Talk to me re Petrol Tank gauges

[Carslil Jim]

I have a LR tank installed and the original guage on the dash.

It has worked up till now, but in strange ways. Eg when the guage gets to half it suddenly drops to empty. I live with that but now I have a different problem.

I filled the tank (wasn't cheap either) and the guage dropped to zero...and stayed there. It has done the zero drop on filling before but it recovers and shows "full" again after a few ks. This time I have done a 100 clicks but she still shows empty.

I would welcome suggestions from cheap to expensive!

[JDNSW]

Best guess is a wiring problem. The most common problems are poor earths, either at the tank or at the gauge, so these are what I would look for first (after checking the relevant fuse).

A test you can carry out is to disconnect the wire to the tank sender unit, and observe teh readings with it disconnected and shorted to earth. Readings of empty and full suggest the problem is at the tank, and this will be either a faulty earth or the sender unit. This can be removed from the tank (but not with it full!) and tested with a meter - I can't remember the resistance range it should have, but someone will come up with it. At this stage check that the float moves freely and is not punctured.

If the first test does not show on the gauge, change your focus to the instrument panel.

John

[Bearman]

As JD said most likely earth problem.

[Carslil Jim]

Thanks for the earth tip. I went chasing wiring but it looks like the guage is in the top of the tank which is very close to the back floor so I cant see or get my fingures in there.

That means I will have to drop the tank and frankly I am terrified of fiddling with a potential bomb. Do you have any advice on how I should go about getting the tank down please?

[JDNSW]

Probably someone will be able to help more if we knew which model Landrover we are talking about!

John

[Carslil Jim]

Sorry John,

Its an 85 County V8. The only one in the country with a "hatch" tailgate!

The petrol tank is a long range tank from that era. It holds 120 litres.

[JDNSW]

Sorry John,

Its an 85 County V8. The only one in the country with a "hatch" tailgate!

The petrol tank is a long range tank from that era. It holds 120 litres.

Non-standard tank makes it a bit difficult to advise (the standard tank has the sender in the LH side). You may be able to see the wiring from one of the wheel arches, and possibly even reach it. If not, there will be little alternative to dropping the tank.

You should run it as low as you are game before doing so, simply to make it easier to handle. It is probably attached by the same bolts as the original tank, and can be lowered by a floor jack, probably disconnecting the fuel pipe(s) as it is lowered. You may have to remove the sway bar (if fitted) and possibly part of the exhaust. The "bomb" aspect is very unlikely provided you avoid spilling a lot of petrol (tape up or plug hose points (both ends) as soon as you disconnect them) and avoid sparks - disconnect battery before starting work, care with leadlights, power tools etc.

An alternative that some have used is to cut a hatch in the floor of the tub to get at the sender. Just make sure you measure right and get it in the right place. And do a neat job, and think beforehand about how you will cover it, and remember there are ribs under the floor you really don't want to cut.
Hope this helps

John

[VladTepes]

I have a similar problem. I have a switch which is supposed to switch the guage between reading main and aux tanks. But whenver switched to read the auxilliary, it shows empty.

I hate the switch idea anyway so am going to get another fuel gauge and hook it up direct and work from there.

Anyone know where I can get a standard Defender (Tdi) fuel gauge? 2nd hand is fine.

[Carslil Jim]

John,
Thanks for the advice. I had not thought of peering thru the wheel arches so I will take a peek and see what I can see.

In the meantime I have calculated that roughly I get 500ks for 100 litres so I will have 20 litres left after filling it up. When the oddometer hits 717, I must find juice!

I will let you know what happens if there is no explosion.

[Carslil Jim]

I am embarrassed to say that when I looked under the LH wheel arch I found the tank sender unit installed high on the side of the tank and quite accessible.

On the principle of "first do no harm" I wiggled the electrical connections to the fuel tank. That made no difference.

Then I pounded the side of the tank with a rubber mallet...not too hard, and that made no differece. My guage still red empty and the warning light was on.

I swore loudly and gave up in disgust and decided when the petrol level was lower I would haul the sender unit out and wiggle the float around.

But, Lo! I went to use the LR this morning and the guage was working and the warning light was out.

I think I will still pull the sender unit and have a squizz at it when I burn off some more juice.

[rick130]

I have a similar problem. I have a switch which is supposed to switch the guage between reading main and aux tanks. But whenver switched to read the auxilliary, it shows empty.

I hate the switch idea anyway so am going to get another fuel gauge and hook it up direct and work from there.

Anyone know where I can get a standard Defender (Tdi) fuel gauge? 2nd hand is fine.

Vlad, mine does the same.

Many years ago I pulled the sender out, checked it, checked the output readings (all fine) and re-installed.

Still didn't bloody well work and I hate tracing wiring so didn't.

It still doesn't read but at least the empty light comes on and the pump stops when it's all out.

[Loubrey]

Defender fuel tank sender units are not that bullet proof either and it's not a complete impossibility that it needs replacing. In fact if it's not earthing it is most unlikely that it's the guage that's faulty. I've had to replace a sender before, luckily on a TDi 90 with access under the driver seat.

Rimmer Bros will most probably be able to help you out as per the link below. Remember we look at the "Ex VAT" price. They don't weigh much, so parcel service should be cheap enough.

Unfortunately you'll have to spot your particular one in an uncomfortably long list. Just remember to order the gasket as well!

90-110 & Defender Fuel Level Sender at www.rimmerbros.co.uk (http://www.rimmerbros.co.uk/Item--i-GRID010440)