Freelander 1 Fuel Gauge Fault, AMUSING and SOLVED

[andyfreelandy]

Wife's 2002 TD4 displayed 1/4 full on fuel gauge. Filled tank, tank shows 1/4 full!!

Have switched ignition on and off and thumped sender in tank, my initial basic diagnostics!! No change.

Ran the icarsoft ipack check and whilst it dropped the gauge to zero as it always does, it then registered an ipack comms error.

Is it worth stripping the sender out or is it straight to the dash display unit??

Gauge has worked correctly previous to this fill up.

Thanks.

 

[andyfreelandy]

As the gauge is dropping as fuel is used, so it acts like 1/4 full on the gauge is full in the tank and drops accordingly, I think the sender must be OK??

Anyone had similar please?

 

[Nodge68]

The fuel gauge is a simple resistance, which decreases or increases (year dependent) as the fuel is used, The resistance of the sender is calibrated to give the gauge a reasonably accurate indication of fuel level in the tank.

If the gauge doesn't go all above 1/4, even when the full tank is full, then it's very likely to be the sender is faulty. I've got a working early (2001) one somewhere, although I've no idea where just now.

 

[andyfreelandy]

Thanks, it is the fact that it has dropped from 1/4 tank as the full tank is used that makes me think the sender is working. Also the ipack comms failure on the icarsoft. What happens to variable voltage when it goes into the ipack? Does it feed the gauge direct and also feed the computer or is the signal fed via the computer to the gauge?

 

[Nodge68]

I think the Ipack comms issue is a red herring.
As far as I remember, the fuel level sensor just sends variable voltage to the Ipack, which then converts it to digital and then displays the interpreted level on the gauge.
The Ipack doesn’t broadcast the fuel level on the can, unless the low level light is on, at which point it informs the engine ECU (petrol only) that the fuel is low, so the ECU can ignore a misfire, should one occur.
I don't believe the diesel EDC is smart enough to monitor individual cylinder firing pulses, so this low fuel level strategy probably isn't implemented on the TD4 models.

You can test the fuel level sensor easy enough. Just short the 2 sensor wires at the tank sensor plug. If the gauge goes full scale (either full tank or empty), then you've proved the rest of the system.

 

[andyfreelandy]

Yes will test by a link at the sensor. Have used the WOW software to activate the gauge and it goes to half full. It also does this on a good vehicle so I think the tank is the place to start.
Just didn't want to open the tank seal unless I had to. According to Rave the Ipack sends a signal to the tank resistor which is grounded and as you say converts it to a gauge reading. Whatever happened to moving iron meters??? Dooh..

 

[Nodge68]

Moving iron, or thermal gauges went years ago. The needles in modern car Ipacks are now all moving coil meters, although many new cars are fitting LCD screens instead, as this is much cheaper to implement, but looks more expensive, so a premium price is charged for the privilege of having an all digital Ipack.

 

[ian mitchell]

mine is a fl2 so probably different.but my gauge sticks every so often
,so i found disconnecting the battery works.i think the fl2`s computer works out
your driving style,and then calculates your fuel consumption,so disconnecting battery
resets the computor and the fuel gauge then shows more fuel than before
until it recalculates then usually drops again due to my driving style.

but i dont think the fl1 works like that so i am actually talking b******s

 

[andyfreelandy]

The gauge and sender is more complex than I thought. I disconnected the sender at the plug, green and black wire for the gauge. I made a new earth connection to it expecting a full gauge to be displayed. It didn't. The only way I could increase the gauge needle was to tap the earth on and off, like morse code!!
I am unsure of the signal being sent out by the ipack to the sender, but having checked the cable and the earthing and by inserting resistors at the sender end of between a few ohms and a few 10s of K ohms nothing could be read. Gauge stayed at empty.

So I turned my attention to the ipack and instrument panel. I substituted a spare and the gauge worked correctly.

Just out of interest I connected the sender cable to earth with the working instrument panel and same zero fuel result. High resistance also zero on the gauge.

Replacement instrument panel has solved it but not sure now how it works. There must be a coded signal that does sommat clever


If anyone can fill the knowledge gap it would be good.
BTW I have just added 27,000 miles or so to the odometer. Never mind, have logged it in the service book. Anyone know how to change the mileage to correct this anomoly???

Weirdest fault ever. Rave simply says that the ipack sends 'A SIGNAL' to the fuel tank. Wonder what it is!?

 

[andyfreelandy]

So thought I'd got it, hey how complex can a simple fuel gauge be!?!

But no, Frebbie had other ideas. Went for drive to test it, all dials and temp fine. Fuel gauge seemed high for the miles run.

Carried on, fuel gauge is getting fuller!!

So, the ipack must have come from a later car with the sender the other way around.
Then, engine fault light comes on and car splutters. Limped home. Codes P1190 fuel rail plausabilty and P1643 Can bus other are now stored!!
Also, when restarted a loud rushing noise in tank.
Figured the diesel management unit and ipack were not happy with each other!!

Swapped back old ipack and instrwnt cluster. Same fault on fuel gauge. Showing 1/4 when about 3/4 full.
Instead of applying a short circuit I read up on the actual values of resistance on the tank unit. About 100 ohms for full and 600 ohms for empty. Sure enough when these values (120 ohm and 620 ohm) were applied the suspect instrwnt cluster showed full and empty respectively.
A short circuit does not show a result on the gauge, just empty as it is with open circuit.
So, then measured resistance in the tank sender. About 550 ohms. Concluded tank unit duff and ordered a replacement.
However, the gauge has a lot more to do with the engine running than I thought. Assumed tank unit made gauge display and that was all. Wonder what happens when the dmu gets a signal of tank empty and tank isn't empty?? Will it shut engine off?
So for benefit of others, test at sender end with resistors, not a short circuit.
Will conclude this thread when tank unit is replaced. Obviously will check resistance of new one before fitting with float level at full and empty.

 

[Nodge68]

That's an interesting discovery Andy. I've never actually needed to fool the gauge, but it's good to know the resistance needs to be in a narrow window. I suspect this is done so the Ipack could register an open or short circuit situation, and log the necessary code.

It's interesting that the different Ipack upset the engine, as the engine will run without the Ipack data connected, as Ali discovered in his EV investigations. Although this was on a Facelift, with the CAN bus disconnected, so maybe the earlier K line bus system is more fussy.
Interesting.

 

[andyfreelandy]

So quick recap. Wife put 50 quid in tank. Gauge stuck at 1/4 full. Checked with 2 resistors to simulate full and empty and all good. Measure resistance from sender and it showed empty. Ordered new sender.
Today armed with new sender I took the old one out and,,, my word, no fuel in tank, about 1 inch that is all.

Tested old sender by moving float, all good.

Reinstated car to as it was and set up to question wife!!
So what happened is that she used a pay at pump, Had a tight stretched hose so only put 50 quid in so as not to spill it over.

Went on line, checked bank account, she had put 5.00 in!!!!

Also, pump was running really slowly

So no fault with car but now know how gauge works, see above.

Glad she didn't adopt the, I'll drive it 300 miles and fill up again strategy!!

It would have ended badly in the middle of nowhere I expect.

Have a smile at our expense!!!!!

 

[Alibro]

That's an interesting discovery Andy. I've never actually needed to fool the gauge, but it's good to know the resistance needs to be in a narrow window. I suspect this is done so the Ipack could register an open or short circuit situation, and log the necessary code.

It's interesting that the different Ipack upset the engine, as the engine will run without the Ipack data connected, as Ali discovered in his EV investigations. Although this was on a Facelift, with the CAN bus disconnected, so maybe the earlier K line bus system is more fussy.
Interesting.

I didn't drive any further than across my driveway so I guess it may have complained more had I driven down the road. I guess we'll never know.

Good to hear you got it sorted Andy.

 

[Nodge68]

I didn't drive any further than across my driveway so I guess it may have complained more had I driven down the road. I guess we'll never know.

Good to hear you got it sorted Andy.

It's quite handy to know the resistance needed (volt drop) for a full and empty tank Ali, as this information might well help if you want to use the fuel gauge as a battery charge indicator on your FL1 EV.

 

[Alibro]

It's quite handy to know the resistance needed (volt drop) for a full and empty tank Ali, as this information might well help if you want to use the fuel gauge as a battery charge indicator on your FL1 EV.

You're right John, I hadn't thought of that, I'll repost the info in the Freelander EV thread so it's not lost.
Thanks Andy, Top job.

 

[andyfreelandy]

I'll repost the info in the Freelander EV thread so it's not lost.

Heather is pleased that she made a contribution to the important EV thread!!

 

[Nodge68]

You're right John, I hadn't thought of that, I'll repost the info in the Freelander EV thread so it's not lost.

I'm thinking of a practical and safe way to achieve this.

 

[Alibro]

I'm thinking of a practical and safe way to achieve this.

Already done.

 

[andyfreelandy]

However.... Please be aware that the facelift sender appears to work in reverse, certainly the ipack fuel gauge from a later car reads backwards so probs sender is opposite to the above.