Whene ever I drive this car I notice that the fuel gauge needle tends to jump to the left as if I lost some fuel or some thing. This car is still new to me so I don't know if it's normal or am I getting poor gas milage. I've tried all I can think of: new fuel filter, bought a K&N air filter, checked tire pressure and put in new plugs ( which made some difference) But Im still not satisfied. I don't see this happen in other cars. What could it be? is this normal on jags? I've heard they do bad on gas milage but It cant be that bad right?

 

David what is your instrument cluster telling you the MPGs are? There is even a setting to see "instant mileage".

There are alot of related MPG threads here in the "S Section". There are guys stating that they get up 28 mpgs on the highway. It seems that the 3.0, 4.2 and the STRs get pretty amazing mileage when driven accordingly.

I just looked at Joyces Driver Information Center (DIC),she drives majority city, the reading is 18.7 mpg and the average speed is 26 mph. The DIC is located at the end of the blinker lever.

 

Hey rick
well the computer says im gettin on average 20.4 mpg and my average speed is 20 mph with little stop and go intervals depending on traffic. how accurat is the computer?at stop lights I start the car off slow to not burn so much gas but I drive with gas prices going up so high I want to fill up as little as possible. But the thing that bothers me is how the needle for example, lets say it's at the ping just before the F on the fuel guage, as im driving the needle will just shift over to the half a tank ping. with the new spark plugs put in it made a difference the jump is not as big as it was before.

thanks rick

 

I don't know if this helps but its a TSB about the fuel sender:

S310-07
S-TYPE
DATE 06/05
Amended 10/05
MODEL
2003-05 MY
S-TYPE
VIN
M44998-N52047
Fuel Level Sender - Available Separately From Pump - Replacement Procedure
Remove and destroy Bulletin S310-07, dated 06/05. Replace with this Bulletin.
Updated information is shown with asterisks and black bars.
Issue:
This Technical Bulletin is for information only, to inform dealers that if there is a fault with the fuel level sender unit, the fuel level sender unit can now be replaced as a separate part on both normally aspirated and supercharged vehicles.
*Action:

***EDITED OUT FUNKY DIAGRAMS*****

 

David, keep an eye on your gauge, if the needle moves around a lot, from full to half, back and forth, you may have a fuel pump problem. The computers readings...instant mileage; range; average mileage; are apparently tied to the gauge. When the needle shows full, your range, etc. will show one number. When the needle drops to half, those numbers will drop accordingly and can be erroneous even if the tank is full.
My gas gauge needle was doing the flippity floppy thang about a year and half ago, the dealer replaced the jet pump and a couple of other items, all under warranty. I'll have to find the work order (a bit later)and essplain what was done.

 

I'm going to reach out to my Jag contact this week and see if this TSB might need to be performed on my car.

 

David, maybe one of these TSBs (maybe in the stickies?):
S310-02 Erratic Fuel Gauge Reading VIN M45255-N11732
S310-04 Erratic Fuel Gauge Reading VIN M45255-N13896

I think Bob's will be out of those VINs.

 

JagV8;
Can you post a PDF of S310-04 TSB? I have the earlier one S310-02. I have attached it in case anyone can use it.

joycesjag;
Can you post a PDF of S310-07? I know you included the text but I try to keep as many TSB's as possible in PDF.

Thanks in advance!
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It's almost identical, mainly the part numbers are different. I got the VINs slightly wrong as I'm ROW not NAS.

 

Work done as promised from dealers notes:
Checked codes, got B2627, B1202, checked raw fuel thru inst. pack.
RAW 1 91, RAW 2 255.2
Open circuit, gauge was reading full but dropped to 1/4 tank. Checked resistance at pump, RH side 300 ohms and LH side at 3.6 kohms. Replaced both pump and jet pump.

P/N's
(1) XR852870 Assy-sender & pump
(1) XR852864 Sender
(2) XR848118 Gasket

No charge--warranty...

I understand that this problem is caused by the fuel in the tank getting so low that the pumps are above the fuel level and overheat which can lead to their failure.
I don't know how low the fuel in the tanks can go to keep the pumps submerged, but I don't let mine go below 1/4 tank if at all possible. The service guy said that if it were out of warranty, it would cost approx. $800-$1000 to repair.
Beware to those who let their tanks drop too low, you could have the same problem...

 

What is the difference between a fuel pump and jetpump? has any one fixed this problem them selves rather than taking it to the shop or dealer?

 

The S Type has two very different fuel systems. The STR (2003 and up) has two fuel pumps feeding the engine directly with the second one coming on line at 3K rpm. All other S Types and the Lincoln LS use the jet pump/fuel pump setup. This uses the jet pump to only move fuel from one side of the fuel tank to the other. The main fuel pump picks it up and feeds the engine from there.

The tank is under the rear seat and in front of the rear axle for safety reasons. This means the drive shaft splits the tank down the middle. If the jet pump fails you will run out of gas with fuel still in the tank.

You certainly can change fuel pumps yourself. It's a bit easier than it use to be. Underneath the rear bottom seat cushion are two access ports thru the body to the top of the fuel tanks.
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thanks for the info. where can I get the special tool that the JTIS shows to remove the locking rings?

 

where exactly is the fuel sender? is it the fuel pumps?