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Testing GM C-3 Mixture Control Solenoid Dwell

This solenoid is located in the carburetor. Its

purpose is to maintain an air/fuel ratio of 14.7

to 1 in order to reduce emissions. This test

checks to see if the solenoid dwell is varying.

Test Description:

This test is rather long and detailed. Refer to

vehicle service manual for the complete test

procedure. Some important test procedure

highlights you need to pay close attention to

are listed below.

1. Make sure engine is at operating

temperature and running during test.

2. Refer to vehicle service manual for

multimeter hook-up instructions.

3. Turn multimeter rotary switch to 6

Cylinder Dwell position for all GM

vehicles.

4. Run engine at 3000 RPM.

5. Make engine run both RICH and LEAN.

6. Watch multimeter display.

7. Multimeter display should vary from 10

°

to 50

°

 as vehicle changes from lean to

rich.

Typical Mixture Control

Solenoid Connection

Mixture Control

Solenoid

Fuel System Testing

The requirements for lower vehicle emissions has

increased the need for more precise engine fuel control.

Auto manufacturers began using electronically controlled

carburetors in 1980 to meet emission requirements.

Today’s modern vehicles use electronic fuel injection to

precisely control fuel and further lower emissions. The

digital multimeter can be used to test the fuel mixture

control solenoid on General Motors vehicles and

to measure fuel injector resistance.

Summary of Contents for Digital Multimeter CP7676

Page 1: ...Air Flow MAF Sensors 34 Index Safety Precautions 2 Vehicle Service Information 3 Visual Inspection 3 Electrical Specifications 35 Warranty 72 1 Multimeter Basic Functions Functions and Display Defini...

Page 2: ...ge when the engine is running Always turn ignition key OFF when connecting or disconnecting electrical components unless otherwise instructed Always follow vehicle manufacturer s warnings cautions and...

Page 3: ...reconnected in the wrong place or not at all Don t take shortcuts Inspect hoses and wiring which may be difficult to see due to location Inspect the air cleaner and ductwork for defects Check sensors...

Page 4: ...n defines these features and functions and explains how to use these functions to make various measurements 1 Alligator Clip Adapters Some multimeter tests and measurements are more easily done using...

Page 5: ...s used for measuring DC Direct Current Voltages in the range of 0 to 200V 8 AC VOLTS This Function is used for measuring AC Alternating Current Voltages in the range of 0 to 750V 9 DISPLAY Used to dis...

Page 6: ...or in other words the value being measured is larger than the current range The range should be increased until a value is shown on the display If you are in the highest range and the multimeter is s...

Page 7: ...d electrical wiring and appliances To measure AC Voltages 1 Insert BLACK test lead into the COM test lead jack 2 Insert RED test lead into the V test lead jack 3 Connect RED test lead to either side o...

Page 8: ...ad jack 3 Connect RED test lead to positive side of voltage source 4 Connect BLACK test lead to negative side of voltage source NOTE If you don t know which side is positive and which side is negative...

Page 9: ...n or shorted wires To measure Continuity see Fig 9 1 Insert BLACK test lead into the COM test lead jack 2 Insert RED test lead into the test lead jack 3 Turn multimeter rotary switch to 200 range 4 To...

Page 10: ...election 6 Measure engine RPM while engine is cranking or running 7 View reading on display Fig 11 Black Ground Red Typical Ignition Coil 1 Insert BLACK test lead into the COM test lead jack 2 Insert...

Page 11: ...2 Insert RED test lead into the test lead jack 3 Connect RED test lead to DWELL signal wire If measuring DWELL on breaker point ignition systems connect RED test lead to negative side of primary ignit...

Page 12: ......

Page 13: ...to see if a switch Opens and Closes properly To test Switches see Fig 14 1 Insert BLACK test lead into the COM test lead jack 2 Insert RED test lead into the test lead jack 1 Insert BLACK test lead i...

Page 14: ...jack 2 Insert RED test lead into the V test lead jack 3 Turn multimeter rotary switch to 200 range Most solenoids and relay coil resistances are less than 200 If meter overranges turn multimeter rota...

Page 15: ...any starting charging system checks you must first test the battery to make sure it is fully charged 4 Insert RED test lead into the V test lead jack 5 Disconnect positive battery cable 6 Connect RED...

Page 16: ...below Fig 17 Voltage Temperature 9 6V or greater 70 F and Above 9 5V 60 F 9 4V 50 F 9 3V 40 F 9 1V 30 F 8 9V 20 F 8 7V 10 F 8 5V 0 F If voltage on display corresponds to above voltage vs temperature...

Page 17: ...h this test you can find excessive resistance in the starter system This resistance restricts the amount of current that reaches the starter motor resulting in low battery load voltage and a slow cran...

Page 18: ...Load the electrical system by turning on the lights windshield wipers and setting the blower fan on high 11 View reading on display Voltage should not drop down below about 13 0V 12 Shut off all acce...

Page 19: ......

Page 20: ...teps 6 and 7 for remaining ignition coils Fig 20 Fig 21 Black Secondary Coil Primary Coil Red 4 Insert RED test lead into the V test lead jack 5 Turn multimeter rotary switch to 200 range Touch RED an...

Page 21: ...ry ignition coils is 6 0 30 0K Refer to vehicle service manual for your vehicles resistance range 15 Repeat test procedure for a HOT ignition coil NOTE It is a good idea to test ignition coils when th...

Page 22: ...sult if other means of removal are attempted Refer to vehicle service manual for procedure NOTE Some spark plug wires have sheet metal jackets with the following symbol This type of plug wire contains...

Page 23: ...hicle service manual for pin locations 3 Insert BLACK test lead into the COM test lead jack 4 Insert RED test lead into the V test lead jack 5 Connect RED test lead to sensor SIGNAL pin 6 Connect BLAC...

Page 24: ...or Fig 24 Test Procedure see Fig 24 1 Insert BLACK test lead into the COM test lead jack 2 Insert RED test lead into the V test lead jack 3 Connect RED test lead to either sensor pin 4 Connect BLACK t...

Page 25: ...e to the vehicle engine computer refer to vehicle service manual for location of this wire For all vehicles with distributors connect RED test lead to negative side of primary ignition coil refer to v...

Page 26: ...ltimeter rotary switch to 6 Cylinder Dwell position for all GM vehicles 4 Run engine at 3000 RPM 5 Make engine run both RICH and LEAN 6 Watch multimeter display 7 Multimeter display should vary from 1...

Page 27: ...correct units If display reading is 10 or less subtract test lead resistance found in Step 3 from above reading Compare reading to manufacturers specifications for fuel injector coil resistance This i...

Page 28: ...nce indicates a lean exhaust too much oxygen while a high voltage low resistance indicates a rich exhaust not enough oxygen The computer uses this voltage to adjust the air fuel ratio The two types of...

Page 29: ...ame to deplete sensor of oxygen Rich Condition Multimeter display should read 0 6V or greater for Zirconia Type Sensors an Ohmic Resistance value for Titania Type Sensors Reading will vary with flame...

Page 30: ...nsors leave multimeter test leads still connected to sensor 11 Heat up sensor If testing Intake Air Temperature Sensor To heat up sensor dip sensor tip into boiling water or Heat tip with a lighter if...

Page 31: ...see Fig 29 1 Insert BLACK test lead into the COM test lead jack 2 Insert RED test lead into the V test lead jack 3 Disconnect wiring harness from sensor 4 Connect Test Leads Connect RED test lead to s...

Page 32: ...ce as sensor is opened and closed Bad Sensor There is no change in resistance as sensor is opened or closed 32 Manifold Absolute Pressure MAP and Barometric Pressure BARO Sensors This sensor sends a s...

Page 33: ...frequency type MAP sensors refer to vehicle service manual for MAP sensor specifications It is O K if last two display digits change slightly while vacuum is held constant Remember to multiply displa...

Page 34: ...e ground 4 Connect RED test lead to MAF signal wire Refer to vehicle service manual for location of MAF signal wire You may have to backprobe or pierce MAF signal wire in order to make connection Refe...

Page 35: ...RPM conversions 9 Test Results Good Sensor Sensor output voltage or frequency RPM are within manufacturers specifications at Key ON Engine OFF Sensor output voltage or frequency RPM increase with inc...

Page 36: ...36...

Page 37: ...te GARANTIA COMPLETA DE UN A O SPX Corporation 15825 Industrial Parkway Cleveland Ohio 44135 EE UU garantiza al usuario que esta unidad estar libre de defectos de materiales y mano de obra por un 1 a...

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