F 100 2WD Pickup V8-400 6.6L (1982)
Vacuum Delay Valve: Testing and Inspection
Delay Vacuum Bypass (DVB)
1.
Remove air cleaner.
2.
Remove spark delay valve. (Refer to Spark Delay Valve section for test procedure for this unit.) Replace spark delay valve with a connector.
Remove vacuum line at distributor and install a vacuum line at distributor and install a T-fitting and a vacuum gauge.
3.
With transmission in neutral and engine idling at normal operating temperature, open throttle to 1/2 open position.
4.
Open and close throttle as noted in Step 3 while watching vacuum reading. A quick rise and fall should be noted. If vacuum is indicated, check the
vacuum lines, evaporative canister purge valve. T-fitting, and carburetor vacuum port for blockage. Correct as necessary.
5.
Turn off engine and replace the spark delay valve (tested before reinstalling as noted in Step 2). Remove vacuum gauge and T-fitting and replace
vacuum hoses.
6.
Remove vacuum check valve and test. (Refer to Spark Delay Valve section for test procedure for this unit). Replace if defective. Reinstall valve.
7.
Install a T-fitting between the check valve and the PVS. Connect a vacuum gauge at this point.
8.
With transmission in neutral and engine idling at normal operating temperature, open throttle to 1/2 position. Note vacuum reading at steady 1/2
throttle. If reading is 2 inches Hg or less, PVS unit is good. If more than 2 inches Hg is indicated, PVS is defective and must be replaced.
9.
Remove vacuum gauge and return all vacuum lines to original location. Reinstall air cleaner assembly.
