Hi guys, how does one check compression on an m271 engine and how/what/where to disconnect so that the car doesnt start.

thanks!

 

All plugs out. Move coil on plug leads away from the plug holes. The AF ratio is unlikely to cause ignition but keep them out of where they can throw a spark to earth.

Apply WOT (wide open throttle). Place compression tester in each plug hole. Crank until max pressure is recorded on the gauge & record cylinder by cylinder. Do the dry first. Then give each cylinder 3 squirts of oil. Retest each cylinder & record.

Post dry & wet readings & post. We will comment.

Good luck!

 

Thank! I will try and do it some time late next week!

 

Okay!

So I did a compression check a few moments ago and here are the results. Oh and i did only a dry test. Does that make this test any less useful?

1. 160psi
2. 155psi
3. 155-160psi
4. 160-165psi

What do you think?

TIA

G

 

Looks pretty consistent. Was there a reason you were suspecting compression problems?

 

You have no problem with compression.

 

Thanks! There is oil coming mainly from the #1 spark plug hole. Just wanted to check for sanity purposes. Going to replace the valve cover gasket to to try and remedy that problem.

Thanks GMR!

Btw, do you guys know the exact torque spec for the spark plugs. Just got a torque wrench and next time i pull out the plugs (pretty soon to check for oil again), i want to use the correct torque spec. Thanks!

Is it 23 nM.....17 ftlbs?

 

15-22 ft.lbs./20-30 Nm

 

Thank you again

 

I am also going to perform this on a 2005 C230K. Do I need to disconnect any of the fuses (i.e. fuel)? Or should I perform test just as you described?

Thanks!!