Positive Crankcase Ventilation: Testing and Inspection

Fig. 30 Checking PCV valve vacuum:

Fig. 31 Checking vacuum at crankcase inlet filter (Typical). except 4 cylinder & V6-181 engines:

1. With engine running at idle, proceed as follows:
a. Remove PCV valve from rocker cover. If valve is not plugged, a hissing noise will be heard as air passes through the valve, and a strong vacuum will be felt at the valve inlet, Fig. 30.
b. Reinstall PCV valve and remove crankcase inlet air filter. Loosely hold a piece of stiff paper over opening in rocker cover, Fig. 31. When crankcase pressure decreases after approximately one minute, the paper should be drawn firmly against the opening.
2. Stop engine and remove PCV valve. When valve is shaken, a clicking noise should be heard, indicating freedom of the valve mechanism.
3. If system passes tests in steps 1 and 2, no further service is required. If not, replace PCV valve and recheck system. Never attempt to clean an old PCV valve.
4. If, after a new PCV valve has been installed, the paper is not drawn against crankcase inlet air cleaner opening in rocker cover, the ventilator hose and passages in lower portion of carburetor must be cleaned. To clean hose and passages, proceed as follows:
a. Clean carburetor hose with a suitable solvent and dry with compressed air. Do not allow hoses to remain in solvent for more than 1/2 hour.
b. Remove carburetor and hand turn a 1/4 inch or smaller drill through the passages to dislodge any solid particles, then blow clean. It is not necessary to disassemble the carburetor for this procedure.
5. Clean the crankcase inlet air cleaner with a suitable solvent, then fill the filter with SAE 30 engine oil.
6. Clean or replace the carburetor air cleaner.