Exhaust Gas Recirculation: Testing and Inspection

COLD ENGINE

Note: Engine coolant temperature must be below set temperature of thermosensor A and thermosensor A must have continuity.






1. Disconnect vacuum hose from EGR valve and connect vacuum gauge to hose.
2. Start engine and raise engine speed to 4500-5000 RPM.
Vacuum should be available:
If vacuum is not available, proceed to hot engine inspection.
If there is vacuum, check for voltage at EGR control solenoid valve A (box #2, blue wire).
There should be voltage:
If there is voltage, replace EGR control solenoid valve A and retest.
If there is no voltage, check thermosensor A operation, wiring, fuses and retest.

HOT ENGINE

1. Disconnect vacuum hose from EGR valve and connect vacuum gauge to hose.






2. Push voltmeter positive probe into blue terminal control box #2 connector and connect negative probe to suitable ground.
3. Raise and support front of vehicle, block rear wheels, and apply hand brake.
4. Start engine and wait for engine to warm up; cooling fan must come on.

Fig. 64 Vacuum & voltage chart.:

Vacuum and voltage should be as shown in chart. If readings are not correct, refer to the appropriate troubleshooting conditions as follows:

1. Voltage is available for conditions 1, 2 or 3:

Check thermosensor for continuity.
If there is continuity, replace thermosensor and repeat test.






If there is no continuity, disconnect hose from control switch (located in control box #1) and connect vacuum gauge to hose.
There should be no vaccum at idle.

If there is no vacuum at idle, replace control switch and repeat test.






If there is vacuum at idle, check for voltage (yellow/black wire) to the control switch solenoid valve.

If there is no voltage to valve with ignition switch on, replace control switch solenoid valve and repeat test.
If there is voltage, replace speed sensor and repeat test.

2. No voltage is available but vacuum is available for condition 1 or vacuum is greater than 2 in. hg. for condition 3

Replace EGR control valves A and B (in box #1) and verify vacuum hose routing.

3. Voltage is available for condition 4

Replace control switch (in box #1).

4. No voltage is available for condition 5

Check control switch. Engine at idle with speed sensor jumpered, disconnect vacuum line at control switch and check for vacuum.
If vacuum is available, reconnect vacuum line and check for voltage at EGR control solenoid valve A. There should be voltage. If there is no voltage, replace control switch and repeat test.

5. No vacuum or voltage available for conditions 2 & 4

Run engine at 4500 RPM and check for ported vacuum at inlet of EGR control solenoid valve A.
If there is no vacuum, check vacuum hose routing and carburetor port. Correct as necessary and repeat test.
If there is vacuum, replace EGR control solenoid valve A (in box #2).

6. Vacuum & voltage are available for condition 5

Replace EGR solenoid valve A (in box #2).