Nova/Chevy II L4-1600cc 4ALC Nummi (1988)
Distributor Vacuum Control: Testing and Inspection
Control Switches & Valves
Distributor Vacuum Modulator Valve (DVMV)
This valve has a calibration point of 8.7 inches Hg. Whenever the manifold or ported vacuum is less than 8.7 inches, the DVMV switches to full
manifold vacuum. Whenever manifold or ported vacuum is greater than 8.7 inches Hg, the DVMV switches to the highest vacuum, either ported or
manifold.
Vacuum Reducer Valve (VRV)
1.
Connect a vacuum gauge to the outlet port of the valve and a hand operated vacuum pump to the inlet port.
2.
Apply 15 inches Hg vacuum. The reading at the outlet port should be 1 1-2 inche slower and should read 13 to 13 1-2 inches Hg.
3.
If the valve is not seating and bleeding off to vent, replace valve. If valve is defective, engine idle will be rough and driveability of the vehicle
will be affected.