Canister purge valve constantly opening

Question

I have a 2008 Hyundai Santa Fe GLS, 2.7 L V6, 2WD, 5-speed manual, 113,000 miles.

I recently replaced the Canister Purge Valve, because the solenoid was burned up and check engine light was on for that code. I noticed when I was replacing it that it must have been replaced once before because it was not the OEM part (my new one is the OEM part.)

The purge valve has not worked for probably 20,000 miles.

Problem: Since installation, while the engine is running, I hear the purge valve start opening in rapid succession (5 times a second) for about 2 minutes, then a 30 second break, and repeating this all the time.

I don't know how the purge system determines when to open, how often to open, or how long it should take to relieve 20k miles of vapor storage.... but it seems like removing the valve should have released the vapor.

I've unplugged the solenoid for now, because that constant pumping seems like it would just burn the coil up again! Am I wrong for thinking something is wrong with the evap system? Or is this normal behavior?

Fred Wilson · Accepted Answer

The Purge is controlled by the PCM with a pulse width modulated switch signal. It is normal for it to cycle rapidly. This allows small amounts of the fuel vapor to be metered into the cylinders. This method allows the system maintain fuel control.

One of the main jobs of the evaporative control system purge valve is to maintain a slight negative pressure in the fuel tank so that fuel vapor is not pushed out thought the carbon canister and into the atmosphere.This flow direction draws fresh air through the activated charcoal in the carbon canister. This then removes the fuel from the carbon getting it ready to capture the outward flow that happens when the engine is off and during refueling.  So the purge will be on much of the time that the engine is running. It is usually turned off during deceleration and other times briefly to test mixture and run other tests. Fuel tank level has little affect on the amount of time the purge in on.

Gregory Scharf · Answer

Something i just learned is that if you have an electric gas peddle than if you ever reset the computer system you need to recalibrate the peddle. Super simple u just turn key to On but dont start the car wait for all the dash lights to go out. Ur electric warning light and or ur check engine light may still be on thats ok... slowly press peddle to the floor than slowly release the peddle all the way back out than turn ur key to off position than start your car give it a second and than your off to the races

Answered by Gregory Scharf on July 24, 2021

Canister purge valve constantly opening

2 Answers

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