Exhaust Gas Recirculation: Testing and Inspection

Testing The EGR System:

EGR SYSTEM TEST

COLD ENGINE TEST - Coolant temperature is below 45°C (113°F)

1. Disconnect the green striped vacuum hose from the carburetor throttle body and connect it to a hand vacuum pump.
2. With the engine rpm at 3,500, try applying vacuum.
Vacuum should leak from the thermo valve.

WARM ENGINE TEST - Coolant temperature is above 85°C (185°F)
1. Disconnect the green striped vacuum hose from the carburetor throttle body and connect it to a hand vacuum pump.
2. With the engine idling, apply vacuum.
Vacuum should leak.
3. Disconnect the yellow striped hose from the carburetor throttle body, and plug the hose.
4. Again, apply vacuum to the green striped hose.
Vacuum should hold and engine rpm should become unstable.
5. Increase engine rpm to 3,500, and apply vacuum.
Vacuum should leak down until it reaches 3.1 in.
If the test results differ, the EGR passages may need to be cleaned, or the EGR valve may need to be replaced. Continue diagnosis of the EGR system components.
Refer to MAINTENANCE PROCEDURES for EGR SYSTEM cleaning.

EGR VALVE INSPECTION

1. Remove the EGR valve and check it for sticking or carbon deposits.
If such condition exists, refer to MAINTENANCE PROCEDURES for EGR Control Valve and EGR Passages cleaning.

Testing The EGR Valve:

2. Connect a hand vacuum pump to the EGR vacuum nipple.
If there is more than one nipple, the second nipple will need to be plugged for this test.
3. Apply 19.7 in. vacuum to the vacuum chamber of the EGR valve.
Vacuum should not leak from vacuum chamber. Release vacuum.
4. Apply 2.4 in. of vacuum. Blow air in from one side of the valve.
Air should not pass through
5. Increase vacuum to 6.7 in. while blowing air through EGR passage.
Air should pass through.

Testing The Thermo Valve:

THERMO VALVE

NOTE: When disconnecting the vacuum hoses, mark or label them to ensure proper routing when being reconnected.

1. Disconnect the vacuum hoses from the thermo valve.
2. Connect a hand vacuum pump to the thermo valve, apply vacuum.
If coolant temperature is below 50°C (122°F) vacuum should leak.
If coolant temperature is above 65°C (149°F) vacuum should hold.

Testing The Vacuum Regulator Valve:

VACUUM REGULATOR VALVE (VRV)

With the engine stopped.
1. Disconnect the white stripe vacuum hose from the device box.
2. Connect a hand vacuum pump to the nipple which the hose was connected to.
3. Try applying vacuum. Vacuum should not hold.
4. Start the engine and increase the rpm to 3,500.
5. Apply 15.7 in. of vacuum. Vacuum should hold.

Vacuum Nipples On Carburetor:

VRV CONTROL VACUUM CHECK

With engine coolant temperature at 95°C (205°F)
1. Disconnect the vacuum hose from the carburetor "A" vacuum nipple.
2. Connect a hand vacuum pump to the nipple.
3. Start and race the engine.
4. Check to ensure that "A" vacuum increases gradually with the engine rpm.