charcoal canister leaking raw fuel

[chp56]

canister seems to be full of fuel, and leaking out of one of the hose connections-isnt it only supposed to contain vapors?

[FJCamper]

Hi Chp56,

The charcoal cannister is just part of the "evaporative emission control system." It's supposed to trap evaporating fuel from the gas tank and via some clever low pressure/high pressure plumbing, suck the vapor to the cannister.

I would imagine you have raw fuel being sucked to your cannister when you get surges of fuel on a full tank because the evap control system plumbing is not working somewhere in the circuit.

I remember late one quiet night hearing one of these malfunctioning systems slowly equalizing pressure ... it sounded like breathing, which was spooky. Back in the day, out of warranty cars had these systems stripped out, and all hoses plugged. The old cannisters had slowly become napalm bombs in waiting.

FJC

[chp56]

Thanks FJC-
As a matter of fact it WAS when I topped it off-I think I'll just dispense with the system altogether anyway (74 Super)

[Piledriver]

Actually you would be FAR better off fixing it, unless you like your car//garage smelling of old gas station.

Evap systems on older cars are simple and relatively bulletproof.
They only give trouble when not maintained.
(disconnected//plugged lines/rotted hoses)

Even newer cars evap systems work exactly the same way, but they get a bad rep due to all the mandated OBD/OBD2 "self test" features that in practice are more likely to fail and can drive people nuts.

The large plastic "manifold" that runs across the top of the SB trunk ...its purpose in life is in fact to trap liquid fuel, and allow it to drain back into the tank. On some vehicles there is also a front tank under the DS front fender that traps liquid fuel to keep it out of the charcoal. (the high mount over-trunk setup works FAR better as a fuel/vapor separator IMHO, the under fender setup has no way to return liquid fuel to tank)

The rear tank is purged by fresh air sucked into the engine, and actually contains charcoal.

It's possible (likely even) that someone hooked something up wrong at some point, resulting in liquid in the tank.

If things are working as designed it should deal with it automagically.

You may just need a hose clamp.

[misterman]

If its dripping fuel, prob too full. If its leaking, mine was too. Come to find out it was the fill neck's vent line (1/2)in rubber hose.
I removed all mine. The thing under ur "hood" in the trunk is actually the vapor expansion tank. Used to catch vaopr and recondense it and use the liquid to not waste gas to evaporation. The charcol can is in the passenger rear fender and only catches one tiny plastic blue hardline vent.
Charcol can powered by engine fan and spend via air cleaner port.

Try fulln it up with 2 gal and see if u smell gas. Then we go from there. Full tank and smell gas = 10,000 possibilities.

[Piledriver]

Right, but if the purge setup (either vacuum or fan fed) for the tank isn't hooked up, it will eventually fill up.

First step: replace can. All modern cars have one, the junkyards are full of probably perfectly good candidates.
(there is also the perfectly functional DIY Petco/Home depot design discussed previously, but it will eventually rust out, modern ones are ~always plastic, and almost free used)

The "over the top" tube also should be acting as a vapor/liquid separator, returning liquid fuel to the tank.

The ~only thing hitting the charcoal should be vapor, not liquid.

Modern vehicles use engine vacuum off idle to simply suck air through the canister.
The vacuum advance port is probably a good control signal.

[Steve Arndt]

the junkyards are full of probably perfectly good candidates.

Like.

s

[Piledriver]

[misterman]

Right, but if the purge setup (either vacuum or fan fed) for the tank isn't hooked up, it will eventually fill up.

yes, unless say, the charchol can and expan tank "felloff" and left the straight dump ouside the vehicle...

But that wouldent comply with smog of corse

[Piledriver]

True, the early VWs just dumped under the front apron behind the spare...
But it does eliminate hat "old gas station" smell.

Easy to fix (or even add on), and doesn't hurt performance one iota.

[Steve Arndt]

Yet another problem with my individual throttle bodies, no way to vacuum out the canister easily.
Since my tail pipe is zero emissions (almost) I need to tighten up the evap. We have a junker late 80s Suzuki suv in the back lot, I think I will search it for activated carbon canisters. I already scored some very nice little surface mounted dome light assemblies out of it

[Piledriver]

Yet another problem with my individual throttle bodies, no way to vacuum out the canister easily.
Since my tail pipe is zero emissions (almost) I need to tighten up the evap. We have a junker late 80s Suzuki suv in the back lot, I think I will search it for activated carbon canisters. I already scored some very nice little surface mounted dome light assemblies out of it

No problem, you have an effective case evac setup, I wouldn't hesitate to use that as the purge flow through your case... Have you measured the vacuum level yet at various loads?