Saturday 17 September 2016

Eureka : Fuel Gauge repair

Another item I wanted to tackle is the failing fuel gauge. I don’t recall where I read it, but someone else also bumped into this issue and the permanent fix was to replace the fuel tank sender unit with the floater attached to it. On one of the Jaguar fora I also read these appear to be often flakey or having leaky floaters – which is not unusual since the car has aged.

So without doing any pre checks or testing I simply took the gamble and ordered this item. Including a new rubber gasket. Total costs including shipping € 51,-


I’m still amazed how much information can be found on this car. In any case it’s very useful and makes things easy. Rather then fiddling around or patching up the old unit I figured to buy it entirely new. And yes, I consider this item very affordable. If it turns out not to be faulty then I consider it preventative maintenance and I can rule out any problem with it for a long time.

The previous owner told me he ended up once at the highway with an empty gas tank. Clearly a situation I want to avoid and I don’t like to fill it up every 200 kilometers as I’m unsure how much is left. So time to get this fixed now.

The item itself is surprisingly very accessible and behind the spare wheel as that's where the fuel tank is located.


Also the fuel filter is located behind the spare wheel, good to know.


Removing the carpet and presto


And here it is. Picture taken to remember the wiring to the right connectors


Before replacing I did check the functionality first. Here with the current faulty one:


And here the new one, I simply connected the wiring on to it and lifted the floater. And it works perfectly so fault localized and I can go ahead to get the item replaced.



But as I have no clue how much gas is left in the tank I must first drain it.

I’m using the old skool trick to drain it, meaning applying the law of interconnected vessels. I still recall this vividly when our physics teacher explained this matter in 2nd grade at the age of 14. Of course he brought up the fact this method was being used to steal gas. He also mentioned it’s a tricky job as you can’t see the gas coming. I then advised him to use a transparent hose, which caused some raised eyebrows. I just happened to be very experienced in this matter as I grew up next to a garage. As youngsters we could play around and actually drive wrecked cars. And for this we needed gas which we simply drained from other wrecks. First lesson learned was to blow and listen if it had gas at all. Else you would sucking gas damp for a long time and I can reveal it will give you a nasty headache. Second thing we learned that gas flows very quickly and if to late you got it in your mouth. And I can reveal it taste exactly as it smells and it takes a long time to get rid of this taste. As such use a long transparent hose that allows to anticipate on the timing.


Removing and replacing the sender unit was another easy job.


 The removed unit was in a poor condition and heavily corroded. The floater itself was ok though:


But the pin attatched to the floater and the sender unit was completely stuck and wouldn't move at all. Thus explaining the failure. Not a surprise since the car was parked for 12 years in a showroom.

To avoid potential leaking I placed a new rubber seal

 And placing the new unit back into it


Then refilling it. I had already a full can of gas drained which I put it my other car. On the 2nd drain I think another 10 liter came out of it. So I did put that back and turned on the igntion. The meter went up but only very little. Hmmm. So on to the gasstation to do a proper refilling. To my surprise the meter didn't move up at all. Wicked. I now wonder what went wrong?

So now I will use the car for the rest of the week as a daily driver to empty out the gastank again. Sigh. Hopefully next week I can find out what's wrong.

Update 20-9-2016 : After touring around for the past 4 days I have ran into some trouble 3 times today! I will write a seperate blog about that. But just when I stranded for the 3rd time I noticed my fuel gauge was working all of the sudden. Not sure what happened though. As written earlier, I tested the functionality of it before installing. And I was pretty convinced I did everything properly. Apparently I did but still something must now have triggered it to start working. Weird. Here is the proof


Update 6-10-2016 : I came across this brass floater. Thought it was interesting to share

http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=108826


2 comments:

  1. Thanks for putting this information up. The fuel gauge on my XJS has just broken (stuck at empty), and it's good to see how easy it is to rule out the fuel sender unit!

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  2. I have to share my little bit knowledge about "How to Fix a Defective Fuel Gauge?"

    Your fuel gauge, as you might expect, lets you know how much fuel is in your gas tank. A defective fuel gauge can be a symptom of several problems such as a blown fuse, a broken circuit in the dash panel, or a fractured float -- the part attached to the sending unit in the intake fuel pump. In modern cars, you have two fuel pumps: the intake and main fuel pumps. The intake fuel pump is responsible for getting the gas up and out of the gas tank and registering the amount of fuel in the tank. The main fuel pump, located underneath the car, then grabs the fuel and sends it to the engine.

    Blown Fuse
    Step 1
    Access the fuse box. Consult your car’s manual to determine the exact location of the fuse box.

    Step 2
    Remove the cover of the fuse box using your hands. Flip it over to view the schematic diagram to determine which fuse controls the fuel gauge.

    Step 3
    Remove the fuse by hand and look at it in the light to ensure the element is not broken.

    Step 4
    Replace the fuse if the element is broken simply by inserting a new fuse where you pulled out the old fuse.

    Turn the ignition key to the “ON” position and see if the fuel gauge is now working. You do not need to start the car.

    Broken Circuit in Dash Panel
    Step 1
    Insert two specialty hooks on both sides of the dash panel to free up the panel enough to access the back of the panel.

    Step 2
    Disconnect all electrical wire leads to the back of the panel manually. This action is similar to unplugging an appliance from a wall socket.

    Step 3
    Pull out dash panel and place on the work bench. With a magnifying glass and ample lighting, inspect the back of the dash panel for a broken solder circuit. This is a slow and tedious process. If a broken solder circuit does exist, you will be able to see the breaking point in the circuitry.
    Replace the entire dash panel by inserting a new dash panel where the old dash panel had been. Reconnect all the electrical wire leads manually and then snap the new dash panel in place with a swift push using your hands.

    Fractured Float
    Step 1
    Consult your car’s manual to confirm the location of the access panel to the fuel tank panel. If the fuel tank panel is located in the trunk of the vehicle, remove all the contents in the trunk of the car which includes the spare tire and jack and all cluttered debris, and the cloth lining in order to find the access panel to the fuel tank. The fuel tank panel is usually fastened with 4 to 8 10-mm bolts.

    Step 2
    Unfasten the bolts with an air ratchet and 8 to 10mm sockets to remove the fuel tank access panel. Disconnect the wiring harness that leads to the intake fuel pump sending unit with your hands.

    Step 3
    Use the brass hammer over the brass punch to loosen the additional panel that leads directly into the fuel tank and then use your hands to completely pullout the panel which includes the sending unit.

    Step 4
    Take the entire sending unit to the work bench to inspect. You should now be able to visually identify if the float is loaded with fuel and see the fracture if one exists. The float resembles and works like a ping-pong ball in water.

    To confirm that this is the problem, attach the new sending unit to the wiring harness and place the key in the on position – move float up and down – the fuel gauge should go up and down.

    -Items you will need:
    Brass Hammer
    Brass Punch
    Standard Socket Set
    Air Ratchet
    Safety Goggles
    Magnifying glass
    Specialty Hooks for Dash Panel Removal
    Work Bench
    Flashlight

    Thanks For sharing. Appreciate your work. :)

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