2000 225 explorer fuel vent

[johndl58]

I searched to try and figure this out but to no avail.
I believe I'm having a vent issue. The pressure practically blows the fill cap out of my hands I'd left awhile without removing it.
It seems the vent is clear all the way through. I've removed the line from the tank and blown air through it no problem. I've also blown air into the tank through the built in barb. The vent line goes to the filler neck and has a small port that opens into the filler. When the cap is on, there is absolutely no way this can vent to the outside. The cap is a metal cap with a rubber seal that seals off the opening from the very top. What am I missing here? How does this tank vent, or rather, supposed to vent? Thanks for any insight.

[johndl58]

[johndl58]

Those are pics I took of the cap/fill. The key is pointing at where the vent opening is located.

[RickK]

You said you blew the hose out, did that include through the part that the key is pointing to? If so, maybe it's time for a new cap. Maybe it's not passing fumes?

[johndl58]

I did blow air through it. No problem. What I don't understand is how the air actually gets out. The cap is solid metal with no vent holes. 

[Capt. Bob]

That appears to be a Perko vented cap. It functions by slightly raising the cap above the fill neck to release the pressure. I would think that Rick is correct in suggesting to replace the cap.

It appears to be this model: Perko 0540DPG99A Vented Fuel Fills - Gas Cap, O-Ring and Retainer

Good luck.

[johndl58]

Thank you for that explanation as to how this system vents. One more question, how does it introduce air into the system?

[Capt. Bob]

I'm not sure that the cap is a "perfect" seal such as a non-vented cap. The "valve" within the cap itself works in both directions, either pressure buildup within the tank or a vacuum buildup while underway. In either case, the "valve" will allow air to escape or enter, I'm thinking around its edge where the outer gasket meets the cap itself. It appears this older design (pre 2011) would allow water that was standing around the cap to enter the fuel supply. Perko sells a spacer that raises the cap slightly above the deck to allow water to pass underneath and not get drawn into the tank while venting.

Again, it appears your cap has met its maker and no longer releases/draws air. In visiting the Perko site, the replacements seem somewhat expensive.

[johndl58]

Thanks for the explanation. I found the whole assembly for like $50 on Amazon, meanwhile they also have just the cap for $68. Go figure. I'll definitely look for that spacer you mentioned as well.

[johndl58]

Just an update/fyi. I looked into the cap again today. Underneath the gasket are some little holes where the air is supposed to vent out of. If I leave the cap loose, the vents work as designed. If I cinch down the cap, the gasket seals off the the little holes preventing the cap from working properly. I'm not sure the cap is faulty. It's not designed to "pop up" like was suggested. Maybe the gasket isn't supposed to be there? I'm pretty confused by the design of this thing.

[Scode68]

Just wondering if you figured out the operation of this cap.  My 2001 215 Sport has a similar one and I'm thinking its not working or maybe I'm overtightening it.  On a day in the the 80s (or warmer) my carbs will weap fuel and drip om the ground.