EGR System Ford Cab & Chassis Ranger

DESCRIPTION

Exhaust Gas Recirculation (EGR) system is used to reduce NOx emissions. This is accomplished by recycling exhaust gases back into the intake manifold, resulting in cooler combustion temperatures and controlled NOx emissions.

EGR system used by Ford consists of an EGR valve, vacuum amplifier, vacuum reservoir, ported vacuum switch (PVS) and connecting lines and hoses.

Cutaway View of EGR Valve Without Backpressure Transducer When testing, apply 8 in. Hg to EGR Valve and hold it for at least 30 seconds. Scheme 55

OPERATION

EGR system is controlled by EGR valve. When valve is open, exhaust gas enters manifold passages. When closed, no exhaust gas is allowed to enter intake manifold. Vacuum signals control opening and closing of EGR valve.

Light Duty emissions EGR systems use backpressure transducer to aid in controlling exhaust gas recirculation. This unit senses exhaust gas back pressure and modulates vacuum signal to EGR valve in response to amount of back pressure. Backpressure is used to provide information on engine operation modes. Backpressure transducer is integral with EGR valve.

ELECTRONIC SONIC EGR VALVE

This valve operates like a ported valve, except tapered pintle is used for more exact flow control. Sensor mounted on top of this valve sends out electrical signals that tells Electronic Control Assembly (ECA) how far EGR valve is open.

Electronic EGR Valve System System used with EEC equipped vehicles. Scheme 56

ECA then signals EGR control solenoids to maintain or alter EGR flow as required. Source vacuum is from manifold and is bled off or applied to diaphragm by ECA. A cooler is sometimes used to reduce exhaust gas temperature, reduce detonation and allow better exhaust gas flow. This valve operates only at part throttle mode. It is closed in all other modes.

EGR VALVE WITHOUT BACKPRESSURE TRANSDUCER

1. Check that all vacuum lines are properly routed, all connections are secure, and that vacuum hoses are not cracked, crimped or broken. When engine is cold there should be no vacuum to operate the valve. If there is vacuum, check PVS function. Replace if necessary. There should be no vacuum to valve at warm curb idle.
2. Vacuum should be available at or above part throttle with engine at operating temperature. If vacuum is not available, check PVS function and replace as necessary.
3. With engine at idle, apply 8 in. Hg vacuum to EGR valve. Valve stem should move to open valve and produce a rough idle. If valve stem moves but idle does not change, remove valve and clean inlet and outlet ports with wire brush.
4. With engine at idle, trap 4 in. Hg vacuum in EGR valve and hold. Vacuum should not drop more than 1 in. Hg in 30 seconds.
5. If vacuum drops, replace valve. To test valve seat, insert blocking gasket (no flow holes) between valve and mounting base, then retighten valve. If idle improves, replace valve and remove blocking gasket. If idle does not improve, problem is not in EGR system.

Integral Backpressure Transducer & EGR Valve Valve cannot be opened by vacuum, until bleed hole is closed by exhaust backpressure. Scheme 57

Signal Response Test

1. Check that all vacuum lines are properly routed, all connections are secure and that vacuum hoses are not cracked, crimped or broken. Disconnect vacuum line to EGR valve and plug line. Connect vacuum pump to EGR valve. Apply vacuum to valve. Vacuum (6 in. Hg) should bleed off and valve should not operate. If vacuum holds and valve stays open, replace valve.
2. When engine is cold there should be no vacuum to operate valve. If there is vacuum, check PVS function and replace if necessary. There should be no vacuum to valve at idle under any conditions.
3. Vacuum should be available at or above part throttle with engine at operating temperature. If vacuum is not available, check PVS function. Replace as necessary.

Valve Function Test

1. Clamp drive socket wrench into tailpipe. Socket outside diameter should be about 1/16" less than tailpipe inside diameter. Socket drive hole should be covered and socket should be inserted into tailpipe with open end facing out to ensure proper backpressure.
2. Do not block tailpipe fully or run engine faster than idle for prolonged periods of time. Be sure to remove socket from tailpipe at end of test.
3. Idle engine and apply vacuum to EGR valve gradually. EGR valve diaphragm should move smoothly and rough idle should occur. Trap 6 in. Hg vacuum in EGR valve and hold. Vacuum should drop more than 1 in. Hg in 30 seconds.
4. If vacuum does not drop or diaphragm does not move, replace valve. If diaphragm moves but idle does not change, remove valve and clean inlet and outlet ports with wire brush.
5. If valve is suspected of sticking, remove valve from engine. Cycle valve by pressing carefully with fingers against lower transducer plate. If valve sticks open when fingers are released, replace valve. If valve does not stick and correct vacuum signal is present at valve, check valve for carbon deposits and clean as necessary.
6. If engine has less than 6000 miles on it, is idling rough, and valve is suspected of being open, remove valve and check valve for foreign material. Tap base of valve on table while holding valve open with fingers. If foreign material falls from valve, make sure valve closes and reassemble valve to engine.
7. Reconnect vacuum line and check for rough idle. If rough idle continues and valve is still sticking, replace valve. If valve is not sticking, rough idle problem is not in EGR system.

1. Connect vacuum gauge to valve. Apply 6 in. Hg vacuum to valve and trap. Vacuum should not drop more than 1 in. Hg in 30 seconds. If so, replace valve "O" ring or EVP sensor.
2. As sonic valve is part of EEC system, check all circuitry as described in EEC article. See COMPUTERIZED ENGINE CONTROL section. Mechanical function can be checked as follows: Check vacuum lines for correct routing.
3. Disconnect vacuum hose at valve and connect vacuum gauge to hose. Accelerate engine to 2000-2500 RPM and release throttle. Repeat 8-10 times and check for consistent response.
4. If vacuum rises above zero, when engine is cold, diaphragm is leaking and valve should be replaced. With engine warm, vacuum should not rise above 15 in. Hg and should return to zero when throttle is released.
5. If vacuum does not go to 15 in. Hg, check vacuum source and service. If vacuum does not return to zero or is inconsistent, solenoid is worn and should be replaced.

CARBURETOR EGR PORT

1. Attach vacuum gauge directly to EGR carburetor port, using hose. Start engine, quickly open throttle to halfway position and close.
2. Observe vacuum gauge for quick rise and fall as throttle is opened and closed. If definite vacuum is evident, port is okay. If not, port is clogged and must be cleaned.

PVS with 2 Connections

1. Detach both vacuum hoses from PVS, and connect vacuum gauge to top port on PVS. Connect other PVS nipple to manifold vacuum or external vacuum supply of at least 10 in. Hg. (Scheme 58)
2. Start engine and warm until engine operating temperature is reached. If no vacuum reading is noted, PVS should be replaced. If vacuum is present, PVS is okay.

PVS with 3 Connections

1. Disconnect EGR vacuum hose from PVS and connect manifold vacuum or external vacuum source to lowest port on PVS. (Scheme 59)
2. Detach distributor supply hose from center port, and attach vacuum gauge to center port.
3. Start engine and warm up until engine operating temperature is reached. If no vacuum is present, replace PVS. If present, PVS is okay.

Cutaway View of 2-Port PVS PVS will open when engine reaches operating temperature. Scheme 58

Scheme 59

1. Disconnect vacuum hoses at PVS valve. Connect vacuum gauge to top port of PVS. Connect external vacuum source to 2nd port. (Scheme 60)
2. Start engine and warm up until engine operating temperature is reached. If no vacuum, this portion of PVS is damaged and valve should be replaced. If vacuum is present, proceed to next step. (Scheme 59): Cutaway View of 3-Port PVS Warm engine should indicate vacuum at center PVS port.
3. Connect gauge to 3rd port and vacuum supply to bottom port. If vacuum is noted, PVS is okay. If no vacuum, replace PVS.

Cutaway View of 4-Port PVS Connect vacuum gauge to 1st & 3rd port to check PVS. Scheme 60

VENTURI VACUUM AMPLIFIER

Note. Amplifiers have built-in calibrations, and no external adjustments are required. If amplifier bias test reveals malfunction, replace amplifier. Always check venturi vacuum amplifier last, after checking all other basic EGR components.

1. With engine at normal operating temperature, curb idle set and adequate manifold vacuum supplied to system, connect vacuum gauge to hose at amplifier port "O". Gauge may read as much as 2 in. Hg at idle.
2. Disconnect venturi hose (amplifier port "V") at carburetor and increase engine speed to 2000-3000 RPM. Vacuum should not change.
3. While maintaining high engine speed, connect venturi hose. Vacuum should increase to 4 in. Hg. Return to idle. Gauge should return to initial reading. If amplifier does not perform as specified, replace amplifier.

Testing Ford Venturi Vacuum Amplifier Amplifiers do not require external adjustments. Scheme 61

VACUUM AMPLIFIER RESERVOIR

When charged with 15-20 in. Hg vacuum, vacuum loss should not exceed .5 in. Hg in 60 seconds. If it does, replace reservoir.

REMINDER LIGHT RESET PROCEDURE

1. Turn ignition off. Insert Phillips screwdriver into hole in timer unit. While pressing screwdriver in, turn ignition to "RUN" position.
2. Light should be on. Hold screwdriver in for 5 seconds. Remove screwdriver. Light should go out in 2-10 seconds. If not repeat steps 1) and 2).
3. Turn ignition off. Turn ignition to "RUN" position. Light should come on for 2-10 seconds. This verifies proper reset of light module.