If the purge control solenoid has been bypassed, which entry should be made in the EVAP system during testing?

• A. Enter the EVAP system as modified; both CO and HC would increase.
• B. Enter the EVAP system as original; CO and HC would decrease.
• C. Enter the EVAP system as modified; CO would increase but HC would decrease.
• D. EVAP system bypassed; emissions data not recorded.

Answer: (A)

When testing EVAP and the purge system, you must account for how changes to the purge path affect emissions. The purge control solenoid normally routes fuel vapors from the charcoal canister into the intake to be burned. If that solenoid has been bypassed, that control is no longer functioning as designed, so the EVAP system is effectively modified. In that modified state, vapors aren’t being purged and burned the same way, which tends to push more unburned hydrocarbons into the exhaust and can also affect the air-fuel balance enough to raise carbon monoxide.

So, you should record the EVAP testing data as modified, knowing that the bypass will drive higher HC and CO readings than in the original, properly functioning system. Entering it as original would misrepresent the system’s behavior under test, and saying no data would be recorded would ignore the observable emissions changes caused by the bypass.