Description & Operation
The exhaust gas recirculation (EGR) system used on Ford Motor Co. 2.4L 6-cylinder diesel engines differs from that used on gasoline engines. Most gas engines do not receive any EGR at idle, whereas the 2.4L diesel receives full EGR at idle. Most oxides of nitrogen (NOx) emissions are produced during lean conditions and for this engine maximum lean conditions occur at idle and off idle, instead of at cruise speeds as in a gasoline engine.
The EGR system consists of the following components: An EGR valve, EGR control solenoid, EGR module, coolant temperature switch, vacuum regulator, idle speed switch, position sensor, vacuum pump and vacuum reservoir and vacuum delay valves.
These components perform the following functions: The EGR valve, located in the exhaust manifold, controls exhaust gas recirculation from exhaust manifold to intake manifold. The EGR solenoid, located on the cowl, controls vacuum to EGR valve. The EGR module, located on the cowl, controls EGR at speeds above idle between 1000 and 2800 RPM. The coolant switch, located in the cylinder head, senses coolant temperatures and closes above 122°F (50°C). The vacuum regulator, located on top of the injection pump, controls the amount of EGR in relation to amount of fuel injected.
The idle speed switch, located on the injection pump, controls EGR at idle. The position sensor, located at lower left of engine block, counts engine revolutions. The vacuum pump, located on the cylinder head, supplies EGR controlling vacuum. The vacuum reservoir valve, located on top of the injection pump, prevents pulsations to the vacuum regulator. The vacuum delay valve improves driveability by modulating the start of EGR.
The operating range of the EGR system is limited to the following operating conditions by the EGR control solenoid: 1) At idle speed (750-800 RPM) when partial load enrichment is canceled. Partial load enrichment provides the engine with more fuel and extra advance when cold. This enrichment is canceled when coolant temperature is above 86°F (30°C). 2) At partial load between 1000 and 2800 RPM if the coolant temperature is above 122°F (50°C). There should never be any EGR operation when engine speeds are above 2800 RPM with the engine under full load, or when the engine is cold.