As described in a previous post (Oct 3rd 2009) I had a full tank of
gas and was told by another driver that gasoline was leaking out
onto the tire when taking a highway offramp (turning to the
right).
Per suggestions in my original post, I have removed all the
internal panels and the large plate covering the gas tank and
examined the hoses and various connections. Pictures are shown at
There is no apparent internal leaking, no stains or any sign of
liquid spilling or flowing around the tank or filler neck
cavities. The rubber filler neck is not brittle and appears to be
in good shape, as is what I believe to be the overflow tube (there
is a small spot of rust near the tube, but this doesn’t appear to
be a problem).
I’m guessing at this point that the hoses and everything leading
from the filler spout to the tank are good. There is a small hole
in the body near the fuel filler cap, and if the filler cap main
spring and/or seal and retainer assembly (AEU 1466 and AEU 4174
respectively, from JHM1176 parts manual) are bad they would allow
fuel to leak from the tank into the cavity and out the small hole
onto the tire.
So I’m going to replace the above-mentioned parts (or the entire
filler cap assembly if necessary), but does this seem to be the
likely culprit, or have I overlooked something else?
As always, thanks fr your assistance.–
jaguarbarney
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In reply to a message from jaguarbarney sent Tue 29 Dec 2009:
I doubt this is your issue, but I’ll throw it out there:
On my xjs, if I fill the tank to the tippy top, and then park the
car on about a five degree angle (with the left [gas cap] side of
the car lower than the right), then gasoline will leak out of tank.
No problem with the tank or anything, just leaks out of the same
hole through which you put gas into the tank. I guess the gas cap
isn’t tight enough.–
AG555
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In reply to a message from AG555 sent Tue 29 Dec 2009:
We may have the same problem. The parts I mentioned are the spring
and seal/gasket assembly on the filler cap. If they’re not making
a proper seal, maybe gas will leak out. I’m going to replace the
parts, and see if that solves my problem, will try parking at an
angle first, that sounds safer.
What year and model is your car?–
The original message included these comments:
I doubt this is your issue, but I’ll throw it out there:
No problem with the tank or anything, just leaks out of the same
hole through which you put gas into the tank. I guess the gas cap
isn’t tight enough.
The cap shouldn’t be leaking. After all, if it leaks liquid under conditions
you describe it will leak vapors which is an emissions problem. But, it
might be Barney’s problem. May both of you should have your caps tested.
I doubt this is your issue, but I’ll throw it out there:
On my xjs, if I fill the tank to the tippy top, and then park the
car on about a five degree angle (with the left [gas cap] side of
the car lower than the right), then gasoline will leak out of tank.
No problem with the tank or anything, just leaks out of the same
hole through which you put gas into the tank. I guess the gas cap
isn’t tight enough.
The coupe overflow drain hole is connected to a hose leading through the
boot and thence down through the boot floor behind the wheel to the roadway.
I’m not familiar with the convertible, but the first thing I’d do is to run
a wire through the drain hole and find out where it goes and if the hose is
good. It also occurs to me that the observer may have been wrong in saying
it was leaking onto the tire. Perhaps it was leaking behind the tire and his
point of view made it seem it was onto the tire.
I would also check the gas cap, or better yet have an emissions repair shop
test it. It should not be leaking gasoline. The drain hole is intended to
catch spillage while filling, and perhaps rain water.
I have a complete write-up on boot fuel odors, but doesn’t cover the
convertible.
As described in a previous post (Oct 3rd 2009) I had a full tank of
gas and was told by another driver that gasoline was leaking out
onto the tire when taking a highway offramp (turning to the
right).
There is a small hole
in the body near the fuel filler cap, and if the filler cap main
spring and/or seal and retainer assembly (AEU 1466 and AEU 4174
respectively, from JHM1176 parts manual) are bad they would allow
fuel to leak from the tank into the cavity and out the small hole
onto the tire.
So I’m going to replace the above-mentioned parts (or the entire
filler cap assembly if necessary), but does this seem to be the
likely culprit, or have I overlooked something else?
In reply to a message from Ed Sowell sent Tue 29 Dec 2009:
Mine is an 87. My solution was to just not park at an angle if I
fill it to the tippy top (it has to be filled to the very top for
this to happen). If you want to test this, just fill your tank to
the very top, then find an incline (left lower than right, not back
lower than front, for some reason the latter causes no problem for
me), park and see if gasoline slowly leaks out.
Ed, you think vapors leaking out of the gas tank can be an
emissions problem? What do you mean by that?–
AG555
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In reply to a message from AG555 sent Tue 29 Dec 2009:
The hole in the recess around the filler cap has a 1/2 inch rubber
drain tube that runs down and through a hole in the bottom of the
car to dump any spillage while filling the car.If you remove the
carpet piece on the left side you will see the hose just pull it
off of the metal nipple at the hole and blow air through it to
clean it and put it back.I would say that was the culprit, but
their is one more place that it could have been,but would not leake
due to a full tank.This other place is the fuel feed line under the
car it loops over the left wheel/Hub and turns up and into the
trunk floor to the tank line on the left side.Their is also this
same setup on the right side that is the return line back to the
engine it also runs down through the floor under battery and loops
over the wheel on the right side.These two lines are metal except
for a small section right over the half shaft axles and there the
line is a rubber section about 8 inches long that are prone to
leaking from exhaust heat, age, dry rot etc.Their is a section on
how to repair them with new sections of injection hose in Kirby’s
XJS book if this indeed is the problem but I would almost bet its
the drain tube that was just dumping the spillage as it is designed
to do.–
T Boy
Raleigh NC, United States
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The fuel filler cap on the tank neck is supposed to seal to the top of
the neck so that no vapor can escape from the tank when the car sits in
the sun and vapor pressure increases over the liquid fuel in the tank.
This is to meet federal emissions requirements. The vapor goes from
the tank through a tube to the charcoal canister located in front of
the left front wheel.
As part of the required emissions testing, many/most states state that
the inspector is to test the fuel filler cap on a device that
determines that the rubber seal inside the cap does NOT leak or lose
pressure/vacuum. The cap can be tested on such a device. Of course
you can simply examine the rubber seal inside the cap for cracking or
other failure which will cause it NOT to seal tightly to the top rim of
the filler tube. If the cap seal doesn’t leak vapor, then it won’t
leak liquid that sloshes against the cap at the filler tube when the
tank is full.
George Balthrop, Clifton, VA USA
89 and 85 XJ-S Coupes; 89 XJ40 VDP-----Original Message-----
From: AG555 alireza_g@hotmail.com
Ed, you think vapors leaking out of the gas tank can be an
emissions problem? What do you mean by that?
In reply to a message from T Boy sent Tue 29 Dec 2009:
I will check the tube tomorrow morning, and will look into
replacing the gasket / seal on the filler cap (it can’t hurt to do
this). I guess the only test after that is to top off the tank and
take her out, although dry salt-free days are few and far between
in New England this time of year.
Thanks all for the advice, I’ll update once parts have been
examined and replaced.–
The original message included these comments:
XJS book if this indeed is the problem but I would almost bet its
the drain tube that was just dumping the spillage as it is designed
to do.
I mean that the tank is supposed to be air/vapor tight, required since the
early 80s to control air pollution. There is a venting system that routes
vapors up front to the carbon canister under the left front wing, with an
elaborate system for purging the canister etc. All of that is wasted if the
filler cap is leaking. My point in bring this up was just to point out that
from what you said the cap is indeed leaking when it shouldn’t be. IOW, it
is not, or shouldn’t be, a vented cap. You can fix your leak on inclines as
well as strike a blow for clean air by replacing the cap. Or so it seems to
me.
In reply to a message from Ed Sowell sent Tue 29 Dec 2009:
Sorry but I have to mention that filling the tank to the ‘‘tippy
top’’ is a big no no the fuel needs room to expand when it warms up.
If you take up all the air space in the tank there is no room for
vapor so when you fix the leaking cap then the fuel (raw) will be
pushed into the carbon canister and probably leak out the front
instead. This is worse for new cars with press sensors in the tank
that ck for vapor leaks.
Nick
fuel vapor is unburned fuel = hydrocarbons= emissions problem–
The original message included these comments:
I mean that the tank is supposed to be air/vapor tight, required since the
early 80s to control air pollution. There is a venting system that routes
vapors up front to the carbon canister under the left front wing, with an
elaborate system for purging the canister etc. All of that is wasted if the
filler cap is leaking. My point in bring this up was just to point out that
Ed, you think vapors leaking out of the gas tank can be an
emissions problem? What do you mean by that?
That would be true if it were possible to completely fill the tank. I’ve
never seen the inside of the tank, but my guess is there is a small but
non-zero unvented ullage in the tank afforded by the placement of the vent
ports. Take a look at the photos of the tank in my write-up on fuel odors in
the boot to see where these vent ports are to see what I mean. The expansion
of liquid is very small, so just a fraction of an inch of unvented space at
the top would be enough to absorb liquid expansion. Also, there is a vent
tube in the neck itself, leading to the ullage space. IOW, I doubt the
scenario you describe is possible. This is not to say one should continue
triggering the pump nozzle after it clicks off, the risk being spillage at
the filling station.
Sorry but I have to mention that filling the tank to the ‘‘tippy
top’’ is a big no no the fuel needs room to expand when it warms up.
If you take up all the air space in the tank there is no room for
vapor so when you fix the leaking cap then the fuel (raw) will be
pushed into the carbon canister and probably leak out the front
instead. This is worse for new cars with press sensors in the tank
that ck for vapor leaks.
Nick
fuel vapor is unburned fuel = hydrocarbons= emissions problem
In reply to a message from konrads sent Wed 30 Dec 2009:
thanks, good to know–
The original message included these comments:
Sorry but I have to mention that filling the tank to the ‘‘tippy
top’’ is a big no no the fuel needs room to expand when it warms up.
If you take up all the air space in the tank there is no room for
vapor so when you fix the leaking cap then the fuel (raw) will be
In reply to a message from jaguarbarney sent Tue 29 Dec 2009:
My wife had to borrow the car one day and she was nice enough to
add fuel while doiing her errands. She put the gas cap on crooked
and before I knew it I had dranined the tank half way. I guess I
made lots of fast right turns.–
The original message included these comments:
I have a 1995 XJS 6.0 liter convertible.
onto the tire when taking a highway offramp (turning to the