 and #10 back in. After that, all sorts of combo's. I should note that I was able to start it before I took everything above off. The only thing that changed was that I had to take the battery out of the trunk and recharge it. Battery is holding its charge at 12.4v. What am I missing? Attached Images

11-15-2019, 06:58 PM	#2
G8One2 Drives: 2014 Camaro 2SS Join Date: Feb 2015 Location: Metro Detroit Posts: 492	Put the ECM fuse back in. It needs to see ignition power to turn it on. Once the ECM is powered, it will send a start command to the starter relay. The better way to do it, would be to use a jumper tool that has a button on it, attached to the starter solenoid. Use the button instead of the vehicles ignition. This way, you dont have to worry about puling any fuses to stop fueling because the key isnt needed and the ingition wont be on. Also, you should be doing a compression and leakdown test after the vehicle has reached normal operating temp. Use gloves to remove the spark plugs and install the tester. One of these..... https://www.harborfreight.com/12-vol...tch-35448.html

11-15-2019, 08:00 PM	#3
jwatty Drives: 2010 Camaro 2SS Join Date: Nov 2019 Location: U.S. Posts: 4	Thanks for your reply. I put the ECM fuse back in and it still wouldn't turn over. I like your idea of jumping the starter and plan to do that first thing tomorrow morning. That will make it a whole lot easier to watch the gauge as well.

11-15-2019, 08:08 PM	#4
G8One2 Drives: 2014 Camaro 2SS Join Date: Feb 2015 Location: Metro Detroit Posts: 492	Get the car back running. Get it warmed up to normal operating temp. The first pulse on the compression gauge should immediatly jump to 90psi or higher. If it doesn't, I would perform a leakdwon test to try and narrow it down some.

11-15-2019, 08:10 PM	#5
G8One2 Drives: 2014 Camaro 2SS Join Date: Feb 2015 Location: Metro Detroit Posts: 492	Also, using the tool, you won't need to turn the key on, so you will never get any fuel in the cylinders, or spark.

11-15-2019, 08:27 PM	#6
jwatty Drives: 2010 Camaro 2SS Join Date: Nov 2019 Location: U.S. Posts: 4	I believe I have a bad lifter. It is making a ticking noise. How important is it to get the vehicle to normal operating temp? Would a bad lifter give horrible compression results regardless of temp?

11-15-2019, 08:37 PM	#7
G8One2 Drives: 2014 Camaro 2SS Join Date: Feb 2015 Location: Metro Detroit Posts: 492	You can do a cold test, it just won't show accurate pressure readings. Cold engines will read a lower pressure than that of a hot engine.

11-15-2019, 08:42 PM	#8
G8One2 Drives: 2014 Camaro 2SS Join Date: Feb 2015 Location: Metro Detroit Posts: 492	A noisy lifter usually won't show in a compression test unless you have bigger issues and broke parts

11-15-2019, 09:59 PM	#9
jwatty Drives: 2010 Camaro 2SS Join Date: Nov 2019 Location: U.S. Posts: 4	Thank you for sharing your knowledge. I guess I should share why I'm doing this for a better diagnosis. I was driving my car down the highway and missed a down shift while passing. About a 1/2 a mile later, my car began to shake and I got the stabilitrak error on my dash. It felt like I had popped a tire so I pulled over to the shoulder and coasted down an off ramp to flat land. Once I slowed down enough, the engine just killed over. I can still run it, but it's rough and not drive able. Has a feint ticking noise. Throwing out P0300 code. About 2 weeks before this, I heard a chirping noise from time to time coming from engine. Oil pressure is fine. Fuel pump is working. I changed out spark plugs/wires. Changed out the MAF sensor. Tomorrow I plan to finish the compression test and if I can rent a leak down test, I'll do that too.

11-15-2019, 11:59 PM	#10
Camaro__ss Drives: 2013 L99 Join Date: Jan 2019 Location: San Antonio TX Posts: 185	Sounds bad. Hope the engine isn’t locked up. Can you turn it over using the crank bolt?

11-16-2019, 10:24 AM	#11
TommyTheCat SHKE BKE Drives: 2013 Camaro Join Date: May 2014 Location: SoCal Posts: 3,108	On Chevys 2010+ you don't need to do a lot of this... simply take out the plugs on the cylinders you want to test, hook up the compression tester to a cylinder, hold the gas pedal all the way down to the floor and crank. If you don't believe me, try to start you car in normal conditions with the pedal down and it will not start, just crank. GM decided to disable fuel/spark with the pedal all the way down, makes for any easy compression test on newer GMs. Also get a battery charger on the car if you are testing compression on more than a couple cylinders. Doing it cold will give you lower compression, but you are just trying to see if one cylinder is lower than average anyways right? To be fair I haven't done this on the SS so you can disconnect the coils just to be sure, since most GMs have coil-on-plug, but if you try it with the engine in normal condition it will verify for you whether this trick will work or not

04-10-2022, 03:36 PM	#12
cheyndixon Drives: 2010 2ss camaro Join Date: May 2021 Location: macon, michigan Posts: 2	so i don’t have to disconnect coil packs or any fuses before i crank the motor to test compression? just hold the throtte wide open?