Hello again everyone, yes its me again with more silly questions lol.

Ok, the fuel gauge on my baby has not worked from the time I got it... The previous owner told me it has worked intermittently.

I have tried grounding the wire to see if the gauge responds but nothing....
I have bridged the two wires and still nothing.
I have taken the sender unit out and tested it..... it seems to function ok,
I took the sender unit apart and cleaned the tracks and tested again with a multimeter and it seems to check out.
I have tried the multimeter directly to the fuel gauge wires and get a reading of about 3.35volts, It seems a little low, but I guess you don't want too much current in the fuel tank.

So I am at a loss as to what else it could be.... unless it is the actual gauge on the dash that is not functioning. all I get is the red square constantly flashing on the gauge.

Is there a common fault with this system regarding the gauge itself?
I really would like to know how much fuel I have at any given time.

 

Rob,

First thing to check is the sender unit. Sender units that may have tight float rod bushings are labeled with date codes 2893 to 3693 and are faulty.

If your sender checks out ok, and you've tested everything else then chances are the fault lays within the gauge in the dash. Again, cracked solder joints are the main culprit and yes it means taking it out to check.

 

Robert,

You should be reading ohms at the two terminals on the sending unit. Ranges should be 18-20 ohms at full tank, 190-200 at empty.

I was going to ask the same thing as Jagfix, is there any odd behavior from the instrument cluster? Not sure if you have the digital or analog gauges, but if digital, as Jagfix implied, there could be issue with poor solder points on the instrument cluster circuit board.

Let us know, I've had to repair mine (digital) and will detail more info to you if needed.

 

thanks again fellas for the advice.
Ok took out the dash unit (it is digital BTW Rob) and pulled it apart.....
First thing I noticed was a hell of a lot of dust.... so gave it a good blowing off and dust off.
couldn't see anything unusual that stands out.....
Honestly I wouldn't even know where to start with it... there are transistor and diodes everywhere.... I did however replace the 4 light globes while I had it out..... the tacho and speedo never lit up before.... so another little job I can cross off the to-do list.

When I checked the sender unit, I did not have any idea of what the OHM readings should be, so I thank you for that info Rob...... I will take the sender unit out and not only test the OHMS per your specs, but also see if I can find the part no as per your references Jagfix38.
When I tested the sender, it was moving freely, I did disassemble the float arm and the pivot mount and check it all out thoroughly..... I even used a little emery on the points of contact and the tracks themselves..... and was getting full circuit on the multimeter..... however if memory serves me right... the OHM readings were no resistance at all.... so maybe still the problem.
Having said that.... the gauge still did not respond at all when earthing either wire to the body..... I should imagine even a digital dash will show full if grounded.
And the volt reading I got from the two wires was as I said 3.35 volts (or was it 4.35??) my memory is shocking lol.
Anyway connecting the two wires should have told the instrument panel that the tank is full. right??

 

Just out of curiosity....
Is the clock supposed to stay lit when the car is not in use and locked up?
I just went out to check the dash lights and admire yet another job well done and noticed before getting in the car that the clock was lit up.
It's only a dull green light.
I may be wrong, but I don't think it should remain on after the car is parked and left

 

Robert,

My clock doesn't stay illuminated after the ignition is turned off. I suspect the temporary insertion of the relay in the overcharge base. What I'm going to suggest if a PIA, but you may want to consider digging deep into the interior firewall and disconnecting the Central processor and remove/clean the ground for it and see if that helps. IIRC, the ground is located behind the duct work for the blower assembly.

In regard to the cluster, you didn't report any odd behaviour from the display, so I'm inclined to think you don't have and solder issues......yet. You will. The first items I would scrutinize would be the points where the connector wires terminate on the board, then move onto any solder joint which doesn't not have a shinny luster to the joint. Have a bright light and magnify glass to examine the joints. LOW WATTAGE IRON ONLY.

Same principle on the BFM's (Bulb Fail Module), they will fail eventually, especially the rear modules. Again, examine where the connectors terminate on the board, dull solder joints, and where the relays are connected.

 

we had an intermittent faulty fuel gauge on our 93. New sender fixed it. I too tried the ground the lead test to check the gauge and saw nothing. Sender was not too expensive and as you know, not too hard to change out.

 

ok Rob... looks like I still have a few gremlins to contend with.
Firstly as to the cluster...... everything seems to work great.... with the exception of the fuel gauge... which may still be the sender unit.
I did for a while have a problem with the VCM display being intermittent but I think it has stabilized now....
Ok you said you are going to suggest a "PIA".... again forgive my ignorance... I am not sure what that means.
As for the Central Processor..... if I am right.... that is located on the right side of the blower unit. yes?
And next ignorant moment IIRC? What s it and where do I find it?
I am sorry, I am still new to all the abbreviations...

Just out of interest.... I am not sure if the the clock was illuminated prior to the insertion of the overcharge relay. I can't say I ever noticed as I have not really driven her much at night yet. I very rarely get out of the house.

Also.... I am thinking I will removed the radio that has been installed...... it is not the original, that was in the boot, and I am not entirely convinced it is installed correctly and quite frankly I don't trust it.... it may have tapped into something it shouldn't have and this could also be a wire for the clock.

Just a thought.
I would like to put the original tape deck back in, but alas.... she no work



Update: Ok decided to remove the crappy stereo unit that was put into my baby by someone.
when I pulled it out, sure enough wires were just twisted and taped together and some had two or three wires taped together.
Anyway, I unraveled all the insulation tape and separated all the wiring and removed it completely
I will run without a stereo until I can find another original unit. (I have just sat the original in there to fill the hole)

Guess what... the clock now goes off when I turn off the ignition, so my suspicions here were also correct.
They must have somehow spliced into the clocks wiring causing a short.

Yet another task to be crossed off the to-do list
I am really sailing thro them, at this rate she will be fully restored and fault free in no time (sarcasm) ahhahaha

 

Thanks Firewrench,
I agree.... it shouldn't be too expensive and will at least eliminate the sender from the equation.
Much appreciate the input

 

I believe I read in one of the posts about a hard reboot or something.... where you touch the negative terminal to the positive or something...... is that a good idea or even recommended?
Just thinking that if that relay has done some change to the central computer or something.... maybe it needs a reboot back to default

 

the main factor for me with removing the sender unit was..... will I flood my boot with petrol, as I had no idea how much fuel was in the tank hehehe
So I slowly tapped off the securing ring and then ever so gently pried the seal at the top of the sender whilst still having the securing ring at the ready to whip back in at the slightest dribble hahahha
I was lucky... the fuel was well below the sender unit.

 

Robert,

If you havn't done so, follow the link and download the Haynes manual:

http://www.mediafire.com/?hx8bttsy4kxxr#3267xri9vx4v6

I believe the CPU is in the passenger foot (RH drive) well area, it has two 36-pin, and one 2-pin connector (IIRC)

If you really plan on getting into the vehicle, I would also suggest you purchase the official JDHT (Jaguar Daimler Heritage Trust) Cd-rom manual(s) for your vehicle. It will have all wiring schematics for every component and Technical Bulletins for the vehicle. Go here:

Jaguar Heritage. Search
Jaguar Heritage. XJ6 (XJ40) 3.6 LITRE (JHM1172)

One is for the parts and service, the other is the supplemental information

 

I don't know if this is a good idea, never tried it. It doesn't sound like good idea, but maybe someone knows if it's okay.

 

I don't think I like the sound of it either,
but I know I read something about in one of the forums though...... just can't remember where and I may have misunderstood it.



On that note... it is now 3:08 in the am and I need to shower and go to bed
Goodnight all

 

Hi Rob,
Tried to download the Haynes manual from the link but kept getting a pop up saying something about upgrading to download more than one file, and wouldn't let me get the file.
anyways I do have a service and repair manual (not Haynes) and it is fairly detailed, and also the original owners manual is pretty much full of info too lol

 

Update:
New sender unit arrived today and raced out and fitted it then got out the old trusty Jerry can and raced to the service station for fuel.
Had to use the wife's car as mine was totally dry now.... deliberately ran it dry so I could let it air out and then vacuum out the crap in the tank.

Problem solved..... fuel gauge now working, and to top it off it only cost me $20.50 for the sender..... brand new in the box.....

Had a lucky win on ebay..... only one other bidder and I didn't make my presence known until 30 seconds before the end of the auction...

So now I am one very happy camper.....
I had priced the sender units from various sources and the cheapest I could find was $227..... so $20.50 plus freight was a great win...... yeah Bob hehehehehe

Another little annoying job I can cross of the to-do list.

 

I agree with Rob. I believe the "reboot" procedure is something that is done on either X300 or X308 cars - I see it mentioned on one or both of those forums. But I have never heard anyone, let alone an expert, recommended such a procedure for an XJ40.

Cheers,

Don

 

thanks for the reply Don....
yeah I agree it is not something I would try....
I do not believe any good could come of such an act.

 

Bob,

If you still haven't been able to download the Haynes manual, PM me your email address and I'll send it to you. As far as I know, it's better than Chiltons or any other third-party XJ40 service manual, and it's an invaluable addition to the Jaguar service and supplementary DVDs from JDHT.

Cheers,

Don

 

Thanks Don,
I have managed to get a copy of it now....
It was just the program that it is linked to in the link will not let me download it...
It is wanting me to upgrade...ie pay for subscription.

But thanks anyway I do now have a copy