 | Home > Td5 > TD5 fuel gauge |
 
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| mk1collector Member Since: 17 Sep 2009 Location: West Yorkshire Posts: 6769   
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Massively inaccurate
 they seem to go down faster the less fuel you have in. I just go by the mileage  |
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14th Oct 2014 4:31pm |
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| excossack Member Since: 22 Feb 2012 Location: North West Posts: 5743  
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Normally I am around the 280-300 mark from over full to 1/4 remaining. 1999 Defender TD5 110
Regards John M0VAZ Econet Station 48 no clock |
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14th Oct 2014 4:35pm |
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| ppad Member Since: 16 Nov 2012 Location: now, UK S Coast Posts: 218 
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excossack, I found it shocking, as a 1st timer to TD5, driving down to Chur (switzerland) last December, in the dark, on foreign soil, trying to figure km to miles and all of a sudden the gauge drops faster than a tart's drawers ...
and no idea how far to the next servo. The fuel gauge as installed is a device to sell Jerry cans. Sorely tempted to fork out shed loads for an extra tank if I'm doing more of these long runs. Sold the much modified 110 2.8, in Oz Brought the 90 home from Switzerland ... |
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15th Oct 2014 8:40am |
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| davew Member Since: 02 Jan 2012 Location: North Yorkshire Posts: 888 
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There are a number of issues with the TD5 fuel gauge.
1) The design of the tank and filler mean that the fuel level starts above the sender unit so when full it takes a while for it to register any change. 2) The shape of the tank isn't matched to the sender or the gauge so when it does start moving it's not very uniform 3) The speedo head has some "clever" electronics that convert the input form the sender unit into a signal for the gauge. These "clever" electronics actually prevent the gauge moving downwards, holding it at a position above the actual level until it's moved far enough for long enough to warrant allowing the gauge to drop. 4) The gauge reads higher for any particular signal when it's moving down than it does when moving up. This means that you will often find that turning the ignition off and then on again results in a reduced reading. On our 90 I bypassed all the above problems apart from 1 by building my own circuit to drive the gauge, bypassing the speedo head and calibrating the sender unit. It also allowed me to show a reasonably accurate fuel level in each tank in gallons, displayed on a separate LCD display. The sender unit in each tank is the limiting factor on it's accuracy but below 3/4 of a tank it is very accurate. http://www.yorkshireoffroadclub.net/ |
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15th Oct 2014 11:39am |
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| Anderzander Member Since: 08 Feb 2011 Location: Lancashire Posts: 999
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Wow !
Would you be willing to share how you did it please ? |
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15th Oct 2014 11:54am |
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| davew Member Since: 02 Jan 2012 Location: North Yorkshire Posts: 888
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It's pretty straight forward if you're used to playing around with PIC electronics. I'm happy to share the source code and circuit design. I've considered getting some PCBs manufactured professionally if there's enough interest.
I used a PIC16F886 as the basis for it, allowing me to have 4 ADC channels so I can read the sender input from both fuel tanks and the voltage level for both batteries all at the same time. I wanted to be able to see at a glance how much fuel we had in both tanks. I used the PWM output to drive the gauge, data lines to drive the LCD display and one output to drive an on board relay that operates when the main battery voltage exceeds 13.5 volts (used to connect the auxiliary battery to the main). It also has an output to control the low fuel light and an input to let it know which fuel tank is currently being used. The conversion from sender input to fuel quantity uses 20 calibration points for each tank. I configured the display to show the ADC hex value and added fuel 1 litre at a time, noting the hex value at each point so it's pretty accurate within the limitations of the sender unit. I've added some smoothing to the code for the gauge output, averaging the value over 5 seconds but not gone too far like the factory smoothing. The gauge and low fuel light booth reflect the state of the fuel tank being used at that time. The gauge is calibrated at 7 points with an allowance made to combat the difference when going up to going down. It then interpolates those set points to give a fairly accurate percentage reading of the whole tank. To cope with the fact that the sender design means that you need nearly 5 litres in the tank before it will start to display anything it will read empty when it gets to that point - better to slightly under read than over read at the bottom of the tank ! The LCD display can be seen here... showing fuel levels in both tanks, the dash by the side of the Main tank means that it is currently being used. The exclamation mark next to the aux tank level shows that it is low level. It alternates between fuel levels and battery voltages every 5 seconds.  Click image to enlarge The unit itself looks like this without it's lid... Click image to enlarge There's a bit more info on our blog: http://landytravels.com/category/fuel-system/ http://www.yorkshireoffroadclub.net/ |
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15th Oct 2014 1:45pm |
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| excossack Member Since: 22 Feb 2012 Location: North West Posts: 5743
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That does look an interesting bit of kit Dave. PCB made and then a component list as a DIY kit? 1999 Defender TD5 110
Regards John M0VAZ Econet Station 48 no clock |
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15th Oct 2014 5:46pm |
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| davew Member Since: 02 Jan 2012 Location: North Yorkshire Posts: 888
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Something like that might work, yes. The main problem would be calibrating the unit for an individual sender as it would require a programmer to download the firmware changes. Not insurmountable though, the PCB design includes an in circuit programming header so it can be updated in situ.
Having said that it probably wouldn't take a huge amount of work to add a couple of switches and a menu/setup function to the design that would allow the user to enter calibration values for the sender and the gauge. http://www.yorkshireoffroadclub.net/ |
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16th Oct 2014 12:51am |
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| Anderzander Member Since: 08 Feb 2011 Location: Lancashire Posts: 999
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It's looks brilliant and very useful - but above my knowledge level to implement by quite a margin at the moment !
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20th Oct 2014 11:27am |
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| shazzy90 Member Since: 17 Dec 2010 Location: tyneside Posts: 489 |
very good but well above my diy skills,you should take your design to the dragons den of landrovers and get a investment,very good bit of kit
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24th Oct 2014 10:43pm |
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| shazzy90 Member Since: 17 Dec 2010 Location: tyneside Posts: 489 |
I do not drive my landrover often but the wife drives it every day and the fuel gauge works very well,it always has the yellow warning light on every time I go to use it, THIS IS THE TRUTH she does not know how to use a fuel pump after 12 years of driving
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24th Oct 2014 10:53pm |
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| Fatboy Slim Member Since: 04 Feb 2008 Location: Bridgend Posts: 1006 
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Feel your pain shazzy...............My Mrs is a fully paid up member of the yellow light on club as well.
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25th Oct 2014 1:42pm |
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| roel Member Since: 08 Aug 2009 Location: Lelystad Posts: 2039  
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Luckily my wife doesn't want to drive my Land Rovers.
But here Volvo also happens to be in need of petrol if I want to use it. Roel 1984 90 2.5 na Diesel - RR V8 (1994-2001) 1997 Camel Trophy Discovery 300TDI (2001-2009) 2005 G4 Discovery III 4.4 V8 (2008-2018) It's gone but it still hurts. 2003 90 Td5 (2009-now) |
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25th Oct 2014 2:29pm |
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| JWL Member Since: 26 Oct 2011 Location: Hereford Posts: 3443 
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There's only me that drives mine but I swear it must go out and have some fun while I'm not looking
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25th Oct 2014 2:35pm |
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