Gas Gauge Accuracy, Help please???

Happy New Year to you!!
I have had the same situation on my 360 prior 430 and new 430. Come to think of it, all my Lambo's (Diablo and Murcielago) all had the low fuel light come on when according to the capacities indicated over 5 galons left.

 

I often thought about running 40-70 miles past the low fuel light, but never did. I did not want to haul a plastic gas jug inside the car in case I ran out. The Lambo's were more conservative as I was lucky to get 18 gallons in the tank when the light came on.(26 gal tank) if my memory serves me correctly.

 

Yes - last chance and yes 5+/-. Happy new year to you as well!

 

On the other extreme, I had a Jeep Cherokee whose low fuel light came on and I ran out of gas within 5 miles. I'll take the more conservaive situation.

 

it's in the manual.

If the last segment G on the fuel level gauge
flashes and the second before last segment
H is on fi xed, it means that there are 18-20
litres (3.96–4.4 Imp.Gall.) of fuel left in the
tank.
When there are less than 9 litres
(1.98 Imp.Gall.) of fuel left, the symbol I
appears on the multi-function display and
the last segment of the gauge goes off.

 

The 430 has a 25.x gal tank.... 5.x gal of which is a RESERVE (this is when the light starts blinking).. so if you fill when it starts blinking, it is correct that it will take only about 20 gal to fill.

 

1.98 IMPERIAL gallon. As the fuel sender is pretty sensitive to even slight elevation front to back or side to side, I don't think there is any discrepancy.

 

again I don't understand why there is any confusion. flashing 1 bar on fuel guage means 1.98 imp gallons left. When fuel symbol first shows up on check engine status window, that means you 3.96-4.4 imp gallons left which is about 5 gallons. If you filling up when symbol shows up, that there is nothing wrong. page 34...

 

A couple of things to remember about the gas tanks on the Ferrari (I'm speaking about the 360 here, but I am guessing it's about the same situation on the 360).

First, there are two tanks and the sending unit is only in one. So if you park on a slant, and then start the car, you can get a false reading for a while, until the gas level between the two tanks evens out again.

On the 360, when the fuel light goes on, you have about 3.5 to 5 gallons left, which at around 12 miles to the gallon isn't all that much distance. So you better take that light seriously! If you continue to drive and ignore it, and the last bar starts flashing, you are probably dealing with around 2 gallons in the tank. And since the gauge/sending unit have a habit of being off a little here or there (and suddenly coming back into line), there is always a margin of error and/or surprise involved. Basically, when that last bar starts flashing, don't dilly dally around. Get to the gas station.

When I replaced the sending unit on my 360, I drove the car until the last bar started flashing. At that point, I went home and replaced the sending unit. When I got into the tank (as I recall) there was only about 3 inches of gas in the bottom of the tank. Not very much! Ever since then, when that light comes on and then that bar starts blinking, I make finding a gas station priority number one, since you are probably talking about 10 or 15 miles left.

In my SUV, when the gas tank light goes on, I don't pay all that much attention to it, since I think I still have a range of something like 60 miles left. But in the 360, it's a little more urgent when those lights come on. And when the last bar starts flashing, keep in mind there can be a slight margin of error too, which can leave you down as low as 1.8 gallons. For a Ferrari that's not much range.

Ray

 

It's because the angle of the sending unit arm relative to the bottom of the tank. When your tank is half full, the arm is about 45 degrees. So if gas sloshes around back there between the tanks, it may produce a change of 5 degrees or something in the arm - no big deal. But if the arm is down near the bottom and there is only a 10 or 15 degree angle left to the sending unit arm, then a shift of a small degree is larger relative to what's left. That's why things seem more accurate when you have a full tank or even half a tank. It's also why, when you are almost out, it can jump back and forth between showing almost nothing and a little bit left.

In other words, if your tape measure has a 3 inch +/- error, that doesn't make much difference when you are measuring a foot ball field, but when you are measuring your inseam for a new suit, it can have a real big impact on how the party goes! When the sending unit is measuring a full tank, a slight fluctuation isn't any big deal. But when the car is moving and it's trying to measure the last of the gas on the floor of the tank, that same little fluctuation can throw the reading all over the place much more quickly.

Ray

 

I think that fuel warnings are not just a matter of gallons. Rather, the primary concern is sufficient warning so one can get to a gas station. Assuming that one is on the highway, a warning at 5 gallons and 15 - 17 MPG, will allow 75 - 85 miles of travel. My wife's Vibe has a warning light that comes on with 3 gallons remaining. Given her MPG, she has about 96 miles of travel remaining. That is similar to the miles remaining of your Fcar.

 

I forgot I had a 430 manual in PDF. Here is the page that shows how the fuel gauge works on the 430. It's exactly opposite from the 360's method.

I think what would be most helpful to this thread is if other 430 owners could chime in and explain how their cars operate with regard to the indications on the dash as fuel gets down below 5 gallons and 2 gallons. That would help answer the original question as to whether there is a problem or if the manual is off.

Ray
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The fuel gauge in my 360 reads slightly higher upon startup, and lowers within minutes. There was one time when it showed 2 bars on startup and I drove away without filling up, but after getting on the highway, the warning light started blinking. I drove about 10 miles before reaching a gas station, so there was only maybe 1 gallon remaining.

 

Darn!! you would almost think that they provide those owners manuals with the car for a reason.