DESCRIPTION & OPERATION
Note. 2.0L 4-cylinder diesel engines do not use an EGR system.
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.
2.4L Diesel EGR System Components. Scheme 59
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.
EGR VALVE
With engine off, apply vacuum with hand vacuum pump, then pull off EGR vacuum line while vacuum is applied. The valve should be heard to knock against the insert ring. If no knock is heard, valve is probably seized and should be replaced.
COOLANT TEMPERATURE SWITCH
Check switch continuity with ohmmeter. With coolant temperature above 122°F (50°C), the ohmmeter should indicate continuity.
IDLE SPEED SWITCH
Check continuity of switch with ohmmeter. Switch will open with .040" (1 mm) clearance between idle stop screw and control lever when injection pump control lever is operated. Continuity should be present at warm idle. No continuity should be present with throttle opened more than .040" (1 mm).
EGR CONTROL SOLENOID
Check air flow in switching valve at idle and at 1000-2800 RPM with coolant above 122°F (50°C). At this point there should be vacuum in connecting line between EGR solenoid and EGR valve. This can be felt by hand, or measured with vacuum gauge.
EGR MODULE
Check the switching points of the speed relay located inside the EGR module at 122°F (50°C). Switch is on at 940-1060 RPM and off at 2800 RPM. EGR valve should have vacuum when the switch is on. This can be felt by hand, or measured with vacuum gauge.
Scheme 60
Scheme 61
- Maximum speed and engine idle must be properly set. Place injection pump control lever so it rests on the idle stop. With engine off, connect a vacuum pump to connection "A" and a vacuum gauge to connection "B". (Scheme 60) (Scheme 60): Vacuum Regulator Check Connections
- Hold the injection pump control lever in the defined angle position using holding tool (T84P-7B200-A). (Scheme 61) In this position, control vacuum at "B" should be 9.4-9.8 in. Hg when reading at "A" reads a minimum of 16 in. Hg. for Federal models, or 11.10 in. Hg for California models. (Scheme 61): Defined Angle Tool in Position
- If vacuum reading is not correct, setting of connecting rod must be changed. Shortening the rod will increase vacuum, lengthening rod will decrease vacuum. Tighten lock nuts on rod and recheck adjustment.