farmer_joe Posted February 26, 2016 Share Posted February 26, 2016 Hi guys. I've been having an issue with my fuel gauge, for the past year or so! If you fill it up it reads full and as you use the diesel it works to exactly half full and then doesn't read any lower. It does sometimes waver about around the full mark when you first full it up then it settles down. It worked properly up until I had to change the tank and hasn't worked since. I thought initially the float was binding causing the issue but made sure it doesn't touch anywhere so that's not it. When it's below half a tank, if you remove the sender from the tank and then reinstall it it reads correctly for the remainder of that tank. Done a search but didn't turn up an answer. It's a 1984 90 that's had a 200tdi disco conversion if that makes a difference. I don't want to shell out on a new sender until its confirmed that's the cause of the problem! Any advice gratefully received. Joe. Quote Link to comment Share on other sites More sharing options...
Tanuki Posted February 26, 2016 Share Posted February 26, 2016 Simple test: First, disconnect the wire from the tank-sender unit and - with it unconnected - see what the gauge then reads when you turn on the ignition. Second, use a piece of wire to connect the tank-sender wire to a good reliable earth and turn on the ignition. See what the gauge reads. One should give you full on the gauge, the other empty. If this is the case then the in-tank sender is faulty and needs replacing. If it's not the case then you have a wiring/gauge/voltage-regulator issue. It could be that the tank-sender unit isn't properly earthed. Quote Link to comment Share on other sites More sharing options...
farmer_joe Posted February 26, 2016 Author Share Posted February 26, 2016 Thanks for that Tanuki, I'll try it tomorrow and see how it goes. Quote Link to comment Share on other sites More sharing options...
vulcan bomber Posted February 26, 2016 Share Posted February 26, 2016 Check the earth is intact on the back of the gauge. Quote Link to comment Share on other sites More sharing options...
Disco-Ron Posted February 27, 2016 Share Posted February 27, 2016 I had this last week, I knew the gauge was wrong as mine is a fuel hungry v8.... I removed the pump/pick up from the tank and looked in to see the float stuck on the baffle. .... a simple kink in the float wire sorted it.... remove the pick up and look in...... Quote Link to comment Share on other sites More sharing options...
Maverik Posted February 27, 2016 Share Posted February 27, 2016 Also check the wee resistance contacts on the sender float scale, they can get quite dirty and need rubbing with a bit of cloth to remove any residues. Quote Link to comment Share on other sites More sharing options...
farmer_joe Posted February 27, 2016 Author Share Posted February 27, 2016 Cheers chaps, off for a look now. I know it's definitely not getting caught on any baffles, that was my first port of call! Quote Link to comment Share on other sites More sharing options...
western Posted February 27, 2016 Share Posted February 27, 2016 on back of the fuel gauge, make sure the metal U clamp is not touching any other metal parts --- gauge electrical connections, as it just shorts the gauge to earth. Quote Link to comment Share on other sites More sharing options...
farmer_joe Posted February 27, 2016 Author Share Posted February 27, 2016 Right, I tried your suggestion Tanuki and the sender wire(green with black trace) sent to a good earth gives a full tank. Black is obviously the earth and doesn't move the needle when sent to a good earth. And white is the fuel warning light. Out of interest with the sender out of the tank I connected up the wires and moved the float up and Down and it moves the need as it should, fuel warning light also comes on as well. Contact strips look ok, maybe we're a little dirty so cleaned them up, could possibly be a bit worn to but ultimately really didn't look bad at all. Also checked again that the float wasn't touching anything and it seeks that there I plenty of free space around the float bulb, though it does seem sat though it might be getting stuck. Any thoughts?! Quote Link to comment Share on other sites More sharing options...
farmer_joe Posted February 27, 2016 Author Share Posted February 27, 2016 Western, if the gauge shorts to Earth on the back what happens? No reading, always full? Quote Link to comment Share on other sites More sharing options...
farmer_joe Posted February 27, 2016 Author Share Posted February 27, 2016 I've also made up a temporary new earth with a good connection and hooked that up, won't know if that works until it goes below half a tank though!! Quote Link to comment Share on other sites More sharing options...
western Posted February 27, 2016 Share Posted February 27, 2016 Western, if the gauge shorts to Earth on the back what happens? No reading, always full? it'll either read full or pop the 12v feed fuse Quote Link to comment Share on other sites More sharing options...
Litch Posted February 27, 2016 Share Posted February 27, 2016 I occasionally get this but it is only when the top of the tank (i.e. where the contacts are) is very wet, usually just after I have given the underside one of my "special" cleans. Drying the contacts or giving them a quick squirt of WD40 always cures it. When I first bought the vehicle (some 16-years ago now) it caught me out once. Seeing that I still had half a tank it didn't click that the gauge had been reading that for the whole of the previous week. I was driving down the High Street where I live and it started to cough, it was at that moment that I realised what had happened so I immediately headed for our local filling station and coasted onto the forecourt just as the engine died! Quote Link to comment Share on other sites More sharing options...
farmer_joe Posted February 28, 2016 Author Share Posted February 28, 2016 So, today the fuel gauge is doing a merry dance back and forth from full to just under half! I've done 20 miles off a full tank. I don't recall it going clappers like that before but then I've paid it no real attention due to its miscreant behaviour. Is this a sign of an earth problem? If so it it the gauge, the sender or something else?! Quote Link to comment Share on other sites More sharing options...
Troll Hunter Posted June 8, 2016 Share Posted June 8, 2016 Sorry to pull up an old thread, but how was this problem finally resolved? What was causing the original problem with the gauge reading? Mike Quote Link to comment Share on other sites More sharing options...
sighnbox Posted June 8, 2016 Share Posted June 8, 2016 I had this exactly what you describe I to thought the float was getting stuck when I fitted a new tank just took the float out and bent it slightly until It reads correctly took 3 times/try s but now is perfect for full, empty, reserve etc Quote Link to comment Share on other sites More sharing options...
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