The system injects a metered amount of exhaust gases into the incoming air/fuel mixture of the intake manifold to aid in the reduction of oxides of nitrogen in the exhaust by lowering the combustion temperatures.
This system is used on all carbureted engines except the 1974-75 Federal models with manual transmissions. The EGR system was included on fuel injected models at the beginning of the 1977 model year, except for the 1977 R17GTL model for the California market.
When the engine is cold and the coolant temperature is below 113 degrees F., the coolant thermal switch is closed, allowing the solenoid valve to be energized. If the throttle is at idle or in the wide open position, a control cam on the throttle shaft closes a micro switch and again allows the solenoid to become energized. When the solenoid is energized, manifold vacuum is denied to the EGR valve, but air pressure from the air pump (A.I.R. system) is allowed to act upon the valve to keep it closed. While the valve is closed, no exhaust gas recirculation is allowed.
As the engine warms up, the thermal switch opens and the solenoid is de-energized. This allows the manifold vacuum to pass to the EGR valve and the air pressure from the air pump to be closed off. This allows the exhaust gases to recirculate when the throttle is between idle and wide open, since the throttle shaft reacts on the micro switch in those two positions, allowing the EGR valve to open.
The EGR system consists of the following components:
Vacuum, pressure lines and hoses
Coolant temperature switch
EGR maintenance switch and reminder light
MAINTENANCE REMINDER LIGHT
The EGR maintenance warning light comes on at 25,000 mile intervals, indicating EGR system maintenance is required. The EGR system should be disassembled, the pipes and valves cleaned, along with the inlet at the intake manifold. The hoses and lines must be inspected for breakage, air leaks and deterioration. The electrical system should be checked for proper operation of the solenoid, micro switch and coolant temperature switch. The maintenance indicator light must be reset to begin its new mileage cycle.Resetting
The maintenance reminder indicator light control is located on the speedometer cable, mounted on the left-hand side of the shock absorber housing and is sealed by two lead seals with wires.
- Cut the sealing wires and remove the cover by releasing the clips.
- Turn the exposed knob 1 / 4 of a turn in the direction of the etched arrow, towards the mark "0", etched on the control base.
- This resetting the knob recycles the control and turns the EGR reminder light off.
- Install the control cover and reseal with new lead seals and wires.
TESTING & ADJUSTING
- With the engine at idle speed, current should be present at the solenoid terminal, causing the EGR valve not to operate.
- By placing a 0.156 inch feeler gauge (0.125 inch for automatic transmission models) between the idle speed adjusting screw and its stop. The micro switch contacts should open and current cease at the solenoid terminal, allowing the EGR valve to operate.
- Adjust the micro switch by using the adjusting slots in its bracket, if required.
- To check the EGR valve for proper operation while the engine is at idle, press the micro switch contacts with finger pressure to open the contacts. The engine should operate erratically or even stall, due to exhaust gas entering the intake manifold through the operating EGR valve. By releasing the micro switch contacts, the EGR valve should close and the engine return to normal idle.
REMOVAL & INSTALLATION
- Allow ample time for the engine to cool. The EGR valve has exhaust gases passing through it and can become quite hot.
- Disconnect the label the vacuum line connected to the EGR valve.
- Loosen and remove the EGR valve retaining bolts or nuts. Some models may also have a connector pipe which is screwed onto the EGR valve. Loosen the connector pipe retaining nut and position the pipe out of the way.
- Pull the EGR valve off of the engine.
- Remove all traces of the old EGR gasket.
- Installation is the reverse of removal. Always use a new gasket when installing the EGR valve.