26
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.
Todays 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.
