mercedes 300sd 1982 HELP PLEASE

Check the compressions and report the readings here,

mark (mhpautos)

from front to back 1-310 2-300 3-0 4-300 5-315

I would be looking at a fuel delivery problem, have you had the injectors tested?

Mark (mhpautos)

No but the number 3 cylinder has no compression

OHH sorry i did miss read that, early morning here and i am still having a heart starter coffee.... well no comp is a problem, you will have to get a leak down test done, this is a air fitting fitted into the glow or injecter port and at TDC on that cyl low pressure air is added, you will hear it leaking out the exhaust or inlet if a valve or in the Rocker cover if a piston problem, i would also just re check the valve clearances on that cylinder as well.

mark (mhpautos)

I have checked th em again and again they were reall tight whene I got car couple weaks ago could it be a burnt vvavle

more that likely it will be a burnt valve, the leak down test will prove this, regardless with no compression the head will have to come off to investigate anyway.

mark (mhpautos)

Ok how can you tell a burnt valve by looking at it

Best way to check with the head off, is that it will be visible burnt with a section burnt away, if it looks ok, with both valves fully closed invert the head and pour a little kerro around the valve, if it drains away, leaking valve, but with 0 comp, i feel that you will see a bad valve quite easily.

Mark (mhpautos)

Removed head the piston has a hole bout the size of a dime in it thanks for your help I wont be fixing this one just part it out