Need some help!

My ch 600 1994 is running in 5 cylinders and pumpimg black smoke.litle power. I replaced the inyector number 6 after identifying that one was running bad,No improvements.So I changed the delivery valve of injector number 6.

still no improvement.

I tried using the new inyector number 6 on number 4 and is ok but back to 6 it does not work.

Calling around they tell me ,why dont you check the compresion ,may is the the valve on piston number 6.Others think may be is the fuel inyection pump.but it is running ! so others say it cant be.

any suggestions?

I cant even find where to rent the tool to get a compression test .Im in 95133.

Thanks in advance to all for your time in answering.