Chart A-1 Dwell Fixed Under 10 Degrees

- Chart A-1 Dwell Fixed Under 10 Degrees.:

- Wiring Diagram for A-1 Dwell Fixed Under 10 Degrees.:

CHART A-1, DWELL FIXED UNDER 10°

LEAN EXHAUST INDICATION

CHART DESCRIPTION
1. Determines if the problem is CCC related or engine related.
Dwell should start increasing as soon as engine is choked, and go higher as it is choked more, until it goes over 50°. With severe choking, the dwell could move up scale momentarily even if it is not engine related, but it will move right back to a low dwell. If dwell responds, the problem is a lean engine.
1a. Checks for cause of lean condition that resulted in full rich command.
2. Checks for ECM response to input to O2 sensor circuit. The voltmeter is used to put a voltage on the oxygen sensor circuit to simulate a rich condition. Dwell should increase (a lean command) if ECM and harness are good.
3. Checks for normal coolant sensor circuit condition. Voltage on a normalized hot engine should be under 2.5V.
4. This step checks for an open in the ground circuitto ECM Term. "14" and grounded O2 sensor circuit.
Terminal "2" voltage should be under 1.0 volt at idle. A high voltage could be caused by an open in the circuit at Term. "22". Normally, this would cause Codes 21 and 34 (and 35 if equipped with idle speed control) but won't set them on some engines.