Fuel tank and warning light

[Karl V]

SPOILER: this topic is quite dull...

So the fuel tank seems to be 52L (11 UK Gallons).

On the last 3 occasions, I've run the car until the fuel gauge says 0 (when on the level) and have only managed to squeeze 32L (7 UK Gallons).

I know the factory set the fuel warning 'with contingency', but this seems like 65% of capacity, leaving, in theory, 20L (4 UK Gallons) still in the tank.

Now I know that the fuel tank is triangular, so measuring by depth of fuel is tricky. I'm also not wanting to run the tank dry. But... If I'm 50 miles from home and switch to 'eco driving' (30 MPG), theory is I can get another 100 miles at least before sucking crap up from the bottom of the tank.

I also know that cornering and accelerating / braking sends the guage and warning lights crazy.

Just curious really how far into negative figures people have been 'in an emergency'. Theory says the guage could go to -20 before the engine starts to cough.

Asking for a friend

[phil4]

My bet would be that it's really 40L and so you can go to -8.

[smokin]

I put 10L in a dry tank and it wasn't enough to start. A couple of litres more and started no problem. The pickup, on mine at least, must be quite high

[Lighty]

I ran mine the other day till absolutely zero, & as you say it only took 40 litres to refil, so there must be a reasonable reserve.
Trouble is , when driving the damn thing is all over the shop, so you can’t really keep stopping to get a reading.
I just start looking for fuel when it’s on 10 .

[Karl V]

That would be interesting if a 52L tank reaches absolute 0 after 40L; and 10L isn't enough to start the engine.

So that means about 12L sloshing around at the bottom, but is largely unusable.

I guess one option would be to keep turning right (that seems to please the guage).

Thanks for the input. I won't try to cheat the system

[dc5ian]

i took out my fuel tank the other day to upgrade the fuel pump. There was some fuel left in the tank so we took the pipe of the fuel rail and stuck it in a petrol can to catch it, we then put 12 volts to the pump and watched it come out. as soon as it started to cough and splutter we stopped. After taking out the tank we poured the reaming fuel fuel into another Jerry can and was surprised to see about 12l of fuel.

[Karl V]

It's all adding up - thanks.

So a 52L tank is actually about 40L usable.

A warning light at 32L does actually mean 'you only have 30 miles of fuel left. Stop and fill up'.

Little and often I guess...

Good to know I have 12L of unusable fuel in case I need to empty the tank and fight zombies. Also good to know there is zero chance of sucking crap from the tank into the engine.

Thanks all for your insights.

[John Scherrer]

Not too sure about the new digital dash but the SPA dash fuel read outs can be reconfigured in the setup menus to change a lot of the things you're talking about.

Do a search on here .. A US member added a litre at a time and plotted a graph of fuel versus resistance of the sender - it was surprisingly linear and a bit of SPA dash tweaking made the gauge much more effective.

This includes the damping of the gauge too.

[Karl V]

Thanks John.

Not sure I'm ready to reconfigure anything just yet. Very happy though to know that 52 = 40. And 0 = 0. And 0 = -8. And empty = 12L (unusable).

By my calculations, low fuel means fill up, unless you want to siphon the tank and squirt zombies.

It's all very exciting!

[autobackup]

Having upgraded my Atom to the 2018 3.5R spec including changing from the SPA Dash to a Race technology Dash 2 all I can say is the fuel guage is absolutely spot on when it's full as it shows exactly 40 litres (an Atom, according to the manual, has a 40 litre fuel tank fitted) but as the fuel is used I can safely say that it's fuel tank readout accuracy rapidly becomes ever more woeful!

This week I drove it until the gauge showed circa 8 litres remaining (i.e. bouncing between 5 and 11 litres) and then topped it up to full - to my surprise it only took 14.7 litres!!

So it appears that in my Atom an averaged 8 litres indicated is in reality approximately 25 litres remaining in the tank!

One thing I would say though is that my upgraded Atom 3.5R is markedly more thirsty than in it's previous incarnation as a 3.5 310!

In the past (on the way back from the Ariel factory to Newbury after a service) I was desperate to refuel as the SPA was showing just a smidgin of a bar on the LCD readout - but was forced to continue as 3 petrol stations in a row on the A303 were out of fuel awaiting a tanker delivery - when I eventually found some fuel in Andover I actually put in 36 litres so my particular Atom was still running OK with 4 litres left in the tank!

[HenryJS]

I put 10L in a dry tank and it wasn't enough to start. A couple of litres more and started no problem. The pickup, on mine at least, must be quite high

10L is a little over the reserve level - this may be because if the tank was dry to start with - the 'swirl pot' around the fuel pump was empty and needed filling....

we ran our race car pretty much empty when doing some endurance racing, it was reading -5 and still running. but we Really REALLY don't recommend doing that. Running the car lean is a sure fire way to make it over heat and cause damage.

You can use all the tank - i dont know why your stopped with 12L in it dc5ian? we did the same thing here with the Nomad tank and got pretty much all 50L out of it?

[dc5ian]

it started coughing and spluttering thats we stopped. we was sucking out more air then fuel.

[HenryJS]

no idea sorry! does the new pump get all of the fuel up?

(is the new pump in the old housing?)

[dc5ian]

I will test the fuel pump once the engine is in and report back.


The new fuel pump replaces allof the old includig the fuel level sender which wasnt accurate anyway. I will worry about that at a later date. The new fuel pump also has a larger swirl pot and then it's incased with foam, so im expecting it to perform alot better.

Engine would of went back in today but we had to retap some of the engine mount threads as they were a bit tired

[HenryJS]

wasnt accurate anyway

no idea what youre talking about? they're great on the flat / in the garage / with the engine off? everywhere!