No compression when engine is cold

MASE MOUSSA

MEMBER
2000 MERCEDES BENZ C200
2.0L
4 CYL
2WD
AUTOMATIC
200,000 MILES

When starting the crank in the morning it has no compression in 3 cylinders 1-2-4 and very low compression in cylinder 3 about 50 psi. If you keep cranking the car for about 2 minutes and get it warmed up it will start, but runs really rough. Once you run it for a while and it heats up more you turn it off and turn it back on and it will run perfect. No misfire, no noise it will run very smooth and it will be fine. If you turn off and start again but if you let it sit long enough 2-3 hours you will start with the same problem again. Has anyone come across this issue? Suggestions please.

Wednesday, November 20th, 2019 AT 4:50 PM

1 Reply

JACOBANDNICKOLAS

MECHANIC
110,097 POSTS

Hi,

When steel heats up, it expands. So, I would suggest performing a wet compression. When this is done, you add about a table spoon of motor oil into the cylinder being tested to see if compression increases. If it does, the rings are bad. If it doesn't, then it is most likely a valve issue or head gasket issue.

Additionally, if you have a fuel injector leaking, the fuel can wash oil away from the cylinder walls causing lower compression.

At this point, I suggest performing a wet compression test to see if the low cylinder compression increases. Do this when it is cold.

Do this and let me know what you find.

Joe

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Wednesday, November 20th, 2019 AT 9:08 PM