With engine in Neutral, set carburetor to fast idle position. Remove spark delay valve and connect a vacuum gauge to the vacuum hose leading to the carburetor. Record vacuum, it should be between 10"-16" Hg. for tests. Pinch off vacuum hose to gauge and observe if gauge maintains vacuum level. If vacuum drops with hose pinched off, gauge or vacuum hose has an external leak which must be corrected.
After completing Step 1, connect BLACK side of spark delay valve to vacuum hose leading to carburetor. Connect vacuum gauge to hose leading from DISTRIBUTOR side of spark delay valve. Start engine, and with carburetor set to fast idle position, note time in seconds for gauge to reach 6" Hg. with a 10"-16" Hg. vacuum source.
Maximum time for each type valve to reach 6" Hg. should be as follows:

Time in Seconds

NOTE: If vacuum reaches 6" Hg. level in less than two seconds, valve, regardless of type, must be replaced.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Spark Delay Valve System: Testing