Defective Vacuum Control Unit

On 5-cylinder 300 series engine, engine oil can enter vacuum system through a defective diaphragm in the vacuum control unit. Sometimes vacuum pump has been mistakenly blamed. If complaints are received that engine does not shut off or shuts off with difficulty, check vacuum control unit first as follows:

1. Remove brown and blue line from vacuum control unit. Check for traces of oil. If present, replace unit and oil-filled vacuum lines. Also repair vacuum pump and replace brake booster if oil is found at connecting fitting for vacuum line.
2. If no traces of oil are found at control unit or in vacuum lines, start engine and run at idle. Pull off brown vacuum line from "T" fitting between vacuum pump and brake booster. See Figure. Check for vacuum. If none present, remove and check "T" fitting and clean with compressed air.
3. If vacuum is present, connect vacuum control unit directly to "T" fitting (by-pass the valve). Pump is now free to act directly upon diaphragm of control unit. If engine does not shut off immediately, replace control unit.
   NOTE: When installing new unit, be sure control linkage in pump governor is properly engaged and is not holding main rack in full-load position.
4. If engine shuts off immediately, vacuum control unit is not to blame. Problem could then be jammed vacuum valve in steering lock.
5. Be sure all vacuum lines are connected as shown in Fig. 10  . Start engine, check vacuum control unit, valve in steering lock and injection pump for leaks.