Chrysler Full-Size Vans 1989-1998 Repair Guide

Exhaust Gas Recirculation System

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OPERATION



See Figures 1, 2, 3 and 4

The Exhaust Gas Recirculation (EGR) system reduces oxides of nitrogen (NOx) in engine exhaust and helps prevent spark knock. This is accomplished by allowing a predetermined amount of hot exhaust gas to recirculate and dilute the incoming fuel/air mixture. This dilution reduces peak flame temperature during combustion.

The EGR system is a backpressure type. A backpressure transducer measures the amount of exhaust backpressure on the exhaust side of the EGR valve and varies the strength of the vacuum signal applied to the EGR valve. The transducer uses this backpressure signal to provide the correct amount of Exhaust Gas Recirculation under all conditions. The 3.9L, 5.2L and 5.9L engines use manifold vacuum controlled by a electronically controlled vacuum solenoid.

EGR System On-Board Diagnostics (California Vehicles Only): All California vehicles with EGR systems have an On-Board Diagnostic System for the EGR system. The Diagnostic System uses a solenoid in the vacuum signal line to the EGR valve. The system is monitored by the ECM during certain driving conditions, and if a fault is detected, turns on the Check Engine Light and stores a DTC. If a EGR fault is retrieved from the ECM, use the testing procedures provided later to diagnose the system.

The Diagnostic System Check is activated only during selected engine/driving conditions to avoid mis-diagnosis, and checks the entire EGR system for failures. The engine controller monitors EGR system performance and registers a fault code if the system has failed or degraded, and the dash-mounted check engine light is turned on indicating immediate service is required.

If a malfunction is indicated by a check engine light and a fault code for EGR system, proper operation of the EGR system should be checked. If the EGR system is found to be functioning correctly, the on-board diagnostics system should then be checked.



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Fig. Fig. 1: EGR valve and transducer-1989-91 vehicles



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Fig. Fig. 2: Detailed view of an EGR valve and transducer assembly-1989-91 vehicles



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Fig. Fig. 3: EGR valve and control assembly-1992-98 vehicles



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Fig. Fig. 4: Detailed view of an EGR valve and control assembly-1992-98 vehicles

COMPONENT TESTING



EGR Control System Test
  1. Remove the engine cover.
  2.  
  3. Start and warm up the engine.
  4.  
  5. Allow it to idle with the parking brake firmly set.
  6.  
  7. Allow the engine to idle in Neutral with the throttle closed, then quickly accelerate the engine speed to approximately 2000 rpm.
  8.  
  9. Watch the EGR movement indicator (groove) on the valve stem. If the valve stem moves, the EGR system is operating correctly.
  10.  
  11. If no movement is noted, continue diagnosis with other EGR tests.
  12.  

EGR Gas Flow Test

See Figures 5 and 6

  1. Remove the engine cover.
  2.  
  3. Connect a tachometer to the engine.
  4.  
  5. Remove the vacuum hose or rubber elbow from the EGR valve and connect a hand vacuum pump to the EGR valve vacuum nipple.
  6.  
  7. Start the engine and slowly apply vacuum to the EGR valve diaphragm.
  8.  
  9. The engine speed should drop as vacuum reaches 3-5 in. Hg and continue to drop as more vacuum is applied. The engine may even stall. This means EGR gas is flowing through the system.
  10.  
  11. If the engine speed doesn't drop, check for a failed EGR valve or plugged EGR passage. Remove the EGR valve and inspect/repair as necessary.
  12.  



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Fig. Fig. 5: Disconnect the EGR vacuum line



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Fig. Fig. 6: Using a hand held vacuum pump to verify EGR diaphragm operation

EGR Valve Leakage Test
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the engine cover.
  4.  
  5. Disconnect the hose from the fitting from the top of the EGR valve.
  6.  
  7. Connect a hand-held vacuum pump to the fitting and apply 15 inches of vacuum to the valve. Observe the gauge reading on the pump; if vacuum falls off, the diaphragm in the EGR valve has ruptured, and the EGR valve must be replaced. If vacuum remains, proceed to next step.
  8.  
  9. Remove the hose from the bottom of the EGR valve. Using compressed air (if available) and an air nozzle with rubber tip, apply 50 psi of regulated air pressure to the fitting.
  10.  
  11. Using your hand, open the throttle all the way, and listen inside the throttle body, if air is escaping, the poppet valve in the base of the EGR valve is leaking. Replace the EGR valve.
  12.  

EGR Vacuum Transducer Valve Control

See Figures 7, 8, 9 and 10

  1. Remove the engine cover.
  2.  
  3. Remove the hose on the bottom of the EGR valve control.
  4.  
  5. Connect a hand-held vacuum pump to the fitting and apply 10 inches of vacuum. If the vacuum falls off, the valve control diaphragm is leaking. Replace the EGR valve control and retest. If OK, connect hose proceed to next step.
  6.  
  7. Remove the hose at the EGR valve control inlet.
  8.  
  9. Connect a vacuum gauge to this hose.
  10.  
  11. Start the engine and bring it to operating temperature.
  12.  
  13. Hold the engine speed at approximately 1500 RPM. Check for steady manifold vacuum at this hose.
  14.  

To figure out what the vacuum should be, remove a vacuum hose directly from the intake manifold and measure the vacuum at 1500 RPM.

  1. If manifold vacuum is not present, check for vacuum leaks on line or lack of manifold vacuum. Repair as necessary and retest. If manifold vacuum was OK, shut off engine, connect hose, and proceed to next step.
  2.  
  3. Disconnect the hose at the vacuum valve control outlet fitting.
  4.  
  5. Connect a vacuum gauge to this fitting.
  6.  
  7. Disconnect the electrical connector on the valve control. This will simulate an open circuit at the valve control.
  8.  
  9. Start the engine and bring it to operating temperature.
  10.  
  11. Hold the engine speed at approximately 2000 RPM while checking for vacuum flow through the valve control.
  12.  
  13. The gauge reading will be low, at idle speed the gauge reading should be erratic. This is normal.
  14.  
  15. To allow full manifold vacuum to flow through the valve control, exhaust backpressure must be present. It must be high enough to hold the bleed valve in the transducer portion of the valve control closed. Have a helper momentarily (a few seconds) block the exhaust with a rag or other suitable device.
  16.  


CAUTION
Make sure to have the helper wear heavy gloves to reduce the risk of burns from the exhaust gas or exhaust pipes.

  1. As temporary backpressure is built, full manifold vacuum should be observed.
  2.  
  3. If full vacuum was present at the inlet fitting, but is not present at the outlet fitting, replace the valve control.
  4.  
  5. Install the engine cover.
  6.  



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Fig. Fig. 7: Disconnect the EGR backpressure hose



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Fig. Fig. 8: Remove the vacuum feed line to the EGR control valve



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Fig. Fig. 9: Check for vacuum supply to the control valve



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Fig. Fig. 10: Detach the electrical connector from the EGR control valve

REMOVAL & INSTALLATION



EGR Valve

See Figures 11, 12, 13, 14 and 15

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the engine cover.
  4.  
  5. Disconnect the vacuum line to the EGR valve. Inspect for damage.
  6.  
  7. Remove the two EGR valve mounting bolts from the intake manifold.
  8.  
  9. Remove the EGR valve from the intake manifold.
  10.  
  11. Clean the gasket surface and discard the old gasket. Check for any signs of leakage or cracked surfaces.
  12.  

To install:
  1. Assemble the EGR valve with a new gasket onto the intake manifold.
  2.  
  3. Install the EGR valve mounting bolts and tighten them to 200 inch lbs. (22 Nm).
  4.  
  5. Reconnect the vacuum line.
  6.  
  7. Connect the negative battery cable.
  8.  
  9. Start the engine and check for exhaust leaks.
  10.  
  11. Install the engine cover.
  12.  



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Fig. Fig. 11: Unfasten the EGR valve retaining bolts



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Fig. Fig. 12: Remove the EGR valve



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Fig. Fig. 13: Look inside the EGR passages of the intake manifold for blockage



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Fig. Fig. 14: Thoroughly clean the EGR mounting surface



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Fig. Fig. 15: Be sure to install a new gasket with the EGR valve

EGR Solenoid
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the engine cover.
  4.  
  5. Label and remove the vacuum hoses and electrical connectors from the solenoid(s).
  6.  
  7. Remove the fasteners and remove the solenoid pack.
  8.  
  9. Depress the tab on top of the solenoid to be replaced and slide the solenoid down out of the mounting bracket.
  10.  

To install:
  1. Place the new solenoid it position and slide in up into the bracket until the mounting tab is secure.
  2.  
  3. Mount the solenoid in position and secure it with the mounting fasteners.
  4.  
  5. Attach the vacuum lines and wiring connectors to the solenoid(s).
  6.  
  7. Connect the negative battery cable.
  8.  

 
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