Lambda O2 Sensor Co Adjustment With MONOTESTER (GROUP 24, NO. 113)

WARNING: This page is about the 760 GLE, 2.4 76, Automatic, which is a different variant/trim than selected.

Publication date: 1985-05-01
Reference number: GROUP 24, NO. 113

LAMBDA O2 SENSOR CO ADJUSTMENT WITH MONOTESTER

TECHNICAL SERVICE BULLETIN

Reference Number(s): GROUP 24, NO. 113, Date of Issue: May, 1985
Superceded Bulletin(s): Group 24, Number 113, Date of Issue: March, 1983

LAMBDA DUTY CYCLES (CO ADJUSTMENT AND FUNCTION TEST WITH THE VOLVO MONOTESTER)

Model(s): 1983-84 Volvo 700 w/ B28F, B23FT, B230, B230FT Engine

Group: 24

Bulletin No.: 113

Date: May, 1985

NOTE: This bulletin supersedes Service Bulletin Group 24, Number 113 dated March, 1983.

SERVICE INFORMATION

Lambda duty cycles, function tests and CO adjustments can be performed on all Volvo engines equipped with a Lambda Sensor System with the aid of the Volvo MONOTESTER (P/N 9999921-1). This method does not require the normal connection(s) to the exhaust system; therefore, labor time is reduced considerably.

CONNECTING THE MONOTESTER

Connect the monotester, as described in the operating manual, but note that the blue lead must be connected to the Lambda service pickup, which is located at the firewall on P70 MY 1983 and at the right wheel housing on P70 MY 1984 and later. See Fig 1 .

NOTE: When driving the vehicle with the monotester connected, the positive (red) lead must be increased in length by 60mm (24").

Fig 1: Lambda Service Pickup

MODE AND SCALE SELECTION

Set the MONOTESTER switch as shown in Fig 2 .

Fig 2: Setting Monotester

Use the four cylinder "dwell" position, 70° and read the dwell scale.

TESTING OPEN LOOP, B28F (CI)

Disconnect the green wire from the Lambda sensor. See Fig 3 . With the engine at normal operating temperature, the reading must be stable at 45 +/- 2 degrees.

NOTE: Applies only to CI engines. The reading for LH-Engines may vary with the sensor disconnected.

Fig 3: Lambda Sensor Wire

If the reading of the MONOTESTER shows an incorrect value, check the following:

Check that the frequency valve is buzzing.
Wiring and connector continuity.

Fig 4: Frequency Valve

TESTING LAMBDA CONTROL FUNCTION (ALL ENGINES)

Ground the green wire from the control unit (at the firewall). See Fig 5 .

Fig 5: Grounding Control Unit Wire

The pointer on the MONOTESTER should move to:

B28F (CI) - 70 degrees or above
B23FT, B230FT, B230F - 0 degrees. See Fig 6 .

Fig 6: Monotester Readings

Reconnect the green wire to the Lambda sensor.

CO-CHECK AND ADJUSTMENTS

Connect the lambda sensor.

Warm up the engine to normal operating temperature. Check that ignition timing and idle speed are within specification. Adjust when necessary.

Check the "dwell" reading on the MONOTESTER. The reading should not be stable. With the correct CO setting, the reading should fluctuate around the following values:

B28F (CI) - 43 degrees (41-44)

B23FT, B230FT, B230F (LH) - 20-70 degrees

ADJUSTMENT

B28F (CI): A high reading indicates a lean mixture and the CO adjustment screw should be turned clockwise. A low reading indicates a rich mixture and the CO adjustment screw should be turned counter-clockwise.

B23FT, B230FT, B230F (LH): A high reading indicates a rich mixture and the CO adjustment screw should be turned counter-clockwise. A low reading indicates a lean mixture and the CO adjustment screw should be turned clockwise.

The adjustment range on LH-Engines is 15 turns on the CO adjustment screw. The range where the pointer fluctuates on LH engines is equivalent to one turn on the CO adjustment screw.

NOTE: The emission regulations in the U.S. and Canada require access to CO-adjustment be sealed. After adjustment, the CO-adjustment must be resealed.

ENRICHMENT SYSTEMS B28F (CI)

The CI-system for B28F is equipped with inter-related enrichment systems:

Cold start enrichment system
Acceleration enrichment system.
Full load enrichment system

These systems can also be checked with the use of the Monotester.

COLD START ENRICHMENT SYSTEM

This system is only engaged, when the coolant temperature is below +15 degrees C (+60 degrees F). This system can also be checked at temperatures above +15 degrees C (+60 degrees F) by grounding terminal 7 at Lambda control unit. The reading,when activated,should be 52 - 56 degrees.

ACCELERATION ENRICHMENT SYSTEM

This function is only engaged at coolant temperatures below 53°C (+127°F).

This system should be checked with a cold engine, but can also be checked with the engine at normal operating temperatures.

PROCEDURE

Connect a vacuum pump to the pressure differential switch and evacuate switch. See Fig 7 .
Release vacuum. When vacuum is released, the switch closes. The dwell meter reading should change to 70 degrees or above for a short period and then decrease.

Fig 7: Pressure Differential Switch

NO READING OR INCORRECT READING

Connect a jumper wire between the pins in the connector, as shown in Fig 8 .

If meter now reads 70 degrees or above, wiring and control unit is OK.

Check vacuum hoses (replace if applicable).
Check thermo valve.
Check differential switch.

Fig 8: Pressure Differential Switch Connector

FUNCTION CHECK

On the B28F engines, this system can be tested by "closing" the microswitch at the throttle pulley. The reading should be 54 +/- 2 degrees. See Fig 9 .

Fig 9: Microswitch

NO READING OR INCORRECT READING

Check wiring/connector continuity.
Check microswitch.
Check control unit.