Non-Trouble Code Procedures

An engine driven vacuum pump, a one-way check valve and vacuum lines are used to supply vacuum to the speed control servo. A vacuum reservoir is not used.
1. Disconnect vacuum hose at speed control servo and install a vacuum gauge into the disconnected hose.
2. Start engine and observe gauge at idle.
3. If vacuum pump output is OK, determine other source of leak. Check all vacuum lines to: speed control servo, engine vacuum pump and heating/air conditioning system for leaks.
4. Verify operation of one-way check valve and check it for leaks.
a. Locate one-way check valve. The valve is located in vacuum line between speed control servo and engine vacuum pump. Disconnect vacuum hoses (lines) at each end of valve.
b. Connect a hand-operated vacuum pump to reservoir end of check valve. Apply vacuum. Vacuum should not bleed off. If vacuum is being lost, replace one-way check valve.
c. Connect a hand-operated vacuum pump to vacuum source end of check valve. Apply vacuum. Vacuum should flow through valve. If vacuum is not flowing, replace one-way check valve. Seal the fitting at opposite end of valve with a finger and apply vacuum. If vacuum will not hold, diaphragm within check valve has ruptured. Replace valve.