Electronically Controlled System
EXCEPT CABALLERO, EL CAMINO & 1985-87 MODELS W/ HEAVY DUTY EMISSIONS
DESCRIPTION
The Air Management System provides filtered air, under certain conditions, to the exhaust manifold to continue the combustion process after the exhaust gases have left the combustion chamber. This continued combustion aids in reducing HC and CO levels in the exhaust and also helps in maintaining ideal catalytic converter operating temperatures.
Electric Air Control (EAC) Valve:
Fig. 12 Electric Air Control Valve With Relief Tube (ECT):
SYSTEM OPERATION
This system consist of a belt driven air pump, internal drilled passages in the cylinder head or manifolds, piping and hoses, electric air control valve and check valves. The vane type air pump supplies air through a centrifugal filter fan to the electric air control (EAC) valve, Fig. 11. On 1987 V6-262 and V8 engines, an electric air control valve with relief tube (ECT) is used, Fig. 12. The electric air control valve directs air to either the exhaust manifold ports or the air cleaner, which also acts as silencer.
On all engines except 1987 Federal V6-173 engines, at cold engine coolant temperatures or at wide open throttle conditions, the Electronic Control Module (ECM) will energize the electric air control valve solenoid, directing the air to the exhaust manifold ports. At higher engine coolant temperatures, the electric air control valve solenoid is de-energized, directing air to the air cleaner. Also at higher engine speeds, air is directed to the air cleaner through the pressure relief valve even though the solenoid may be energized. During engine deceleration, a rise in the manifold vacuum signal to the electric air control valve, will cause the valve to direct the air to the air cleaner. When the engine is operating in the closed loop mode, air flow should be to the air cleaner, with no air flow to the exhaust ports.
On Federal 1987 V6-173 engines, the Electronic Control Module (ECM) will energize the electric air control valve whenever the engine is started, directing air flow to the exhaust ports. Air flow will only be directed to the air cleaner during deceleration.
On all engines, the check valve(s), which is located on the air injection pipe, will prevent reverse exhaust gas flow into the air pump in the event of a air pump drive belt failure or exhaust system afterfire. When the engine is operating under a rich condition or if the service soon lamp is illuminated, the electric air control valve solenoid will be de-energized.
DIAGNOSIS & TESTING
Refer to "Except Electronically Controlled System, Diagnosis and Testing" for components not covered in this section.
Fig. 13 Electric Air Control (EAC) diagnosis chart. Except 1983 S/T10-15 V6-173 w/ man. trans., S/T10-15 cab-chassis w/auto. trans., 1983-84 G Series 6-250 w/man. trans. & 1987 Federal V6-173:
Fig. 14 Electric Air Control (EAC) Valve schematic. Except 1983 S/T10-15 V6-173 w/ man. trans., S/T10-15 cab-chassis w/auto. trans., 1983-84 G Series 6-250 w/man. trans. & 1987 Federal V6-173:
Fig. 15 Electric Air Control (Diverter) Valve diagnosis chart. 1983 S/T10-15 V6-173 w/man. trans., S/T10-15 cab-chassis w/auto. trans. & 1983-84 G Series 6-250 w/man. trans.:
Fig. 16 Electric Air Control (Diverter) Valve schematic. 1983 S/T10-15 V6-173 w/man. trans., S/T10-15 cab-chassis w/auto. trans. & 1984-84 G Series 6-250 w/man. trans:
Electric Air Control Valve
On all engines except 1987 Federal V6-173, refer to Figs. 13 through 16, when diagnosing electric air control valve problems.
On 1987 Federal V6-173 engines, if system is not functioning properly, check for manifold vacuum signal of 10 inches Hg. of vacuum at valve. Also check electrical circuit from valve solenoid to ECM.
SERVICE
Refer to "Except Electronically Controlled System, Service" for components not covered in this section.
Electric Air Control Valve, Replace
1. Disconnect battery ground cable, then disconnect electrical connector from valve solenoid.
2. Disconnect vacuum lines and air inlet and outlet hoses from valve.
3. Remove electric air control valve.
4. Reverse procedure to install. After completing installation, check system for proper operation.
1985-87 MODELS W/HEAVY DUTY EMISSIONS
DESCRIPTION
The air injection system used on vehicles with heavy duty emissions utilize increased air flow over other models to reduce CO and HC emission levels. The AIR system provides additional oxygen to continue combustion after the exhaust gases leave the combustion chamber. This system diverts air from the exhaust manifold at increased engine speed or when a malfunction is detected in the system.
The AIR system used on vehicles equipped with a 6-292 engine consists of an air pump, air filter, air control valve, check valve, silencer, control module and injection nozzles.
The AIR system used on vehicles equipped with V8-350 or V8-454 engines consists of two air pumps, air filter, two air control valves, a control module and injection nozzles.
Electric Air Control (EAC) Valve:
SYSTEM COMPONENTS
Air Control Valve
This valve is a high flow electric air control valve that is equipped with an electric solenoid to combine electronic control with normal diverter valve function, Fig. 11.
With ignition ``On'', the solenoid is energized through the control module and the air control valve operates like a diverter valve directing air to the exhaust manifold. During engine deceleration, when there is a rise in manifold vacuum, air is directed to the air cleaner or silencer even though the solenoid is energized. The solenoid is de-energized when there is a malfunction of the electrical circuit or high engine RPM over a prolonged period.
Deceleration Valve (DEC-V) Operation:
Deceleration Valve
The deceleration valve is used with the AIR system to help prevent backfiring during high vacuum conditions, Fig. 17. Vacuum draws the mixture valve diaphragm down and opens the valve allowing air from the air cleaner to flow into the intake manifold.
Air Pumps(s)
Refer to ``Air Pump, Except Electronically Controlled System''.
DIAGNOSIS & TESTING
Refer to ``Except Electronically Controlled System Diagnosis & Testing'' for service procedures not covered in this section.
Fig. 18 Control module test. 1985-87 models w/ heavy duty emissions:
Control Module Test
1. Turn ignition to ``On'' position.
2. Disconnect each solenoid connector, then using a suitable test light, check for voltage between solenoid connector pink/black wire and ground , Fig. 18.
3. If voltage does not exist, check for an open in circuit 39. If voltage does exist proceed to step 4.
4. Check solenoid terminals for voltage. If voltage exists, check solenoid resistance. If resistance is less than 20 ohms, replace solenoid and valve. If voltage does not exists, check for open in circuit 436 or for a faulty control module.
5. Connect solenoid connectors, then disconnect connector at control module. Check for voltage between terminals ``A'' and ``B'', Fig. 18. If voltage exists, replace module. If voltage does not exists, check for an open circuit to the control module.
SYSTEM SERVICE
Refer to ``Except Electronically Controlled System System Service'' for service procedures not covered in this section.
Filter, Replace
1. Loosen clamp securing filter, then remove filter from clamp.
2. Disconnect hose from air intake and pump.
3. Reverse procedure to install.
Silencer, Replace
1. Disconnect hose from silencer.
2. Remove bolt securing silencer, then silencer.
3. Reverse procedure to install.