Troubleshooting

Fig.151 - Vacuum & Voltage Chart:

1. If voltage is available for operating conditions 1, 2, or 3, check thermosensor for continuity. If it has continuity replace it and then retest.
2. Should it not have continuity, then remove line from control switch, connect it to a vacuum gauge. If there is no vacuum at an idling speed, replace the control switch and retest.
3. In the case of the control switch having vacuum at idle, then check for voltage to the throttle opener solenoid. With the ignition on, there should be no voltage, if so, then replace and retest.
4. Should there be voltage, replace speed sensor and retest.
5. No voltage available but vacuum for operating condition 1 or vacuum greater then 2" Hg for condition 3, replace EGR control valves, also verify vacuum hose routing.
6. If voltage is available for condition 4, then check control switch.
7. No voltage available for condition 5, check control switch. With speed sensor jumped and engine at idle, remove vacuum line at control switch and check for vacuum. If vacuum is available, reconnect line and check for voltage at EGR control solenoid valve. There should be voltage. If there should be no voltage then replace the control switch and retest.
8. No vacuum and no voltage available for condition 2 and 4, check for ported vacuum running at 4,500 RPM at EGR control solenoid valve inlet. Should no vacuum be available, check vacuum line routing and the carburetor pert, clean, retest. If vacuum is available, replace EGR control solenoid valve.
9. Vacuum and voltage available for condition 5, replace EGR control solenoid valve.