DESCRIPTION
The Exhaust Gas Recirculation (EGR) system recirculates exhaust gases into the combustion chamber to reduce combustion temperatures. The reduction in temperature acts to reduce Oxides of Nitrogen (NOx) emissions.
OPERATION
When the EGR valve is held open, some of the exhaust gas is led from the exhaust manifold to the EGR tube. The exhaust gas is then regulated by the EGR valve, and introduced into the intake manifold. The signal from the ECCS control unit is sent to the EGR control solenoid valve, which cuts the vacuum line for the EGR control valve when engine is starting, throttle valve switch is on, engine coolant temperature is low or high, engine speed is low or high, or during deceleration.
EGR VALVE
- Remove EGR valve from engine and inspect it for damage. Apply vacuum to EGR valve and watch diaphragm movement.
- Diaphragm should move to fully open position and should remain in this position for at least 30 seconds after vacuum is shut off.
- Before reinstalling EGR valve, clean mating surface with a wire brush and compressed air. Remove foreign material from around valve and port.
Scheme 11
BACKPRESSURE TRANSDUCER (BPT) VALVE
Disconnect 2 vacuum hoses on BPT valve. Plug one of 2 ports. Apply .145 in. Hg vacuum to BPT valve and apply suction on other port to check for leakage. If leak is noticed, replace valve.
Scheme 12
The EGR system on all models is controlled by the ECCS control unit. See ELECTRONIC CONCENTRATED ENGINE CONTROL SYSTEM article for testing.
