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llessur



Member Since: 15 Nov 2011
Location: Hereford
Posts: 151

United Kingdom 
Request for a second opinion on Fuel Gauge
I have a 2008 2.4 TDCi 90 and the fuel gauge reads above full. (full deflection) Now when I have seen similar on other vehicles it has been a short to earth. Would this be true for my Puma ? I was going to unplug the connector behind the offside wheel arch flap and drop a multimeter across the green / orange and yellow / purple (wire colours based on a search on here) to see if the short lies in the wiring going forward to the gauge------------ or back to the sender.
Just in case I need a sender I came up with a part number of WQB100440 but with prices in the £130 to £180 range I wondered if this was a very expensive sender or if I had the part number wrong and the part I was looking at was the pump / sender combined. My understanding was that the 2.4 Puma did not have a pump in the tank. Have I got the part number correct ? Do senders short, when they fail ?

If possible, would someone in the know, just have a look at my info / plan to see if it makes sense as I am like many owners, breaking new ground with just about all the issues that crop up on the Defender.
Thank you
Post #794734 23rd Sep 2019 6:45pm
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Martin
Site Admin


Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6460

United Kingdom 2015 Defender 90 Puma 2.2 XS CSW Montalcino Red
Is it stuck on full deflection or does it start off above full then drop as normal?

The Puma instrument pack isn't like a traditional moving needle gauge where less resistance -> more current -> more deflection.

The sender resistance is measured as a voltage drop by the instrument pack microprocessor which does the damping (and error checking) and moves the needle and turns on the warning lamp when needed. It also sends the fuel level out as a CAN bus message for the engine ECU to use.

So, if you see what I mean, the needle isn't directly connected to the sender.

There also isn't a wheelarch connector to unplug to check this. The only inline connectors in the fuel sensor circuit is the pair mounted on the top of the driver's footwell - a 14 way grey connectors alongside a 1 way and 4 way.

The correct replacement in-tank pickup/sender part for a 2.4 90 is WQB100430. There's no pump on it, the extra bit you're not expecting to see is the fuel swirl pot.

You could remove the instrument pack connector and do a resistance test of the sender as it stands now.  1988 90 Td5 NAS soft top
2015 D90 XS SW
Post #794777 23rd Sep 2019 9:07pm
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Martin
Site Admin


Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6460

United Kingdom 2015 Defender 90 Puma 2.2 XS CSW Montalcino Red

Click image to enlarge


C0376 and the matching C0390 (on a 90) are the 14 way ones mentioned above Smile  1988 90 Td5 NAS soft top
2015 D90 XS SW
Post #794778 23rd Sep 2019 9:10pm
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blackwolf



Member Since: 03 Nov 2009
Location: South West England
Posts: 16808

United Kingdom 2007 Defender 110 Puma 2.4 DCPU Stornoway Grey
My 07 Puma gauge was originally very non-linear and would be well off the scale if the tank was full, remaining that way for around the first 100 miles (actually about 1/4 of a tank). It would then drop at an accelerating rate, so the last 1/4 of the tank accounted for about half the FSD (full scale deflection) of the gauge.

I changed the sender a year or so ago after the original split (for a new genuine part) and the new one was perfectly linear. It's still well of the scale when full, but now drops evenly as the fuel is consumed.

The replacement sender for the Puma, which is essentially the same as a TD5 but without the pump, was shockingly expensive and was about the same as a TD5 unit complete with pump, another depressing example of LR's absolute rip-off pricing. The part number you quote (WQB100440) is as far as I know the correct one, but it doesn't help that firms that should know better, such as LRDirect, describe it as "In tank fuel pump & sender..." when it does not include a pump! I almost wonder whether the description was carried over from the TD5 accidentally, and the price was also carried over accidentally.

I haven't tested it, but generally fuel gauges go to FSD if they are open circuit, so it is possible that you have a faulty connection or broken wire. Unfortunately the sender is completely inaccessible unless you drop the tank, and even accessing the connectors on the unit require the tank to be lowered. It is not a pleasant job.
Post #794780 23rd Sep 2019 9:29pm
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llessur



Member Since: 15 Nov 2011
Location: Hereford
Posts: 151

United Kingdom 
Thank you all
I will start with a resistance check at the instrument pack connector.
(The full deflection is only after the ignition is turned on)
I will let you know how I go, but if it means dropping the tank I will probably look at changing the hoses and sender at the same time.
Post #794802 24th Sep 2019 6:34am
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