tim hunt Posted September 30, 2016 Report Share Posted September 30, 2016 I have always known my fuel gauge to be pessimistic and know I can drive a really good distance after the needle has reached E. The most I have ever been able to get in when brimming the tank was 48.75 litres many years ago - the gauge had been on E for ages, I wasn't too bothered on that occasion since I had 10 litres in an approved can in the boot. The handbook figure for capacity is 11.75 imperial gallons or 53.5 litres (actually closer to 53.4 litres if the gallon figure is correct) if this handbook figure is right this suggests that when the tank took 48.75 litres I should still have had over a gallon left. My tank is original, just out of interest has anyone had the experience of filling one from completely empty and if so what did it take? Tim Quote Link to post Share on other sites
stuart Posted September 30, 2016 Report Share Posted September 30, 2016 Not entirely sure as I try not to let them go that low but I can get over £60 worth in sometimes! At roughly £1.18 ltr Stuart. Quote Link to post Share on other sites
MichaelH Posted September 30, 2016 Report Share Posted September 30, 2016 (edited) I have been trying to see what MPG my car would do so I ran the tank to less than empty and then filled it up - 45 litres went in which equates to 10 gallons Michael ps £60 at 1.18p /litre =50 litres=11.18 gallons seems a large tank? Edited September 30, 2016 by MichaelH Quote Link to post Share on other sites
MichaelH Posted September 30, 2016 Report Share Posted September 30, 2016 Filled my tank with 45 liters as above and was down to 1/2 full after 23 miles a bit alarmed but couldn't smell petrol checked the connections and found that I had lost the earth to the petrol tank sender reconnecting it made a big difference I wonder if there is any variation in the size of tanks? any body know? Michael Quote Link to post Share on other sites
tim hunt Posted September 30, 2016 Author Report Share Posted September 30, 2016 Michael, your tank took ten gallons to fill when treading below "E". This parallels my experience. You have no way of knowing how much fuel was left in the tank, it might even have been a gallon and three quarters which would give a capacity in line with the handbook figure. It has occurred to me that it might be wise to change a short length of rubber hose in my system for R9 spec. This will entail running the tank low and then completely draining it so I will then be able to answer my own question! I will report back in due course. Tim Quote Link to post Share on other sites
MichaelH Posted October 5, 2016 Report Share Posted October 5, 2016 Just had an idea! If the fuel gauge doesn't relate to the the level in the tank - i.e. there is still a gallon in the tank when it shows empty Then the float inside the tank obviously doesn't do down far enough to measure the lower levels of fuel in the tank what we need is to see how far it goes down and if necessary extend it so that when it is down the tank is empty and the gauge will accurately reflect the fuel left Any body done the work already? or looked at the sender unit and whether it reaches the bottom of the tank? Michael H (thinks: do I have a spare tank somewhere that I can take to pieces to check?) Quote Link to post Share on other sites
Lebro Posted October 5, 2016 Report Share Posted October 5, 2016 I would suggest that it is more likely that the gauge & sender are not correctly calibrated. This done by moving by small amounts the coils inside the gauge (if it is the older type where the gauge instantly jumps up to it reading when ign is turned on) If it is the later type then I would check the voltage stabaliser ( does the temperature gauge read correctly? 'cos it also uses the stabiliser) The idea that the float does not reach the base of the tank could only happen if the wrong sender is fitted, or if someone has fiddled with the end stops on the sender. Why not peer into the tank filler with a torch (not a match !!) and using a piece of stiff wire push the float down to see how far it can go. Bob. Quote Link to post Share on other sites
MichaelH Posted October 5, 2016 Report Share Posted October 5, 2016 Answer: When I got an old tank out and looked at the sender its arm was limited in movement by two stops. When on the lower stop the float was still well clear of the bottom of the tank By straightening the wire it was possible to get the float down onto the welded flange at the bottom of the tank So it should then show a more accurate indication of the "E" for empty Of course now I am back at the keyboard I forgot to check that the now extended arm does not meet the internal boxing in the tank (it usually take me at least three times to do anything- so) I will go and look at that detail perhaps tomorrow. MichaelH Quote Link to post Share on other sites
MikeF Posted October 6, 2016 Report Share Posted October 6, 2016 Well I confess to a most unmanly thing - I RTFM. Per that the capacity of the tank is 11 3/4 gallons (14 US, 53.5L). On my car the usable capacity is slightly less than that as I have left the fuel feed pipe standing about an inch proud. of the tank floor. (it does a bit on all cars I imagine. The idea being to try not to suck up any debris floating about down there. I then fiddled with the sliders in the fuel gauge and using a dipstick and a bit of string on the float to calibrate I got the gauge to indicate the new empty and a 1/4 as accurately as I could and 1/2 and full pretty well. Driving the car about shows that its accurate enough. The biggest inaccuracy is the poor earthing on the voltage limiter. I haven't had an unplanned use of my 5L can anyway... Mike Quote Link to post Share on other sites
TorontoTim Posted October 6, 2016 Report Share Posted October 6, 2016 On a slight(?) tangent: does anyone know the voltage or current or whatever it is we measure at both full and empty for a standard TR4 gauge? Quote Link to post Share on other sites
stuart Posted October 6, 2016 Report Share Posted October 6, 2016 Its ohms resistance FWIW But I cant remember the values offhand.It is normally low at full and high at empty. Stuart. Quote Link to post Share on other sites
RobH Posted October 7, 2016 Report Share Posted October 7, 2016 There is some very useful gen on this website: http://mgaguru.com/mgtech/electric/fg_01.htm Though its for the MGA the technical details won't be that much different. Quote Link to post Share on other sites
MichaelH Posted October 9, 2016 Report Share Posted October 9, 2016 Took my tank out and found that the float had a rubber ring round it, to stop the float touching the bottom of the tank? Emptying the tank I got 7.5 litres + approx 11/2 gallons of petrol out (indicated empty) I bent the wire so that the rubber band rested on the floor of the tank Put it all together and added petrol It still needed a gallon+ to move the needle off "Empty" the last 1/2 gallon moved the needle to just less than empty Not much further ahead really! MichaelH Quote Link to post Share on other sites
MichaelH Posted October 10, 2016 Report Share Posted October 10, 2016 Finally ran out of fuel with 264 miles on the clock I am disappointed that it didnt go further just diriving round short journeys and a few trips up to mother (94) 30 miles up the A50 (70mph) MichaelH Quote Link to post Share on other sites
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