Gas tanks overheating problem
 

Please help,I'm traveling from WI to texas in my new to me 1985 XJ6, I am having trouble with my internet connection so I can't really serch much.
The problem I am having is that the fuel in the tanks is overheating really bad,to the point where the gas starts boiling, any ideas?

What makes you think the gas is boiling?

What exactly is happening?


Cheers
DD

When I open the caps to fill it up I can feel the heath comin out and hear the bubbling

Is the air conditioning working? The car has a fuel cooler that operates off of the air conditioning system.

Gasoline boils at anywhere between about 190ºF and 400ºF (depending on a slew of variables). I can't think of any way it could ever get that hot unless, perhaps, the fuel pipes were touching the exhaust pipes or such.

Is the heating shielding in place on the body in the tunnels where the rear mufflers are? That's right next to the fuel tanks



Cheers
DD

maybe what you are perceiving is a "whooossshhh" of fuel vapors coming out of the tank or tanks?

If it's been quite hot where you are lately it's probably not so much boiling as generating a lot of vapor, so when you open the gas cap you hear much gurgling as the vapors rush to escape. You could even get some splashing of droplets of fuel from this without it actually indicating a problem.

-mB

sou nds similar to the issue I had a few months ago. I diconnected that valve under the passenger tire fender and it stopped. it wasn't venting and was causing the fuel to build up pressure causing the hiss and whoosh

Yes, this seems to be the issue, I am driving with the fuel caps opened, I will do a follow up once I get to my computer, so far made it from Milwaukee, WI to Laredo, TX with no issues

look under the fender at the passenger tire, under the head light area. You'll see the evap canister and some hoses connected to a tee, disconnect the big hose from the tee. Thats what fixed my issue.

it is better to defeat the one-way plastic valve near the charcoal canister which is the cause of the vapor build-up. Do not leave any hose disconnected otherwise you will start to smell gasoline. The valve is called "Pressure relief Valve", a GM part which does not relieve the pressure.

the valve looks like the picture below. One port is larger than the other so it can only be installed one-way. Raise the front passenger side of the car, look behind the tire towards the front, look at the inner wall and you will see a metal line connected to a rubber hose held by a clip on the wall, after that you will see the valve.

remove the valve, find a 1/8" drill bit and push it through it, pulling it the opposite side, this will eliminate the vapor build-up permanently, then reinstall the valve.

my 1984 has been like that since 1991, no issues, no fuel smells, no vapor build-up.

Thanks Jose! I forgot to drill the hole and lately been wondering where the fuel smell was coming from. You just explained it and reminded me to drill the hole.:icon_doh:

you're welcome amaezing,

that vapor buildup in the tanks has been a problem with the Series 3 XJ since the beginning, I learned the trick from a factory-trained mechanic who told me the valve is not correctly calibrated so it doesn't open when it should, to allow fuel vapor to move into the charcoal canister and then to the engine where it is burned.

you don't need the valve at all, just connect both hose sections with a plastic connector, the kind that you can connect different-sized hoses, sold at autoparts. I eliminated the valve in mine, though the drill bit trick does the same thing.

what you don't want to do, is to leave the vapor system "open to atmosphere", because then you are inhaling fuel vapor (the fuel smell).

That makes sense. I'm just gonna eliminate it altogether now. easier than draggin out the drill and the bits......etc.....

As you've read, the issue is not fuel boiling or any sort of overheating. The car is safe to drive as-is. No need to leave the caps open.

Thanks guys, the Jag ran like a champ during this 2,000 miles, now I will look into venting the tanks, I will be drilling the valve for sure.

Thanks again and I am sure I will have many questions for you guys in the future.

Glad to hear you made it. I have found this forum is one of the best i've ever been on.

guys,
if you want to save the valve, (even though it is useless anyway), you can buy a splicer for two different sized hoses at Autozone, Advance auto, O'Reilly's , like the one below:

Deleted... posted reply to wrong thread