Lambda Testing W/ Volt, Dwell, RPM and CO Meter

To test the Lambda sond, all potential problems influencing a Lambda sond reading (ignition, fuel injection, intake and exhaust system etc.) must be checked and corrected.

To test the function of the Lambda sond follow the next procedures step by step:

Fig. 78 DISCONNECT LAMBDA SOND:

1. Disconnect Lambda sond. Fig. 78.

Fig. 77 Lambda Service Pick-up:

2. Connect a tachometer.
3. Connect a dwell meter to test point at the firewall.
4. Set the meter for testing a 4-cylinder engine. Fig. 77.


NOTE:
The dwell meter must have a minimum measuring range of 70°.
Instruments such as the "Volvo Mono-Tester" and "Sun" testers of later design are recommended.

Fig. 80 CONNECT CO-METER:

5. Connect a CO meter with Volvo connector #5151 (connector lever should be in center position) or T-type connector. Fig. 80.


6. Warm up engine until 5 minutes after the thermostat has opened.
7. Check idle speed (900 +/- 20 RPM) and adjust if necessary.
8. Check CO content (0.7 - 1.3%) and adjust if necessary.

NOTE:
Air conditioner must be off.

Fig. 81 CHECK LAMBDA SOND FUNCTION:

9. Connect Lambda sond and read the dwell and CO meter.
Dwell meter reading should change slightly, normally reduce. CO content must drop below 1%. Fig. 81.

Fig. 82 CHECK LAMBDA SOND FUNCTION:

If neither CO content nor meter reading changes:
-Disconnect Lambda sond and ground the wire. CO content and dwell angle should increase. Fig. 82.
-Wiring and control unit are O.K. if meter reading increases.
-Replace and re-test with new Lambda sond.
- If meter reading does not change, either control unit or wiring to control unit is defective. Check wiring to control unit, if O.K. replace control unit.

C.O. content and dwell meter reading increase:
-This indicates a defective Lambda-sond (internal short). Replace and re-test with new Lambda sond.