Two weeks ago, I filled up both tanks and took a 180 mile trip with my XJ6. Going, I used the left tank and on the return trip, I switched to the right tank.
Halfway back I started to get a slight misfire or should I say an occasional RPM drop while driving at 80 mph.
When I got home and parked, I heard this gurgling sound from the tank. I opened the left tank and there was a very small (normal?) vent escape. Nothing to worry about there.
Opening the right tank there was this giant whooosh and the tank continued venting for about 20 seconds before it completely stopped.
This is the first time this has happened in 5 years of me driving this car.
Why would it build pressure in the right tank and not the left? I thought that the venting was common to both tanks.
I have not driven the car since.
What should I check first and how do I go about preventing this from happening again?

 

Hi

I have the EXACT same situation but mine is left tank. The venting is common at some point heading fwd to the evap chatcoal cannister in front fender...

...but each tank has its own private run of piping leading to that common T. That crazy piping goes up into to C pillar on each side of rear window and back down, etc

I wish I had a solution. I leave my left gas cap open so my tank is not imploded. Some suggested debris has clogged my left venting run and perhaps disconnecting pipe/hose in front by evap cannister and gently blowing compressed air back toward tanks might help

Figuring this out on my list but pretty far down unfortunately. Share any fix you discover

Randy

 

From memory...and not a very clear one....the common T is just above the rear suspension cage, RH side.

Cheers
DD

 

Hi, don't have any pictures handy but going from memory, the filler neck has a very small hole on the forward side that goes to the tube the vent hose connects to. I cleaned mine with a used guitar string, but I think I also have seen a cleaning brush set at harbor for small carbs that would work. The clog might be elsewhere but could hurt to start with the easy fix !

Cheers,
Brian

 

Brian is correct.

Arrow points to small vent hole in the filler neck.


Arrow points to the vent hose, at the forward end of the cap, that disappears into the fender to the vapor recovery system.

This is a poor photo but best I could do.
It will give you the idea anyway.
(';')

 

I do with my XJS had those lovely chrome filler caps!

 

Some pictures and diagrams for you. A small air pump for a bicycle tire and a rubber valve stem from a automotive wheel cut down for a test hose. with a low fuel tank, remove fitting from half way up the tank. Install test pipe and have the gas cap open. Start air pump and you should be able to hear, feel air pressure at vent hole under hinge of fuel cap. If not you have blockage in vapor separator. Check for blockage at vent hole as Kudzu suggested.
Remove hose under edge of rear windscreen in trunk. pressure test again from first test site. And so on until you find the place of your blockage. I look at this drawing from time to time and wonder if the side with the blockage could be bypassed to the good side with some vacuum hose and small T fittings.
Thank you.

Larry Louton

 

Larry -

Getting back to this issue before summer hot sun causes this to be a real issue.

Awesome debug description and pix

Thanks!

Randy

 

Not pressure. but vacum. A vent issue.

 

Not sure what yoy mean but the problem I think goes both ways... Vacuum implosionn if driving and fuel level falling, but I also have the issue with the car just sitting in the sun. I believe this is expansion due to heat.

Either way, gotta fix it!!!