Volvo Coupes/Sedans/Wagons 1970-1989 Repair Guide

Exhaust Gas Recirculation (EGR) System

Print

OPERATION



See Figures 1, 2 and 3

All 1980 and later U.S. models are not equipped with EGR systems.

In order to control emissions of NOx, all 1973-74 140 series, 164E and 1800ES models with automatic transmissions, as well as 1975 164, 240 and 260 series, were equipped with an exhaust gas recirculation system.



Click image to see an enlarged view

Fig. Fig. 1: Cutaway view of the vacuum amplifier-B20 engines



Click image to see an enlarged view

Fig. Fig. 2: EGR system for B27F and B28F engines-upper: without vacuum amplifier; lower: with vacuum amplifier



Click image to see an enlarged view

Fig. Fig. 3: EGR system for B21 and B23 engines-upper: without vacuum amplifier; lower: with vacuum amplifier

The system consists of a metering valve (EGR valve), a pipe running from the exhaust manifold to the EGR valve, another pipe running from the valve to the intake manifold, and a vacuum hose running from the EGR valve's diaphragm to the intake manifold in front of the throttle valve(s). The valve permits a regulated amount of exhaust gas to enter the inlet duct and mix with the incoming air/fuel mixture.

The only way the EGR valve will open is when vacuum is applied through its vacuum hose. When vacuum is applied, it raises a diaphragm inside the EGR valve. This diaphragm is connected to a plunger inside the EGR valve housing. When the plunger is open, it allows exhaust gases to pass through the pipe between the valve and the intake manifold. When the exhaust gases mix with the air/fuel charge in the combustion chamber, they act to slightly slow the rapid combustion process and lower the overall combustion chamber temperature. This lower combustion temperature prevents the formation of oxides of nitrogen (NOx).

On 1974-75 B20 engines, 1976 B21 and B27 models sold in California and all later models with EGR valves, the EGR system is modified to improve cold start driveability by the addition of a venturi vacuum amplifier system.

The EGR system with vacuum amplifier works as follows: venturi vacuum at the air intake is used to measure the total air flow. This weak vacuum signal controls the vacuum amplifier which regulates the EGR valve via a solenoid valve. The vacuum amplifier receives inputs both from the strong intake manifold source which is used as a power source, and from the weak air intake source which is to be amplified. The intake vacuum is stored in the vacuum reservoir and is controlled by a check valve in the amplifier. This allows a generous amount of vacuum on tap, regardless of variations in engine manifold vacuum.

The amplifier then continues to supply adequate vacuum at higher speeds and moderate throttle openings, when manifold vacuum normally would drop to an insufficient amount. The EGR system functions as before, except that the exhaust gases are prevented from recirculating at idle and full throttle by a throttle angle sensing micro-switch and an electrically operated solenoid valve, rather than simple vacuum as in 1973. On 1976 and later models, a wax thermostat blocks exhaust gas recirculation until the engine warms to 140°F (60°C).

Beginning with the 1975 model year, all Volvos equipped with an EGR system have a reminder light which is actuated by the odometer at 15,000 mile (24,155 km) intervals. The light may be reset by pressing a white button at the rear of the odometer.

Models equipped with the Lambda Sond oxygen sensor system do not have EGR valves. All 1978-80 California models, as well as 1980 and later 49 states models, are not equipped with EGR valves.

SERVICE



Check and clean the system every 12 months/12,000 miles (19,324 km) for 1973-74 vehicles, or 12 months/15,000 miles (24,155 km) for 1975-83 vehicles. Replace the EGR valve, if equipped, every 24 months/24,000 miles (38,647 km) for 1973-74 vehicles, or 24 months/30,000 miles (48,309 km) for 1975-83 vehicles.

CHECKING



All 1973 Models and 1975 164

The EGR valve and piping conducts exhaust gases; for this reason, the system components are exposed to high temperatures, corrosion and soot. It is not uncommon for an EGR valve to become plugged with carbon. When this happens, the valve cannot close completely. Since there are times that recirculation is not desirable, having the valve stick open causes a variety of driveability problems including poor mileage, lack of power and rough idle. Checking the EGR valve and replacing it on schedule should be a part of your routine maintenance plan.

With the engine warmed up and idling, remove the EGR vacuum hose from the valve and plug it (a wooden golf tee works well), then apply vacuum with a hand-held vacuum pump to the vacuum port on the valve. The engine should stumble or stall, indicating the EGR valve is open. If not, replace the EGR valve.

1974 140 Series and 1975 240 Series

See Figure 4

  1. Start the engine and let it idle.
  2.  
  3. Remove the air intake hose from the vacuum amplifier at connection number 1.
  4.  
  5. Connect a vacuum pump or other suction device to outlet number 1 on the vacuum amplifier.
  6.  
  7. Apply vacuum: the EGR valve should NOT open (the idle should not stumble or the engine stall).
  8.  
  9. Check that the system holds a vacuum for about 10 seconds.
  10.  
  11. With the vacuum still applied to outlet number 1 on the vacuum amplifier, disconnect the wire from the micro-switch at the throttle linkage. The EGR valve should open, so that the engine runs poorly or stalls. The micro-switch "tells" the system that the engine is at idle; by disconnecting the switch, the system reacts as if the engine were under acceleration. The EGR system engages.
  12.  
  13. Reconnect all components and increase engine speed. Visually check that the EGR valve opens. Drop the engine to idle: the EGR valve should close.
  14.  
  15. To adjust the micro-switch, unplug the micro-switch electrical connection and hook up a test light between the switch and its electrical connection. Turn on the ignition.
  16.  



Click image to see an enlarged view

Fig. Fig. 4: Adjust the micro-switch to the proper tolerance-B20 engines

  1. Back off the adjustment screws on both the micro-switch and the throttle plate. To adjust the throttle plate, turn in its screw until it just touches the stop, then turn it 1 / 2 turn more. Secure its locknut.
  2.  
  3. Insert a 0.060 in. (1.5mm) for the 240 series, or a 0.040 in. (1.0mm) for the 140 series, feeler blade under the throttle stop screw. The test light should not light. Turn in the micro-switch screw until the light just turns on. You will hear the switch click. Secure the lock nut, remove the gauge and reconnect the micro-switch wire.
  4.  

1976-83 Models
Without Vacuum Amplifier

See Figure 5

Models equipped with the Lambda Sond oxygen sensor system do not have EGR valves. 1978-80 California models, as well as 1980 and later 49 states models, are not equipped with EGR valves. Therefore, portions of the following procedure may not apply to your vehicle.

  1. With the engine cold, check the operation of the wax thermostat. Start the engine and allow it to idle. Manipulate the throttle by hand and check that the EGR valve rod does not move in and out. If it does, the thermostat is faulty. It should not operate the EGR valve until the coolant reaches 130-140°F (54-60°C).
  2.  
  3. With the engine warmed up to normal operating temperature-176°F (80°C)-check that the EGR valve rod does move in and out then the throttle is opened and closed. If not, the wax thermostat, hoses or EGR valve may be at fault.
  4.  



Click image to see an enlarged view

Fig. Fig. 5: Check to see if the rod inside the EGR valve moves in and out

  1. Stop the engine. Disconnect the vacuum hose from the EGR valve. Blow through the hose. If no air passes, the wax thermostat is faulty. If air does pass, either the hose is incorrectly installed or the EGR valve is defective.
  2.  
  3. Finally, connect the EGR vacuum hose and start the engine. Open the throttle to 3000-4000 rpm and then quickly release it. The EGR valve rod should close. If not, replace the EGR valve.
  4.  

With Vacuum Amplifier

See Figures 6 and 7

Use the illustrations to identify the vacuum amplifier; it will be located in the engine compartment.

  1. With the engine cold-below 130°F (54°C)-coolant temperature, check the operation of the wax thermostat. Disconnect the vacuum hose at the solenoid valve and disconnect the vacuum hose at the vacuum amplifier connection S. Draw suction on one of the disconnected hoses. If any air passes, one of the hoses has a vacuum leak or the wax thermostat is faulty. Reconnect the hoses.
  2.  



Click image to see an enlarged view

Fig. Fig. 6: Check the operation of the wax thermostat-1976 and later models

  1. Start the engine and warm up to normal operating temperature (176°F). Stop the engine. Disconnect the two hoses again and draw suction through either of the hoses. This time the thermostat should be open, and air should pass through. If not, replace the wax thermostat.
  2.  
  3. Connect the hoses, then check the throttle position sensing micro-switch, as follows:
    1. Connect a 12V test light in series between the upper wire connector and its upper terminal. Switch the ignition to the ON position.
    2.  
    3. Pull back the throttle lever and insert a 0.060 in. (1.5mm) feeler gauge between the screw and the lever stop. When the lever is released and the throttle screw makes contact with the switch plunger, the test light should illuminate. This indicates that current is reaching the solenoid valve, the micro-switch is activating, and the fuse is good.
    4.  
    5. Repeat by inserting an 0.080 in. (2mm) feeler gauge between the screw and lever stop. This time, the test light should not light and the throttle screw should not make contact with the switch plunger. Adjust as necessary by loosening the locknut on the stopscrew and adjusting for 0.060 in. (1.5mm) clearance.
    6.  

  4.  



Click image to see an enlarged view

Fig. Fig. 7: Use a feeler gauge to check the micro-switch adjustment-B27F engine shown

Models equipped with the Lambda Sond oxygen sensor system do not have EGR valves. 1978-80 California models, as well as 1980 and later 49 states models, are not equipped with EGR valves. Therefore, portions of the following procedure may not apply to your vehicle.

  1. Check the solenoid valve next. With the engine running at idle, disconnect the hose from connection 1, and create a vacuum. The EGR valve, if so equipped, should remain closed (no change in rpm). If not, the solenoid valve is defective.
  2.  
  3. With the vacuum pump still connected, and engine idling, check that the vacuum reading does not change for 10 seconds. If the reading changes, this indicates a bad amplifier or leaking hoses.
  4.  
  5. Finally, with the engine idling, increase the rpm while observing the EGR valve (if so equipped). If the EGR valve rod does not open, check for clogged venturi or leaking venturi vacuum hose. After increasing engine speed to about 2500 rpm, suddenly release the throttle and check that the EGR valve rod closes. If it does not, the solenoid valve is faulty.
  6.  

REMOVAL & INSTALLATION



The EGR valve simply unbolts from the two pipes it connects. Always use two wrenches to free the couplings or you may bend the pipes. If it is necessary to replace the valve, check the part number stamped on the body of the old valve and install an exact match. An incorrect valve may add to the problems you're trying to cure.

The EGR valve may be cleaned by removing it and tapping it lightly with a soft mallet. This dislodges built-up carbon which may be fouling the plunger. Do NOT clean the valve with solvents; this will damage the diaphragm within. Make sure that the ports and pipes are clean and free of carbon. When cleaning or inspecting the EGR valve, hold it in your hand. Mounting it in a vise may deform it and impair its function.

 
label.common.footer.alt.autozoneLogo