LQ9 cranking compression
Thread Starter
Teching In
Joined: Apr 2010
Posts: 49
Likes: 0
LQ9 cranking compression Got a 2005 LQ9 with 110,00 miles from LKQ to start my conversion project. Threw it on engine stand and did a cranking compression test. 270 - 300 psi. WTH!!! I was expecting 190-210. My first thought is user error, but how could i screw up a cranking compression test? Is there something wrong with this engine? I am tempted to return it now. I don't want to install it and have it not work. Any thoughts?
Thanks
Thanks
Hydraulic lifters work with oil. If an engine has not run in a while and has been rotated a lot you can squeeze the oil out of the lifters. If the lifters are bled down, you will have an earlier intake valve close which increases dynamic compression.
Thread Starter
Teching In
Joined: Apr 2010
Posts: 49
Likes: 0
Sorry it took so long to retest the motor, but here are the results.
I first hooked up a mechanical oil pressure gauge. Spun the motor and no oil pressure. I did put oil in filter prior to screwing it on. So I spun the motor for 20 seconds four times and got 30 psi pressure while cranking. I then repeated the compression test and found 230-250 psi on all but number 8 which was 210. I did get another compression gauge and it read about the same as mine. I guess there was something to the theory of lifter leak down and higher dynamic compression as the compression is now down to what is expected.
I made a leak down tester (using a dampener plug 0.25"x0.040") and got 93-98% all cylinders but 7 and 8. They were 90%. Sounds reasonable right? I used a HF inspection camera to inspect the piston tops ( actually I was using it to ID TDC). and saw the apparent marks in the tops of pistons 7 and 8. Is that my imagination or does that look like the valves kissed the piston?
The leak down and compression tests are ok so should I be concerned? I know that this is a salvage yard motor with 110K miles. I don't want to take it back to LKQ and ask for a different motor unless needed. I most likely won't be able to start the motor til spring to see how well it runs.
Thoughts?
I first hooked up a mechanical oil pressure gauge. Spun the motor and no oil pressure. I did put oil in filter prior to screwing it on. So I spun the motor for 20 seconds four times and got 30 psi pressure while cranking. I then repeated the compression test and found 230-250 psi on all but number 8 which was 210. I did get another compression gauge and it read about the same as mine. I guess there was something to the theory of lifter leak down and higher dynamic compression as the compression is now down to what is expected.
I made a leak down tester (using a dampener plug 0.25"x0.040") and got 93-98% all cylinders but 7 and 8. They were 90%. Sounds reasonable right? I used a HF inspection camera to inspect the piston tops ( actually I was using it to ID TDC). and saw the apparent marks in the tops of pistons 7 and 8. Is that my imagination or does that look like the valves kissed the piston?
The leak down and compression tests are ok so should I be concerned? I know that this is a salvage yard motor with 110K miles. I don't want to take it back to LKQ and ask for a different motor unless needed. I most likely won't be able to start the motor til spring to see how well it runs.
Thoughts?
