Miscellaneous Fuel Tank Questions

There are some rubbers for the three fixings, the front is just a bolt. The earth wire usually just goes under a scerw on the tank - any good earth will do!

Richard

You can see the correct fixings here, from the parts manual

Front mounts are standard nuts/bolts the rear single bolt fixing is a bit special, but can be achieved simply with a rubber bush, a longer bolt and a bit of jiggery-pokery.

It does earth through the tank, if you suspect a failing earth then a wire under one of the screws holding the sender in, run this back to a good earth location, there should be a suitable earthing point on top of the bulkhead somewhere. It is possible the sender is iffy, they do get erattic.

Alex

LR senders seem to have a special ability to work once you pull them out of the tank to test, yet they give up the minute they are screwed back in ;)

I had the one on my 101 out of the tank and moved it by hand and watched the gauge move. back in the tank and it always says empty!

From personal experience, I know that fuel tanks on 101's are *always* empty or nearly empty.

Alex

New tanks are available from our spares man though....

Steve

Doesnt matter how new the tank is, the V8 still sucks the petrol out of it at a phenomenal rate.

Alex

Seen that a few times on these Lucas gauge senders (not on a LR yet) The wire 'arm' of the gauge sender is bent into a 'C' shape to hold the plastic float and over time the sharp end of the 'C' makes a tiny hole in the float.

The clever bit is that the float fills completely with fuel and so looks empty even when it's full. On two occasions now I've managed to squeeze all the fuel out and repair the hole with a drop of epoxy resin - you can then fix the other end of the float to the arm.

Next time I'm going to drill two large holes in the float and squirt expanding PU foam in one end and see if that works. I've not found a separate supply of floats yet, you have to buy a complete new sender.

Julian.

hmmm. ill check for that! whenever i have had it out to test it the tank has actually been empty so i wouldnt be able to tell if the float was actually full

Whip it off the wire arm and 'bounce' it in the palm of your hand - you'll feel the weight of the thing then.

I was astonished when I found the problem, I'd have never believed that the float could become completely full of petrol, and always assumed that a punctured float (same applies to carb floats) would be partially full and the petrol would slosh around when shaken. With the Lucas floats, the (initially) white translucent plastic become yellow and more opaque with age thus further hiding the fact that it's full of petrol.

Julian.

It's rather obvious by weight without removing it from the arm if it's full of fuel, but there's always a few second hand ones knocking about at your local car or Landrover breakers, I've got at least three. I would imagine that the OP's problem is a bad tank earth to the chassis, possibly with painting to protect the tank.

Martin

it wouldnt be obvious if the tank was drained and had been sat empty for a while - even if the float did fill up, when sat in an empty tank it would surely drain again. This is how my tank has always been so i should take it out next time whilst the tank has some juice in.

Indeed, that was my original thought. But having spent sometime last night with my test meter I can report that there is a reasonable earth from the -ive terminal of the sender without the need for a separate cable.

The new piece of information I gleaned is that there is no apparent circuit between the +ive and -ive terminals of the sender. If the sender works (as I believe) as a variable resistor then I would have expected to be able to measure some resistance across the terminals. Either it is broken, greater than the 200k ohms my unit will measure or there is a school boy reason I cannot measure it in this way.

A further point that doesn't look quite right. The voltage between the +ive cable to the sender and the bulkhead (which I assume is earthed somehow) cycles between 5v - 11v on an approx 5sec interval. Voltage across the battery terminals is a healthy 14v. Should this be telling me something.

Many thanks to all for their contributions,

Peter

"Peter" wrote in message news:46090e8f$0$16303$ snipped-for-privacy@free.teranews.com...

There isn't a -ve or +ve terminal on the tank sender unit and there will be no apparent circuit between them as (assuming it's a diesel) it will have a low fuel warning terminal which is a simple switch which connects a warning lamp (blue) on the dash with the sender body and then to earth through the tank as the float nears the bottom of it's travel (or around 1/4 tank of fuel), and another terminal which connects the gauge to earth through a rheostat to the sender body then to the tank and ultimately to earth on the chassis. If the fuel tank itself is not earthed to the chassis there will be no direct connection between these terminals unless the fuel tank is almost empty and you may not notice this as the fuel gauge will barely read anything as the resistance of the tank sender unit to the gauge is at it's highest when the fuel is at it's lowest and 1/4 of a tank and above this connection will be broken. Assuming you have got two leads at the sender then earth them in turn and you will get either the blue warning lamp lighting up or the fuel gauge rising to the top, albeit slowly. If the vehicle is a petrol model then disconnect and insulate the one that lights the low fuel lamp. To check the sender connect your ohmmeter across either terminal in turn and the sender body, one will show open circuit fron full to 1/4 tank and no resistance from 1/4 tank to empty and the other will show low resistance in the full tank position and probably around 300 ohms or so when in the empty position. Oh, and *earth* the tank!

Hope that's clear. :-) Martin

Thank you.

Good news is that I now have a new fuel tank, a correctly working sender / gauge and a 175% increase in my understanding of car electrics.

Superb group full of excellent advice.

Peter

Unfortunately 175% of sod all is still sod all!

I suppose it could have been explained more clearly and simply but at least he can read and understand and has the ability to sort it, *and* appreciates the the help that is offered.

Martin

Jest Joshing!