Location of EVAP vent to atmosphere--'98 Contour

ford
contour

#1

Okay, I had a OBDII code of P0446 about a year ago that resolved itself. Well, it’s back on now. Since the code came up initially while riding dirt roads, my suspicion is a clogged vent to atmosphere.



However, I’ve unscrewed the charcoal cannister from under the fuel tank, and no vent here…just multiple tubes leading away.



Any idea where the vent’s located? Apparenly the solenoid is on the firewall: vent also?


#2

year, make, model please…


#3

The idea behind an evaporative emissions system is that there is not supposed to be a vent to the atmosphere because emissions from gasoline are just as polluting to the atmosphere as exhaust fumes are. If your evap system does vent to the atmosphere, then something is wrong.


#4

The OP clearly indicated a 1998 Ford Contour.


#5

That’s not entirely true. For safety reasons, the tank is allowed to vent straight to atmosphere (usually via the gas cap) if pressure in the tank becomes excessive.


#6

That code indicates a malfunction of the EVAP system vent control. However, that vent, if it’s the one I’m thinking of, is designed to allow air into the fuel system to prevent excessive vacuum from building the the event of an obstruction in the intake path for the tank. That path comes through the charcoal bed in allows air in as the gas drops. If that path is obstructed sufficient to allow that vent to activate, the differential pressure sensor (vacuum sensor) in your tank will trigger a fault code. I’m not positive, but I believe that same sensor may also trigger the vent itself.

Mu neighbor’s pickup had one of these go bad. In his vehicle it was in the line, somwhere just in front of the tank.

I’d suggest you get a good manual, and if it isn;t in the manual do what I do…stop by the parts counter and politely ask them to look it up and print you an “exploded view” drawing of it’s installation.


#7

This has to do with the vent control valve for the EVAP system.

The carbon canister collects fuel vapors and stores them. When the engine is started cold, this vent control valve opens and allows these fuel vapors to be drawn into the engine to be burned. So there’s a problem with this vent control valve, be it mechanical or electrical.

Tester


#8

“For safety reasons, the tank is allowed to vent straight to atmosphere (usually via the gas cap) if pressure in the tank becomes excessive.”

Ummm…Since this is not how the evap system normally works, and since you are describing a situation of excessive pressure build-up in the tank, I will repeat my earlier statement that, “If your evap system does vent to the atmosphere, then something is wrong”. Surely you can’t think that this type of situation is normal.

And, to go back to the OP’s original question, I interpret the question to mean that the OP believes that the evap system normally vents to the atmosphere. If I am correct in my assumption, then the OP was mistaken about how the evap system normally functions, and that is what led to my response.


#9

Is Ford using “vent” to describe the purge valve & solenoid?

I show the purge valve as being codes 0443 through 0445 and the vent control system being 0446 through 0449. There exist both.


#10

Thanks for the help.

I fixed a bit of a kink in the hose that vents to atmosphere, and I cleaned a fair amount of dust out of the solenoid. The combination of these two actions solved the code.

The solenoid was on the firewall directly aft of the throttle body. It was almost impossible to see at first, but real easy to access once the resonator was removed!


#11

Fair enough…


#12

Thanks for the feedback. I’m glad the problem is solved.