456 GT Fuel level sender replacement

OK, thought that I would post on replacing the fuel lever sender, that resides in the tank. This applies to a 1994 euro spec GT, the M's may well be different.

Over the spring and summer this year I have noticed that the fuel gauge would intermittantly drop to 0 or be stuck on full so I Thought that this autumn I would look at fixing it, as it is a PITA it not working properly.

The sender is the middle of the tank and is held in by a ring nut, firstly, there are no new units available in the UK and it is on back order from Italy, so a new replacement unit was not available!!! I had to either use a used one or a generic unit which is available from Maranello Connsainarries in Egham. I choose to fit the generic unit from Maranellos, they were very helpful and the unit arrived the next day. They're did warn me that the generic unit would need modifying to fit then456 !!!!' So on to the install!!!

The tank is behind a fibreglass panel in the boot, firstly remove the spare wheel tray lid, then remove the carpet trim over the radio/amp. Then remove the carpet board that covers the back of the boot, this is held on by three self tapers at the top of the carpet. Once this is out you should see the tank cover, this is held on by 10mm bolts around its edge, remove ,these together with the brackets for the carpet trim at the top and the spare wheel tray cover rail at the bottom.

See pic below of tank with sender.
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To un do the ring nut I fabricated a spanner from a piece of 15 mm tube and a u bolt used for a TV arial bracket, see pic
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Once you have the sender out of the tank you will need to make up a template from card and mark out the sweep of the old float so that the new generic one mirrors this movement, old sender and ring nut below,
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After a lot of mucking about and trail and error I discovered that the new generic sender had a smaller mount plate so would not have fitted properly into the tank and may move once fitted, it also did not have a superseal socket on it, but just three Lucar spade connectors, so I decided to use the old sender mounting and fit the new wiper/float to it. I had to get the new riostat/wiper of the new unit by hack sawing the plate from the tube mount, see below pic of new sender,
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I riveted the new sender wiper/float unit to the old mount plate, used the card template to get the float positions at full and empty as close to the original, then I had to work out the wiring!!! what a nightmare !!!! The loom connection is a 3 pin superseal type but only has two cables in it, a purple and a black. The new unit has two tracks, one seems to be for the level whilst the other switches the low fuel light on, I ended up with the white wire connected to the purple in the loom and the pink connected to the 3rd un wired pin????? the black wire in the loom was connected to the pivot wiper at the sender unit. Not sure how this works but it does!!!

See pic of old mount with new wiper/float
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Not sure why the last pic is upside down?? I will post more pics of the tank cover and boot carpet trim when I get that back in. I have just taken the car out today and filled up the tank, the gauge shows full !!! Just have to wait to see what happens as the fuel is used up and whether the gauge works OK. At least it will not take too long to get to empty as its a V12!!!!

 

Just to add, that I refitted the sender using the old gasket, which looked OK. I put a small bead of black silicone sealer on it just to be sure that it would not leak, so far all seems good.

 

Just put the fibreglass cover back on today. Not an easy job, you have to put it back, top first and then push the bottom of the cover towards the front of the car, forcing it over the carpet in the boot-a right pita!!! I managed to get it back in without removing the audio mount tray, although I think if you can be bothered, then taking out the audio tray would help a little.

Also check all the cap nuts on the tank frame that the cover bolts to, before you refit it as once it was refitted I found two of the bottom bolts would not pick up, so suspect that cap nuts behind have moved or broken- they are very weak and cheap. I will leave the two bolts off until I next need to access the tank, probably for fuel pumps!!! If anyone thinks that I should put these two bolts on ( i cant see that they do much other than hold the cover on) then let me know. I will post a pic of the tank cover later.