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 check that the frequency solenoid valves A and B are operating while running the engine at 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.
- If both solenoid valves do not operate properly, go to output troubleshooting.
3. Connect # 14 hose to the9ower 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.
- If the solenoid valves operate, go to input troubleshooting.
Feedback Control Solenoid Valve
1. Disconnect # 32 hose from feedback control solenoid valve and plug the end of the hose.
2. Connect a vacuum pump/gauge as shown.
3. Start the engine and apply vacuum to the valve.
It should not hold vacuum.
- If it does not hold vacuum, go on to step 4.
- If it holds vacuum, go to output troubleshooting.
4. Raise speed to 2,500 rpm and apply vacuum to the valve.
It should hold vacuum.
- If it does not hold vacuum, go to output troubleshooting.
Air Bleed Valve B
1. Disconnect # 39 hose from the vacuum hose manifold and connect a vacuum pump to the hose.
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 to the hose.
2. Disconnect the lower hose from air control valve A, connect a vacuum pump to the hose.
Apply vacuum to the valve. It should have a restricted leak.
3. 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 air control valve B and connect a vacuum pump to the hose.
2. Disconnect the lower hose from air control valve B, connect a vacuum pump to the hose. Apply vacuum to the valve.
It should hold vacuum.
3. Now apply vacuum with the vacuum pump attached to # 32 hose.
Vacuum should now release at the lower hose. If the valve fails either check, replace it.
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 - 28O mm Hg 7.1 - 11.0 in. Hg
CAL
150 - 250 mm Hg 5.9 - 9.8 in. Hg
- If the vacuum stabilizes within the specified vacuum, the constant vacuum generator is OK. Re connect the hose to frequency solenoid valve B
- If the vacuum does not stabilize, or stabilize' outside the specified vacuum range, replace the constant vacuum generator.