[xj] Disappearing fuel

problem? Could it be possible that even though I can switch between the two
tanks, the car might be drawing through both tanks? I don’t smell fuel
anywhere around the car.

Could be that the switch is not working and that it is actually reading the level in the one tank only. Could also be that the changeover valve is stuck in the middle, allowing the car to drain off both tanks. Could be magic, too.

I know this topic has been brought up before, but from searching the
archives, I found no real solution.
I have a “disappearing fuel” problem where I put $20 in, filling up one tank
and then putting the remainder in the other tank, usually the other tank
ends up 3/4 full. I then set it on one tank, until 1/4 of the gas is left,
then switch over. However, the fuel gauge shows that the other tank is 1/4
full-the same amount as in the empty tank!
Is there anything I should check, or is this simply an electronics/gauge
problem? Could it be possible that even though I can switch between the two
tanks, the car might be drawing through both tanks? I don’t smell fuel
anywhere around the car.

Hi Paul and the rest of you all :slight_smile:

I have the SAME problem!! I have a Mobil speed pass so I always fill both
tanks up completely everytime I go to the gas station.

And I will only use the left or right tank, and when I’m about down to 1/2,
1/4 I switch over and the needle BARELY moves!

Is there ANY way to correct this! I don’t remember this happening when I
first got the car.

Paul you are not alone buddy
:slight_smile:

$teve

1986 Jaguar XJ6 Series 3 (11/85)
Black / Grey Leather
95,000 miles and goin’ strong!

Visit My Jag Homepage!
http://welcome.to/stevesjagsite.com

This could be contagious! Same with mine. New valves (all three), new
connectors, new sender in one tank, and a refurbished one in the other,
correct voltage gets to all three. Fuel return flow goes to the correct
tank. No smell of fuel anywhere - the car is garaged, so I’d easily
smell a leak. But, same symptoms; change tank from one that is down to
1/2 full or so to one that was previously full - and it reads the same
as the half-empty one. But only intermittently! If I am driving while
I use the half tank, then change over, the other tank reads full. If I
leave it a while, it reads the same as the one I have been using. I’d
speculate that the fuel from one tank is syphoning over into the partly
empty one, except that the level in the partly empty one doesn’t go up.
Damned baffling.

I guess it must be down to the switch - it is the only thing left in
circuit that hasn’t been changed or cleaned!

Craig> -----Original Message-----

From: owner-xj@jag-lovers.org
[mailto:owner-xj@jag-lovers.org]On Behalf
Of $teve
Sent: 30 November 1999 02:44
To: Paul; xj@jag-lovers.org
Subject: Re: [xj] Disappearing fuel

Hi Paul and the rest of you all :slight_smile:

I have the SAME problem!! I have a Mobil speed pass so I
always fill both
tanks up completely everytime I go to the gas station.

And I will only use the left or right tank, and when I’m
about down to 1/2,
1/4 I switch over and the needle BARELY moves!

Is there ANY way to correct this! I don’t remember this
happening when I
first got the car.

Paul you are not alone buddy
:slight_smile:

$teve

1986 Jaguar XJ6 Series 3 (11/85)
Black / Grey Leather
95,000 miles and goin’ strong!

Visit My Jag Homepage!
http://welcome.to/stevesjagsite.com

Hi folks!
I think these fuel systems have minds of their
own.
I fill both tanks and use the L tank first until
almost
empty. Then I switch to the R tank. When the R
tank
is almost empty I can switch it to the L tank and
it’s over
1/4 full. Yes, it is magic!!!

Robin----- Original Message -----
From: Paul paulbentz@home.com
To: xj@jag-lovers.org
Sent: Monday, November 29, 1999 7:30 PM
Subject: [xj] Disappearing fuel

I know this topic has been brought up before,
but from searching the
archives, I found no real solution.
I have a “disappearing fuel” problem where I put
$20 in, filling up one tank
and then putting the remainder in the other
tank, usually the other tank
ends up 3/4 full. I then set it on one tank,
until 1/4 of the gas is left,
then switch over. However, the fuel gauge shows
that the other tank is 1/4
full-the same amount as in the empty tank!
Is there anything I should check, or is this
simply an electronics/gauge
problem? Could it be possible that even though I
can switch between the two
tanks, the car might be drawing through both
tanks? I don’t smell fuel
anywhere around the car.

I know this will just irritate people to no end, but my gas tanks work
properly, on both cars. At my suggestion, my wife and son both begin with
the left tank, which I reason will offset the weight of the driver, then,
when nearly empty, they switch to the right. When that one’s almost empty,
we refill.

Each tank takes between 9.5 and 10.5 gallons to refill, and the gauge
indicates correctly based on how close to the “E” indicator it is.

I would theorize that those of you who are magically gaining or losing fuel
have a problem with the changeover valve. I bet it’s not completely shunting
the fuel flow and gasoline is seeping from one tank to the other when the
car sits, and/or the pump is drawing primarily from one tank, but pulling a
small amount from the other, too. By combining both options to various
degrees I think you could cover the “losing gas” and the “creating gas”
scenario.

“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – www.cableone.net/jcca----- Original Message -----
From: “Jeff & Robin Richards” richards@eagnet.com
To: “Paul” paulbentz@home.com; xj@jag-lovers.org
Sent: Tuesday, November 30, 1999 3:00 AM
Subject: Re: [xj] Disappearing fuel

Hi folks!
I think these fuel systems have minds of their
own.
I fill both tanks and use the L tank first until
almost
empty. Then I switch to the R tank. When the R
tank
is almost empty I can switch it to the L tank and
it’s over
1/4 full. Yes, it is magic!!!

Robin
----- Original Message -----
From: Paul paulbentz@home.com
To: xj@jag-lovers.org
Sent: Monday, November 29, 1999 7:30 PM
Subject: [xj] Disappearing fuel

I know this topic has been brought up before,
but from searching the
archives, I found no real solution.
I have a “disappearing fuel” problem where I put
$20 in, filling up one tank
and then putting the remainder in the other
tank, usually the other tank
ends up 3/4 full. I then set it on one tank,
until 1/4 of the gas is left,
then switch over. However, the fuel gauge shows
that the other tank is 1/4
full-the same amount as in the empty tank!
Is there anything I should check, or is this
simply an electronics/gauge
problem? Could it be possible that even though I
can switch between the two
tanks, the car might be drawing through both
tanks? I don’t smell fuel
anywhere around the car.

Paul: I had this exact problem when I purchased my 87 V12; that car had been
little used and I suspect that old fuel had left a varnish on everything. I
put Chevron TECHRON additive in both tanks, and with the advice of others on
the list, cleaned the connector of the changeover switch in the trunk,
cleaned the bullet connectors of the wheel well return switches (all of
these LOOKED clean, by the way), and the problem has disappeared. I am not
sure which area was the source of the problem, but I suspect it was the
changeover valve not closing completely.
Gregory----- Original Message -----
From: Paul paulbentz@home.com
To: xj@jag-lovers.org
Sent: Monday, November 29, 1999 4:30 PM
Subject: [xj] Disappearing fuel

I know this topic has been brought up before, but from searching the
archives, I found no real solution.
I have a “disappearing fuel” problem where I put $20 in, filling up one
tank
and then putting the remainder in the other tank, usually the other tank
ends up 3/4 full. I then set it on one tank, until 1/4 of the gas is left,
then switch over. However, the fuel gauge shows that the other tank is 1/4
full-the same amount as in the empty tank!
Is there anything I should check, or is this simply an electronics/gauge
problem? Could it be possible that even though I can switch between the
two
tanks, the car might be drawing through both tanks? I don’t smell fuel
anywhere around the car.

Mark, I think you are correct, but my spirit of competetiveness will not
allow me to be silent: I can beat you. I now have 3 SIII cars whose fuel
systems wok perfectly (2 of them always have worked perfectly!).
Gregory----- Original Message -----
From: Mark Stephenson marks@starlink.com
To: XJ Lovers xj@jag-lovers.org
Sent: Tuesday, November 30, 1999 9:10 AM
Subject: Re: [xj] Disappearing fuel

I know this will just irritate people to no end, but my gas tanks work
properly, on both cars. At my suggestion, my wife and son both begin with
the left tank, which I reason will offset the weight of the driver, then,
when nearly empty, they switch to the right. When that one’s almost empty,
we refill.

Each tank takes between 9.5 and 10.5 gallons to refill, and the gauge
indicates correctly based on how close to the “E” indicator it is.

I would theorize that those of you who are magically gaining or losing
fuel
have a problem with the changeover valve. I bet it’s not completely
shunting
the fuel flow and gasoline is seeping from one tank to the other when the
car sits, and/or the pump is drawing primarily from one tank, but pulling
a
small amount from the other, too. By combining both options to various
degrees I think you could cover the “losing gas” and the “creating gas”
scenario.

“Mark 1” Mark Stephenson
1952 XK120 Roadster #673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP
Jaguar Club of Central Arizona (USA) – www.cableone.net/jcca

----- Original Message -----
From: “Jeff & Robin Richards” richards@eagnet.com
To: “Paul” paulbentz@home.com; xj@jag-lovers.org
Sent: Tuesday, November 30, 1999 3:00 AM
Subject: Re: [xj] Disappearing fuel

Hi folks!
I think these fuel systems have minds of their
own.
I fill both tanks and use the L tank first until
almost
empty. Then I switch to the R tank. When the R
tank
is almost empty I can switch it to the L tank and
it’s over
1/4 full. Yes, it is magic!!!

Robin
----- Original Message -----
From: Paul paulbentz@home.com
To: xj@jag-lovers.org
Sent: Monday, November 29, 1999 7:30 PM
Subject: [xj] Disappearing fuel

I know this topic has been brought up before,
but from searching the
archives, I found no real solution.
I have a “disappearing fuel” problem where I put
$20 in, filling up one tank
and then putting the remainder in the other
tank, usually the other tank
ends up 3/4 full. I then set it on one tank,
until 1/4 of the gas is left,
then switch over. However, the fuel gauge shows
that the other tank is 1/4
full-the same amount as in the empty tank!
Is there anything I should check, or is this
simply an electronics/gauge
problem? Could it be possible that even though I
can switch between the two
tanks, the car might be drawing through both
tanks? I don’t smell fuel
anywhere around the car.

I would theorize that those of you who are magically gaining
or losing fuel
have a problem with the changeover valve. I bet it’s not
completely shunting
the fuel flow and gasoline is seeping from one tank to the
other when the
car sits, and/or the pump is drawing primarily from one tank,
but pulling a
small amount from the other, too.

OK for theory, Mark. So I pulled the C/O valve and checked it on the
bench; confusingly it seemed OK, but I replaced it anyway, plus the
bullet connectors. It hasn’t sorted the problem. Gas was returning to
the wrong tank, so I replaced both in-line valves. Fuel now drains to
the correct tank, but the problem of apparent vanishing fuel continues.
So we now have:

3 new valves
new in-line connectors
One new and one refurbed tank sender

Correct voltage levels getting to all three valves, and each one issues
a healthy click when acuated.

There is nothing original left in the system but the tank changeover
switch, and even then it must be an intermittent problem.

Craig

I believe a while ago Gregory & others mentioned switch cleaning as a good try
for some of these symptoms, since the gauge is switched by the contacts too. I
know I have that yet to do on ours.

Alex
79xj6

Craig Sawyers wrote:

This could be contagious! Same with mine. New valves (all three), new
connectors, new sender in one tank, and a refurbished one in the other,
correct voltage gets to all three. Fuel return flow goes to the correct
tank. No smell of fuel anywhere - the car is garaged, so I’d easily
smell a leak. But, same symptoms; change tank from one that is down to
1/2 full or so to one that was previously full - and it reads the same
as the half-empty one. But only intermittently! If I am driving while
I use the half tank, then change over, the other tank reads full. If I
leave it a while, it reads the same as the one I have been using. I’d
speculate that the fuel from one tank is syphoning over into the partly
empty one, except that the level in the partly empty one doesn’t go up.
Damned baffling.

I guess it must be down to the switch - it is the only thing left in
circuit that hasn’t been changed or cleaned!

Craig

[clip]

Here’s a clue to my disappearing fuel problem: I decided to leave it on the
right tank ever since I filled up both tanks. The right tank HAS NOT gone
down according to the gauge! I filled it up on Friday. I have done a lot of
drving in the Jag since then (at least enough that the gauge SHOULD have
gone down.)
I think this is an important clue in diagnosing what’s going wrong, just
FYI.

Add me to this troubled band. An hour ago I walked in from gassing up,
where I confirmed the same thing: both needles "within a gallon of each
other" after using half of one tank. Each tank tank took about 4 gallons.

s/s

Count me out. As of 2 hours ago, had left tank full, right tank little over half empty. Indicator was correct, right tank took about 5 gallons. Of course, I have a new dashboard switch, a new changeover valve, and I always run Chevron Supreme with Techron.

Paul Bentz writes:

I have a “disappearing fuel” problem where I . . .-----------------------------------------------------------------------------------------------------------------
Add me to this troubled band. An hour ago I walked in from gassing up,
where I confirmed the same thing: both needles “within a gallon of each
other” after using half of one tank. Each tank tank took about 4 gallons.

s/s
James
4/86 SIII (US) @87K in PHX – Keep the cause; the cause is just.


Get the Internet just the way you want it.
Free software, free e-mail, and free Internet access for a month!
Try Juno Web: http://dl.www.juno.com/dynoget/tagj.

Hey spectre-

I’m happy to hear you don’t use regular unleaded
petrol in your car. I have been fueling Madam Cat
with premium gas all along. Jeff wants me to put
regular unleaded in her-I can not seem to be able
to do it. Help? I need concrete reasons as to
why I am right-or if I’m wrong then, also why.
Thanks to those who respond.

Robin----- Original Message -----
From: spectre spectre@fok.com
To: xj@jag-lovers.org
Sent: Tuesday, November 30, 1999 10:12 PM
Subject: Re: [xj] Disappearing fuel

Add me to this troubled band. An hour ago I
walked in from gassing up,

where I confirmed the same thing: both needles
"within a gallon of each

other" after using half of one tank. Each
tank tank took about 4 gallons.

s/s

Count me out. As of 2 hours ago, had left tank
full, right tank little over half empty. Indicator
was correct, right tank took about 5 gallons. Of
course, I have a new dashboard switch, a new
changeover valve, and I always run Chevron Supreme
with Techron.

Robin: you are wasting your money. All Jaguars for North America, including
the might V12 are designed to run on 87 octane fuel: check your owner’s
manual; good fuel, like Chevron, that is, not bargain brands. If the engine
is aged and has considerable carbon build-up you may need to go to 89
octane, and for mountain use possibly higher, but stop giving the oil
companies your hard-earned money. I do not know what “premium” is for you.
Here in Canada we have up to 94 octane, with 87 being the regular (this is
NOT intended to start a thread on octane ratings; the Canadian and US
ratings are the same). My V12 runs perfectly well on 87, as do both the 4.2
litre cars. I found that our Sovereign, at 100,000 miles, wanted a higher
octane last summer when we took her into the Cascade mountains. I complied,
using 89 octane Chevron. No pinging. That is the test. Start at 87 octane:
if the engine does not ping, stick with it. Move up in octane grade only as
needed to eliminate the ping.
Gregory----- Original Message -----
From: Jeff & Robin Richards richards@eagnet.com
To: spectre spectre@fok.com; xj@jag-lovers.org
Sent: Wednesday, December 01, 1999 3:35 AM
Subject: Re: [xj] Disappearing fuel

Hey spectre-

I’m happy to hear you don’t use regular unleaded
petrol in your car. I have been fueling Madam Cat
with premium gas all along. Jeff wants me to put
regular unleaded in her-I can not seem to be able
to do it. Help? I need concrete reasons as to
why I am right-or if I’m wrong then, also why.
Thanks to those who respond.

Robin

----- Original Message -----
From: spectre spectre@fok.com
To: xj@jag-lovers.org
Sent: Tuesday, November 30, 1999 10:12 PM
Subject: Re: [xj] Disappearing fuel

Add me to this troubled band. An hour ago I
walked in from gassing up,

where I confirmed the same thing: both needles
"within a gallon of each

other" after using half of one tank. Each
tank tank took about 4 gallons.

s/s

Count me out. As of 2 hours ago, had left tank
full, right tank little over half empty. Indicator
was correct, right tank took about 5 gallons. Of
course, I have a new dashboard switch, a new
changeover valve, and I always run Chevron Supreme
with Techron.

Hi Gregory-

There appears to be a general consensus on the list that Chevron is the
best fuel in N America for these finicky beasts of ours. Unfortunately it
is not marketed in this neck of the woods (N Ohio). My local choices are
pretty much limited to BP, Marathon, Shell or Sunoco - and the “bargain”
brands, of course. Does anyone have any feelings about which of these
choices is the best?

Incidentally a recent survey of gas stations in Ohio found that 19% were
selling substandard fuel. Not a very comforting thought - and there is no
regular monitoring of fuel quality in this state…

Cheers - and thanks for any advice,
Loudon-
85 VDP, Josephine, currently running on BP 87 octane…

At 13:28 -0500 12.1.99, Dr. Gregory Andrachuk wrote:>Robin: you are wasting your money. All Jaguars for North America, including

the might V12 are designed to run on 87 octane fuel: check your owner’s
manual; good fuel, like Chevron, that is, not bargain brands.

Jeff & Robin Richards said…

Hey spectre-

I’m happy to hear you don’t use regular unleaded
petrol in your car. I have been fueling Madam Cat
with premium gas all along. Jeff wants me to put
regular unleaded in her-I can not seem to be able
to do it. Help? I need concrete reasons as to
why I am right-or if I’m wrong then, also why.
Thanks to those who respond.

Robin

The reason I use Premium Chevron in the big cats is simple -

  1. My ancient motorcycle does not run well on modern low octane gas and
    needs all the help it can get. It runs very well on Chevron Supreme. Same
    for the Jag; seems to prefer premium.
  2. Chevron Supreme contains a much higher dose of Techron than the lower
    grades do, just to clear out any deposits that might form and those that
    are already there.
  3. Seeing as how our cars are all getting up there in mileage, our octane
    requirements have increased as well (due to carbon build up in the
    cylinders increasing compression). As the XJ6 has no knock/ping sensor to
    tell the computer to retard the ignition timing, and as knocking and
    pinging can be fatal to engines that are weak, or any engine if it is
    allowed to continue unrepaired, I feel that premium gas is a small price
    to pay to get that added safety margin.
  4. Reformulated or “oxygenated” gasoline (not in Canada yet, as I
    understand, be thankful up there) contains more alcohol and has decreased
    performance when used in older vehicles, like ours. Therefore, it is
    sometimes necessary to go up a grade or more to restore performance.

Loudon Seth said…

Hi Gregory-

There appears to be a general consensus on the list that Chevron is the
best fuel in N America for these finicky beasts of ours. Unfortunately it
is not marketed in this neck of the woods (N Ohio). My local choices are
pretty much limited to BP, Marathon, Shell or Sunoco - and the “bargain”
brands, of course. Does anyone have any feelings about which of these
choices is the best?

One would thing you have Mobil stations up there. Anyway, in order,
Shell, BP, Marathon, Sunoco.

On Wed, 1 Dec 1999 14:39:31 -0600, Commander Spectre spectre@fok.com said:

Loudon Seth said…

Hi Gregory-

There appears to be a general consensus on the list that Chevron is the
best fuel in N America for these finicky beasts of ours. Unfortunately it
is not marketed in this neck of the woods (N Ohio). My local choices are
pretty much limited to BP, Marathon, Shell or Sunoco - and the “bargain”
brands, of course. Does anyone have any feelings about which of these
choices is the best?

One would thing you have Mobil stations up there. Anyway, in order,
Shell, BP, Marathon, Sunoco.

Here in South Africa, we have:
Sasol sold as Shell;
Sasol sold as Zenex;
Sasol sold as Total;
Sasol sold as BP;
Sasol sold as Sasol;
Sasol sold as Africoil;

…and probably a few I’ve forgotten.

At least we still have leaded (unleaded only accounts for about 15% of
sales).

Graeme–

Graeme Adamson, @Graeme_Adamson

Natural laws have no pity. - L. Long

Well, at least the SA government has taken a strong stand against oil
company monopolies! Of course we don’t have price fixing in Canada. The fact
that every single station, no matter what the brand, sells the fuel at
exactly the same price, and raises and lowers the price within, literally,
minutes of the other stations, has no bearing on this. We all know that it
costs the different companies exactly, to the 1/10th of a penny, the same
amount to produce a litre of gasoline, don’t we? Well, don’t we? No price
fixing here. We are now paying, in Victoria, $0.64.9 Canadian per litre of
87 octane unleaded. For US friends: there are a bit more than 4 litres in a
US gallon.
Gregory----- Original Message -----
From: Graeme Adamson claymore@iname.com
To: xj@jag-lovers.org
Sent: Thursday, December 02, 1999 9:42 AM
Subject: Re: [xj] Disappearing fuel

On Wed, 1 Dec 1999 14:39:31 -0600, Commander Spectre spectre@fok.com
said:

Loudon Seth said…

Hi Gregory-

There appears to be a general consensus on the list that Chevron is the
best fuel in N America for these finicky beasts of ours. Unfortunately
it

is not marketed in this neck of the woods (N Ohio). My local choices
are

pretty much limited to BP, Marathon, Shell or Sunoco - and the
“bargain”

brands, of course. Does anyone have any feelings about which of these
choices is the best?

One would thing you have Mobil stations up there. Anyway, in order,
Shell, BP, Marathon, Sunoco.

Here in South Africa, we have:
Sasol sold as Shell;
Sasol sold as Zenex;
Sasol sold as Total;
Sasol sold as BP;
Sasol sold as Sasol;
Sasol sold as Africoil;

…and probably a few I’ve forgotten.

At least we still have leaded (unleaded only accounts for about 15% of
sales).

Graeme

Graeme Adamson, claymore@iname.com

Natural laws have no pity. - L. Long