What causes fuel to leak out of this hose that I assume should only have fumes coming out of it. This leads into the charcoal canister to be "cleaned"? I only noticed this as the two sections of hose were not connected and when I pulled into my parking spot at work, I could smell a strong odor of fuel.

The ENTIRE fuel system has been replaced with new except the hard lines.
31,000 miles.

 

That's not a leak MSG, that's a malfunction. Not supposed to be raw fuel in the evap lines but it invariably gets there (and is dangerous) when the tanks overfill and over pressure and send fuel into the evap lines. You say everything was replaced, did you replace tanks too? Look for stuck tank selector valve and/or return valve.

 

Yes, everything is new including 2 new tanks, two new changeover valves or whatever they are called. The 2 in the rear trunk and the 2 in the rear wheel wells are new. New fuel pump, 2 pre filters before the fuel pump, new injectors and all new lines.

Is it pressure from the tank not venting that "forces" fuel to go where only vapors should go? If so, what do I look at to fix so the system can vent properly? This only happened on the driver's side tank and not the passenger's if that matters. And yes, I heard the "whoosh" when I opened the driver's side filler cap.

 

did you replace the electronic Purge Valve located under the air filter area?

 

Uhm, no... Could that be causing my issue? I ran it for probably 5 miles tonight of the driver's side tank and no leak. Or does it take a while to pressurize the tank?

I will look into the purge valve.

 

If I don't have emissions to worry about and the leaking fuel is caused by excessive pressure in the tank, can the tanks be vented to atmosphere, so the pressure doesn't have a chance to build up?

The only issue this car has ever given me is fuel issues.

 

remove the black plastic check valve shown in your photo under the yellow circle, (lower vapor line).
**this check valve is normally in the top fuel vapor line between two different diameter hoses, then from the check valve the hose connects to the carbon canister. From the carbon canister another hose enters the engine compartment and connects to the Purge Valve, then the purge valve connects to the intake manifold.

Another option is to push a drill bit through the check valve to tear the inner membrane of the check valve.
The check valve is supposed to open at a given pressure to allow fuel vapors to travel to carbon canister, then to the electronic purge valve to be burnt at the engine's intake, but it doesn't open creating the "wooossshh" pressure release at the tanks when the fuel cap is opened.

This plastic check valve came from General Motors, it is not calibrated for the XJ-6 / 12.

Tearing the inner membrane of the black plastic check valve has the same effect as "system open to atmosphere", while keeping the system closed to stop fuel odor.

The purge valve may be stuck closed or clogged, not opening to release vapors. Test it outside of engine, or replace it if it doesn't "click" open/close.

 

MSG, I know it's a real pain in the butt, but when you get it sorted with everything new like this it'll prob be good for many years. What Jose said, and/or you could still have a faulty changeover valve, or could have even got two of the same side return valves, one is normally open the other is normally closed. Gonna have to verify that the dash switch is switching voltage properly to the changeover valve and to the correct return valve, and that the valve is in the correct state for that side. I've seen new valves contaminated by residual fuel left in lines and maybe fpr/injectors. Sometimes all it takes is one lousy piece of trash to stop a new changeover valve from closing completely etc... Even if you vent to the atmosphere directly, if a valve sticks you can still get fuel out the vent hose onto the ground, it's just a much shorter, less complicated path and the fuel isn't potentially running through vapor lines in the cabin. And yes, this to me is one of the most aggravating, common and dangerous issues with these cars, I would always factor this operation into the cost of purchasing any future vintage XJ.

Ps... I think this was prob the third time I asked if you'd replaced the tanks, a little embarrassing, I'm only 66 but sometimes my mind feels much older.

 

What is frustrating is all was good for several months after everything was renewed. Switching between tanks worked, no leaking fuel, no fuel tank issues and then all of a sudden it started leaking again. The hose had previously been disconnected after replacing the charcoal in the evap. cannister. No question any small bit of debris could cause and issue and one of the reasons I added 2 pre filters to help prevent debris from getting into the switchover valve, the one in the truck.

So, to clarify, the one way valve is intalled incorrectly?

 

in my 1984 XJ6, the plastic check valve is installed between the top hoses. The picture of your car shows the valve at the bottom hoses.

The plastic check valve has two ports, one is larger diameter than the other, and the two hoses match each port, one hose is larger than the other, so there is no way to install it the wrong way.

To answer your question: I don't know. if your car is newer maybe the hoses' position was changed.

 

MSG, if it was all running well for that period of time I doubt anything is installed incorrectly, I suspect either the dash switch is malfunctioning and not switching the changeover or returns correctly, or an electrical valve isn't working properly. If it's consistently malfunctioning, you can check that fuel is returning into the correct tank while idling by looking into the filler with a light. If yes then I would suspect the changeover valve. I had two new changeover valves that would not close completely, so were pulling fuel from both tanks at the same time but returning to only one tank, it took a little longer but would eventually overflow.