For the Disco experts on petrol tanks

Classic disco V8, '92.

Fuel gauge at 1/4 tank (=20 Ltrs) the car starts to splutter and has no power. It will run, but chokes constantly with revs above idle. Contaminated petrol I'd say. But:

-Tried to clean tank with stuff you put in your petrol - no joy.
-Unscrew my petrol cap, to see if it was vacuum - no joy.

-Maybe its water, but that should :

a) slowly mix with petrol and get less. I've even shaken the car violently to see if I could mix it. - but no joy. Still the same after 18 months and

b) water is heavier than petrol, so with a full tank the problem should still be there but it isn't.

So with tank at any level higher than a quarter/20 Ltrs there is no problem. And it isn't a duff petrol gauge either, because I pump exactly 60 Ltrs to full every time. And my tank is 80 Ltrs.

I've been living with it for 18 months, because that's the easiest and cheapest solution.

But I still wonder what it could be.

Any idea ? :5bsifone:

Petrol pumps don't last forever, and yours will have to work harder and maybe suck air if the pump seals & bearings are worn and the fuel level is low.

Sounds like a classic worn out pump.

Peter

or a hole in the petrol pick up pipe 3/4 of the way down, soon as you get low on petrol it uncovers the hole and starts sucking air

Ah, good one guys. Thanks

Can I test/check the pump in any way to find out it is sucking air?

And just out of interest, what does the inside of a tank look like ? A standpipe, I would imagine, to leave sediment in the bottom (Can I drain that? don't think so). And how does the petrol gauge work. A float with a coil ?