Feedback Control System
Feedback Control System TestHOT ENGINE
1. Disconnect #14 hose from the power valve and install a plug in the hose.
2. Start the engine and warm it up to normal operating temperature (the cooling fan comes on). Check that the frequency solenoid valves A and B are operating when the engine speed is raised to approx. 2,500 rpm.
The frequency solenoid valves should go on and off continuously (a continuous clicking noise should be heard).
NOTE:
- It may be easier to determine if the valves are working by placing your hand on each valve individually.
- If both solenoid valves operate properly, go on to step 3.
- If either solenoid valve A or B does not operate properly, replace it and retest.
3. Connect #14 hose to the power valve. With the air conditioner off, if so equipped, check that frequency solenoid valves A and B are not operating while idling the engine.
The solenoid valves should not operate.
Air Bleed Valve B
1. Disconnect #33 hose from the vacuum hose manifold and connect a vacuum pump/gauge to the
2. Apply vacuum to the hose.
It should hold vacuum.
- If it does not hold vacuum, replace the air bleed valve B and retest.
3. Warm the air bleed valve B with a dryer and apply vacuum to the hose.
It should not hold vacuum.
NOTE: Air bleed valve B opens at 65°C (149°F)
- If it holds vacuum, replace the air bleed valve B and retest.
Air Control Valve A
1. Disconnect #16 hose from air control valve A and connect a vacuum pump/gauge to the hose.
2. Pinch upper large hose.
3. Disconnect lower hose from air control valve A and connect a vacuum pump/gauge to the hose. Apply vacuum to lower hose.
4. Release upper large hose.
5. Now apply vacuum with the vacuum pump attached to #16 hose.
The lower hose should not hold vacuum at all (unrestricted leak).
If the valve fails either check, replace it.
Air Control Valve B
1. Disconnect #32 hose from the vacuum hose manifold and connect a vacuum pump/gauge to the hose.
2. Disconnect the lower hose from air control valve B, and warm up to normal temperature (cooling fan comes on).
Check for vacuum at idle.
There should be no vacuum.
3. Now at idle apply vacuum with the vacuum pump attached to #32 hose.
The engine should stall and the valve should hold vacuum.
If the valve fails either check, replace valve or #32 hose.
4. Install three-fitting and vacuum pump/gauge between #32 hose and install pipe.
- There should be no vacuum at idle.
- There should be approx. 2-5" of vacuum at 2,500 rpm.
Constant Vacuum Generator
1. Disconnect #33 hose from frequency solenoid valve B and connect a vacuum gauge to the hose.
2. Start the engine, allow it to idle, then check for vacuum.
Vacuum should stabilize at:
49 ST and HI ALT:
180 - 280 mmHg (7.1 - 11.0 in. Hg)
CAL:
150 - 250 mmHg (5.9 - 9.8 in. Hg)
- If the vacuum stabilizes within the specified vacuum, the constant vacuum generator is OK. Reconnect the hose to frequency solenoid valve B.
- If the vacuum does not stabilize, or stabilizes outside the specified vacuum range, replace the constant vacuum generator.