Purge Valve

Replaced my canister purge valve today as I found the normally closed valve was leaking internally (if only slightly) between the canister hose and intake hose connections. The new valve was tested and held vacuum. No DTC was tripped and I found the leak because I was trying to trace negative fuel trims (rich run) at idle.

The leak meant it continuously drew fuel vapors through the canister into the intake. This added fuel at idle and would have reduced my fuel mileage, and possibly I guess, shorten the life of the canister.

I attempted to figure out how the valve works, but all I could determine was there is a rubber check valve attached to a large internal diaphragm, and the leak was at this check valve. This is a very complicated valve. My FSM uses a special scan tool connected to its test port to diagnose the system.

The valve is a plastic three port with two ports connected to the intake vacuum and one port to the canister hose. The canister hose (discontinued by Ford) has a plastic quick disconnect and internal o-ring that supposed to seal on the metal tube to the canister. It would be very difficult to test the integrity of the o-ring seal. If this connection leaks then your only choice is to clamp aftermarket vacuum hose to the metal tube.

The smallest port, which sees intake vacuum, does not hold vacuum. All I could determine is this port is actuated with the solenoid and opens and closes the check valve by the PCM by moving the diaphragm. This port also connects to ambient air with a foam filter, yet does not induce a vacuum leak into the intake. It's possible the filter could get plugged eventually.

I could not get any reaction from the valve when I connected a power source to the electrical connector, but the resistance was normal.

As normal maintenance I would suggest testing the valve for it's ability to hold vacuum on the two large ports. At only 80K this valve failed at pretty low mileage.

Picture: http://images.oreillyauto.com/parts/img/large/bwd/cp613photoprimary.jpg

Very interesting findings. 80,000 miles may be kind of low, but it's had 12 years of being exposed to fuel vapor too, which can't be easy on components.

I hope the replacement helps bring your FE back up to the levels you'd been seeing.

I recently (yesterday, actually) did the purge valve on mine, the valve was maybe 6 mo. old. In my case, same issue as described, slightly stuck open and a 2MPG drop in FE (although the topper I put on recently may be part of it too). In my case it really was a premature failure (good thing autozone honored the warranty).

So yeah, these can just stick up. Better than the one that I had when I bought the truck; the PO ran it w/o a filter and as a result the IAC and purge valve both had bug cocoons inside (the former I happened to have a JY replacement in the parts the PO included). Hence why I replaced it in the first place.