1998 Forester 5MT 16X,XXX miles or so.

 

Reoccurring DTC PO440.

 

Items replaced:

Gas cap

Pressure Control Valve

Charcoal canister

 

Items known to be working:

Drain valve

Purge Control Valve

 

Using SSM II Fuel tank pressure will max out at .225"Hg with the car idling and warm.

 

If I take a rubber stopper and plug the metal pipe that terminates in the frame rail, the system will eventually build up to almost 1.0"Hg.

 

Shouldn't the pressure control valve try to reduce this when pressure gets to high? Other cars inspected fluctuate between .250-.500"Hg while idling. Pressure slowly builds, PCV switches on for a second or two, pressure dumps out quickly, then a slow build again.

 

I have read, and re-read the TM for this, and don't have any information on what pressures should be seen where, when, and for how long. The code is for a leak, I do not believe there is a leak in the system, as I can plug the only open hole (after the drain/filter in frame rail) and it builds and holds pressure. (well, slowly bleeds off in about 5 minutes when you turn the car off)

 

Do I dare say I need to look into the vent valve on the tank? zzz

 

Roll valve? Shut valve?

 

For what ever reason, I can't wrap my head around this issue...

 

Thanks!

LJ

When you find the solution, let us know. I'm fighting with this myself.