Hot Engine

Disconnect vacuum hose from EGR valve and connect vacuum gauge to hose. Push a voltmeter positive probe into the terminal at the control box connector (Yellow/White on 1500, Gray on 1300 models). Connect the negative probe to ground.

On 1300 models, jack up the front of the vehicle. Support with safety stands, block rear wheels, and set hand brake. Start and warm up engine (cooling fan must come on). On all models, vacuum and voltage should be as follows:

EGR SYSTEM TEST

Engine Condition & No.

EGR Valve Vacuum

Specified Wire Voltage

All Models

1 Idle

⁽¹⁾ No

2 4500 RPM 1500 Models

Yes

3 Hard Acceleration (Plug Hose # 12)

1-3 in. Hg

Yes

1300 Models

3 Hard Acceleration over 10 MPH ⁽²⁾

2-6 in. Hg

Yes

⁽¹⁾	Yes on 1500 model.

⁽²⁾	In second gear.

If vacuum is available for condition 1, check vacuum hose routing. If no problem found, replace EGR control valves A and B.
If there is no vacuum available for condition 2 and 3, connect voltmeter to EGR control solenoid B (Yellow/White on 1300 or Blue on 1500 models). Recheck for voltage according to conditions 2 and 3 in EGR System Test.
If voltage is present on 1300 models, check thermosensor. See Trouble Shooting in this article. If voltage is present on 1500 models, check control unit voltage, ground and vacuum switch A. See Trouble Shooting in this article.
If no voltage is present, check for vacuum at 4500 RPM at EGR control solenoid valve A. If no vacuum is available, check vacuum hose routing and carburetor port. If vacuum is available, replace EGR control solenoid valve A and retest.
If there is no voltage available for condition 2 but vacuum is greater than 3 in. Hg, replace the EGR control valve B.
On 1300 models, if there is no voltage available for condition 1, 2 or 3, check the speed sensor. See Trouble Shooting in this article. On 1500 models, if there is no voltage available for condition 1, 2 or 3, check the control unit voltage, ground and vacuum switch A. See COMPONENT TESTING .