8g I4 compression testing
So you are thinking about doing a compression test on your engine before you add that new piece of HP to it? well you're in luck.
Disclaimer: please follow these instructions at your and your car's own risk, if after reading through the instructions you do not feel you can do the job then don't. I will not be responsible for any injury or damage to yourself or your vehicle.
That being said: When I did this to my 8g galant there was a fitting on the end of my compression gauge which got stuck inside a cylinder. I did not realize it until i went though two spark plugs and crushed them because i was able to still thread them in.
Tools:
Compression gauge = picked one up for $47.00
10 mm socket with socket wrench
spark plug socket (make sure that it has the rubber ring inside of it)
socket wrench with the longest extension you can get for it
**If you have a remote start that will be great, but not mandatory**
**also could be a good time to change spark plugs**
**specs are taken from two shop manuals**
**instructions from experience with my 8g***
note: I needed two different socket wrenches smaller one for the 10mm, and larger for spark plugs.
You want to try this with the engine at operating temp so go for a drive until engine is at norm come home and by the time you prep take a bathroom break and get some OJ you should be good to go.
1. First get a cloth or shop rag and clean around the coils on the top of the head to remove debris. I did not use any solvent or cleaner cause I did not want to accidentally have fluid leak into the cylinders, but the shop manual says use compressed air if you have it, i did not)
2. Next, (looking at the engine facing the car cabin from left to right) cylinder 2 and cylinder 4 have coil packs with electrical connectors. Unplug these connectors and face them away from the head just in case fluid of debris flies up. 2 is connected to 3 and 1 is connected to 4, i just kept them together and made sure not to pull on the chords.
3. before you remove the coil boots and remove all the spark plugs, open up the fuse box in the engine bay and remove the fuel pump relay. one of the two large blocks closest to the front of the car, you want to remove the one on the right closest to the driver fender
4. remove the coils by twisting the boots side to side then pulling them up, do not pull the chord excessively.
5. now use you spark plug socket to remove the spark plugs. If sure most of you have done this, but if you have not, the rubber o ring inside the socket will hold the plug in so it can be lifted out.
6. as I removed each plug I placed a clean(ish) shop towel over the open cylinder so nothing would accidentally fall in. I only allowed the cylinders I was working in to be open to the air.
7. Now, with all the plugs removed keep the shop rag over all four cylinders
and:
a. if you do not have a remote start, have someone crank the engine while you hold the throttle wide open. the car will try to start and fail.
b. if you have a remote start then hold the throttle wide open and use the remote starter. my starter tried three times then would quit so I just let it run its course.
this step clean out any debris in the cylinders so that it will not clog you compression tester. oil and carbon build up may spray onto you shop towel. I don't know if anyone has info about it but check your old spark plugs for sings of engine condition.
8. thread in the compression tester into the cylinder you want to test keeping the others covered. with tester installed and zeroed, and holding the throttle wide open, start the engine and crank to compression about 7 times. record the ma reading on the gauge. Do the same for all cylinders.
9. compare your recordings with galant specs of i think its 139 psi to 185psi
10. after all readings are done make sure that the difference between adjacent cylinders is not more than 14psi difference.
11. if there is a cylinder that is outside of the 14 psi difference or does not met the range of 139 to 185 psi pour a small amount of oil maybe a cap full into that cylinder's hole, reattach tester, and test again.
***remember to zero the gauge before re-using***
12.
a. if the pressure increases after adding oil problem is worn or damaged piston ring or cylinder surface or both.
b. if pressure does not rise then there is a gasket leak or bad valve seat
13. when done install spark plugs, i choose to remove the rubber o ring from the spark plug socket so that the ring does not stay stuck to the plug when I pull the plug out. just let the spark plug in as deep as you can with your hands then let it fall to resist impact. I take the extension with plug socket still attached and put it into the cylinder and turn it until the spark plug catches and eases in until I cant turn it by hand anymore. Only then did i attach the socket wrench and torque down to torque. do the same for all plugs.
** please do not rush this process take your time**
14. place coils back on, I find that coil 1 never wants to seat properly, push on the boot harder and it will flatten eventually. you may sometimes have to pull the chord out so excess is not inside the cylinder. once that is done attach the clips to the coil packs.
15. lastly don't be like me and try to start the car before putting the fuel pump relay back in, you might wonder why the car wont turn over but won't stop trying to start.
the manual is talking about carbon deposits can cause the cylinder pressure to be unusually high. If you want to know how to get rid of carbon build up, I hear sea foam works, but I have only used b12 and I was surprised with how well it worked.
Done. feel free to post any questions or screw ups on my end. thanks
