Can anyone explain to me why according to my fuel gage, I get 115miles to the first quarter of a tank and 70 on the second quarter and so on?

 

I'd like to know this myself. I shared the same sentiment until mine started giving me gas when I stomped the floor.

Maybe it's your gauage going out - I've got the suspicion that mine is but, then again, mine has ALWAYS done that.

 

Most every Ford truck I have ever owned has done this. Relax, its become a normal thing....

 

There way of making you think your really getting good mpg the first 120 mile you drive it... Mine does it also.. has since 1997 135,000 miles ago

 

It's not a mystery. It's just the way it is. I've owned 4 Fords (2 Trucks, 2 Cars) in the past 5 years and they all did the same thing.

 

My personal theory iis that if you look at the gas tank, the geometry of it is such that it has a higher volume at the top than the bottom. It's not an exact cube--- the sides are not straight up & down and it is curved where the bottom meets the sides-- so there is more fuel in the top 'half' of the tank than the bottom "half." Since the float only measures the level of gas, not the volume, it would give that effect.

I did not test this and don't know it for a fact, that's just a theory. I have noticed this in practically all cars I have ever driven.

 

I've lived with it so far, just annoys the snot out of me. Thanks for the posts. At least I am not alone.

 

Another thing to remember is that you are bound to have some gas in the filler tube, which is above the float level. It will not start going down until the level of the gas gets to and below the float.

 

Mine does it and every vehicle i have ever driven has done it

 

Mine does it too, however when it says empty you usually have a few gallons left. I find that when I fill up at half full it takes about 47 litres to fill which is half of a tank.

I consider the guage fairly accurate its just that you can drive on full and on empty for a while without the guage moving much.

 

Used to drive a Chevy work truck. Thing would go days with the guage on full. Would slowly drop to 1/2. From 1/2 tank on you had better be looking for a station! It's impossible to build a guage that is any more accurate than what we have. Like Clifford said, the shape makes it difficult to improve on a guage. I like my Scanguage. Tells me how many gallons I have used, and how many are left. It will even show the gallons per hour while moving. Everytime I have filled up, it is within a gallon. I also know that when my low fuel light comes on I have approximately 5 gallons remaining.

 

It has to do mainly with the shape of the float arm... the float arm moves in a non-linear response to the fluid level. If you divide the tank level into quarters, the float arm moves more in the last quarter than it does in the first quarter.

The only way to change this would be to go to a linear float (i.e. one that moves straight up and down like a modern toilet tank float). The problem with that design is that the float tends to get stuck on the guide rod if any contamination builds up in between them.

Personally, I'd like to see them go to a non-contact ultrasonic level sensor. No moving parts to fail and (when averaged out over a certain time period to minimize the effects of sloshing) accurate, linear responses to changes in tank levels. (and it'll keep the mosquitos and mice away!!) Marginally more expensive, but not much IMHO.

-Joe

 

There are som esmart people in here! Thats alot more knoledge than I expected but makes perfect sense. I wounder if any Ford people ever asked this question to their engineers?

 

I only use my gas gauge for a quick situational glance if I haven't driven the truck for a few days.

I always fill up and everytime I fill up I hit the Reset on the trip meter.
Much more accurate than trying to rely on the gas gauge.
My Low-Fuel light comes on around 325.
If it is convienent, I may refuel around 300 otherwise, the Light will remind me. Also, I usually know where I'm going, what the roundtrip distance will be and some quick mental math will tell me if the trip will require a refuel. I wouldn't dare try that with the gas gauge.

At 360, nothing else is more important than finding the nearest station.
I have never put any faith in the gas gauge, it's really unimportant and practically unnecessary.

Of course, if someone else may use/fuel your truck this system doesn't work.
I try to get my wife hit the reset when she buys gas for her van but, it isn't a priority with her. I am stuck depending on her faulty (Ford)gas gauge because the trip meter usually says 885 miles or something ridiculous like 47.

 

All of the reasons thrown togather give the final result.
In addition, the dash has a processor that does not react instantly at driving the visual gauge position but is on a timed basis. The level has to change enough to cause the processor to update the gauge position.
Then throw in any fault with the float sensor and you get all kinds of end result as the level changes.
The float sensor is usually segmented. If a segment is defective the level can be accurate at some points and not at others.
This is a way to keep the gauge circuit indicating over the long term even though it may not be correct instead, of going without any indication at all.