What causes the fuel hand guage to flucuate. One day i put gas in the car and the hand went to empty. it goes back up sometimes and then it goes right back to empty.

 

Need advice on what causes the fuel hand to flucuate on 2003 jaguar xj8

 

Welcome to the forum holiday,

I've moved your question from General Tech Help to X350 forum. Members here with the same model will be able to help.

Please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some info about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham

 

Holiday, I have experience issues with fuel level sensors acting goofey and actually had one that read backwards. Odds are, you are looking at a sensor issue inside the gas tank. Unfortunately, the fix is to access the top of the tank (normally means dropping the gas tank) and then replace the level sensor. The sensor should be fairly cheap unless they force you to buy the whole assembly (which would include a new fuel pump). But if you do some looking around, you should be able to find an equivolent part and then get just the sensor at the local auto parts place.

 

Hi holiday,

If your problem is with the fuel level sensor or sender, I don't think you'll have to drop the fuel tank. The problem could be in the wiring between the sender and the instrument cluster, but senders are known to fail with age.

If your 2003 XJ8 is an X350 with an aluminum/aluminium body (which is the model this forum is dedicated to), many fuel level sensor issues will trigger a fault code or Diagnostic Trouble Code (DTC) that can be read with a scanner that can read Jaguar-specific codes. Two examples of fuel level sensor faults are:

P0460 Fuel Level Sensor to Instrument Cluster Circuit
P193300 Fuel Level Sensor CAN Signal fault

On the X350, there are two fuel level sensors and they can be accessed through ports below the rear passenger seat. You can download the X350 Workshop Manual in five parts from the Download section under the "XJ8 'HOW TO' quick links" near the top of the list of threads in this forum. The fuel level sensor is in the Powertrain section of the manual, and is mentioned in several places, including beginning on page 3222 in the section on draining the fuel tank. Procedures for testing the fuel level sensor begin on page 3283.

If your 2003 XJ8 is an X308 with a steel body, the fuel level sensor or sender is mounted on the back side of the fuel tank, and can be accessed from the trunk by removing the trunk trim. Before removing the sender, be sure your fuel level is as low as possible, ideally 1/4 tank or less. You can probably download the X308 workshop manual from the HOW TO links at that forum. I don't know if the X308 will trigger any fault codes related to the fuel level sensor, but it would be worth having your car checked for fault codes.

Whether your car is an X350 or X308, it is worth going to the X308 forum and downloading and installing the Jaguar Electronic Parts Catalog (EPC) which will allow you to look at parts diagrams and to look up part numbers, which is very handy when shopping for the best price on parts. If your car is an X308, you can also view parts diagrams and look up part numbers at www.jaguarclassicparts.com, the official parts service of the Jaguar Daimler Heritage Trust. Independent Jag specialists such as forum sponsor SNG Barratt are a good source for parts, as well as Coventry West, Welsh Enterprises, and online Jaguar dealers jaguarmerriamparts.com and gaudinjaguarparts.com, which offer discount prices on OE Jaguar parts. I have not heard of equivalent Jag parts suppliers in Canada but perhaps one of our Canadian members will chime in.


Hi Thermo, I notice that since 2008 you have been thanked 1,294 times but have never thanked anyone else. Has this forum really been of so little value to you? Just curious...

Cheers,

Don

 

The gas hand read this morning correctly for about 20min while driving then it dropped back down to empty. So do you really beleive it is the sensor. Also i had the thermostat replaced and all of a sudden the restricted performance light is on. it comes on and goes off, but not every day. They say it is the knock sensor. I do need new brakes, but they are not that bad yet. Could this be the cause of the sensors going off. Is there a way to check for a faulty wire without replacing the sensors first. My car has only 119000 miles on it. it was running perfectly fine until i had the thermo replaced. i dont trust to take it back to the person that repaired it. thnks for any advice.

 

Hi holiday,

Before we go any farther, we need to clarify the model of your XJ8. Does it look more like this photo, which is a factory code X308 (steel body):




Or does your car look more like this photo, which is a factory code X350 (aluminum body) model introduced in 2003:




Knowing which model car you have is important because the mechanical and electrical details are very different. If you'll let us know the answer to this question, we'll be able to proceed with a clear understanding of your car.

Cheers,

Don

 

To put it another way ... if the last six digits of the VIN begin with ...

an F it's an X308

or if they begin with

a G then it's an X350

 

the x308

 

Okay holiday, now we know what vehicle we're discussing, but we're in the wrong forum. We'll get more knowledgeable answers from X308 owners.

Graham, is it possible to move this entire thread to the X308 forum, or do we need to start over?

Thanks!

Don

 

Don,

It's back in X308 ..... again!

Graham

 

Okay holiday, now we're getting somewhere. The sensor or sender is a likely suspect, but it could be the electrical connector to the sensor, the sensor wiring harness, etc. The sender is mounted on the back face of the fuel tank, which can be accessed via the trunk/boot. Remove the trunk trim on the bulkhead to access the sender. See part 8 in the diagram below:

Fuel Tank-3.2/4.0 Litre-V8-Normally Aspirated-Unleaded - Parts For XJ Series from (V)812317 to (V)F59525 (X308) | Jaguar Classic Parts UK

The long bent wire that extends to the right of the sender body has a rectangular plastic float on its right end. The float rises and falls with fuel level in the tank. The sender is affixed to the tank by a locking ring, part 9.

Unfortunately the download link for the X308 Electrical Manual appears to be broken - I've reported it to the Admin. I have a copy of the manual on another computer and will PM it to you.

You can check the integrity of the wiring attached to the fuel level sender (I don't know if one or two wires are attached). Check for looseness or corrosion. With an ohmmeter, you can measure the resistance of the sender. Add a gallon of gasoline/petrol to the tank and measure the sender resistance again to see if it changes. You can also check the resistance when the dash gauge goes to empty to see if the sender resistance has dramatically changed.

If so, you probably need a new sender. Replacing it is easy. Run the car till the gas level in the tank is low, ideally 1/4 tank or lower (it may be difficult to know for sure with your gauge operating erratically). To remove the locking ring you tap each lug once or twice, working your way around to each lug, to rotate the ring counter- or anti-clockwise (I think! Check the locking tabs on the tank to be sure that's the direction the ring needs to go to be freed from the tabs). With the ring loose, the sender just pulls out of the tank (carefully to avoid snagging the long bent rod and float on anything).

If the sender resistance seems okay even when the dash gauge drops to empty, with the Electrical Manual you can determine where the other end of the sender wiring harness connects (possibly at the instrument cluster or elsewhere). By connecting an ohmmeter to both ends of the harness, you can measure for high resistance or a short to ground.

Off the top of my head, I don't believe any of these issues is related to your fuel level gauge. You might post these questions in a new thread after you get the fault codes stored in the computer read by a mechanic who has a scanner that can read Jaguar-specific fault codes. Without code information, it will be difficult to give you specific advice.

Cheers,

Don

 

Thanks for the info. Really appreciate it. Now one more question. Will needing new brakes cause the restricted performance light to come on or could it be something more common than that. Also is it common with only 119000 miles for this sensor to come on. The light came on a week or so later after we had the thermostat replaced. the car was working fine before that. thanks

 

HOliday, something that you can try is before you start the car, depress and hold down the TRIP button. With the button depressed, start the car. Once you see the ODO say something to the effect of "TEST" or "ENGINEERING TEST", release the Trip button. At this point, you have your instrument cluster in a diagnostic mode. You will want to depress the TRIP button repeatedly until you see the ODO say "F1 XXX" where XXX is a number ranging between 000 and 255. When things go south on you, what does the XXX part read? If it reads 000-009, then you have a wiring problem at the sensor most likely unless you have a damaged harness (you would need to disconnect the sensor using the ports under the rear seat and if the reading remains the same, then confirmed to be the harness, otherwise it is the sensor). If it is reading 010-254, then you have a "good reading" of the sensor and your problem most likely is in the instrument cluster. If you are reading 255, then you have an open in the wiring or the sensor (you can prove the wiring good by shorting 2 wires together, if you are wanting to do this, let me know and I will tell you which wires to short together, then you should see the instrument cluster drop to 000-009 if the wiring is good).

To get out of the diagnostic mode, you can either hold the TRIP button down for 3 seconds or simply turn the car off.

You will also need to do this with the next position (F2 XXX). If both F1 and F2 are reading good values (ie, between 010 and 254), then your problem almost definitely is in the instrument cluster.

 

Hello, I have a 1999 xjr with same problem but mine happened after I replaced my
fuel pumps my fuel level just shows empty. I have taken out the sender and checked the
resistance of the sender and it seemed good, I even got another unit. I checked to see if there was any voltage going into the unit and didn't see anything. is there a fuse or anything in the circuit? I can't find the wiring diagram for the x308 xjr I will try the
trip test next

 

Now that is something not everyone will know. Thx!

 

well tried to get mine to get in the "test" mode and unable to do it... I am seeing an
open ckt on the red/white and green/brown wires going to the sending unit so will just
have to keep trying , really don't want to take apart the instrument pod but might be
next step?

 

powell, you should be able to get the instrument cluster in the test mode. Are you sure you are not releasing the trip button too soon. You have to depress the TRIP Button and while it is depressed, start the car, and then after a few seconds of the car running, the instrument cluster will finally say "TEST" (or the like). It is at this point that you can release the TRIP Button.

 

Good info on here, I have a question though (don't mean to hijack the thread, but), if you can get to the fuel level sender through the trunk/boot then why does everybody have to drop the tank to replace the fuel pump(s) ?

 

on the x308 no need to "drop" the tank as the tanik is behind the rear seat you need to
remove the fuel lines and straps and pull the tank out very carefully the fuel pump or
pumps on sc model can be removed thru the top of the tank.