Mystery fuel

Can anyone tell me the mystery to actually finding the correct fuel tank consumption? I fill the car up, and it shows 3/4 tank. Then its on empty for a good 50 miles. I feel that I can't take the car on a road trip because I can't judge the mileage. I have the standard 8(?) gallon tank, but this knowledge seems useless. Please advise!

There have been several threads here about this problem....They involve bending the float arm and/or re calibrating the sensor coil...See the knowledge section of this site for a possible cure...

When my sender went wacky i just put a paint stick in he trunk and checked it every 150 miles or so It worked out thats about how long before you want to stop for a break anyway to streach your legs if not sooner.

I'll second that Barry....

I reset the trip odometer on my car with every fill up. I have a speedo in KPM's so I drive it 225 km's and then fill it up. I have put in a s little as 5.6 gals and as much as 7.3 gallons, so the right foot does make a big difference in my car...and yes, my mileage stinks, runs from 17 to 26 mpg after doing the km to miles conversion....not an economy champ, not intended to be either....

I had a wacky AutoMeter fuel sending unit out of the box. I took the sending unit apart, whittled down the float with a belt sander and put it back in. Worked like a champ.
Your consistent 3/4 reading migh be because of the unit's placement in the tank itself. If it's near the top of the tank, there might be an air bubble in the top quarter -- depends on the angle of the tank and the unit's float in relation to it.
Mine was an easy fix.

Jeremy,

Forget the fuel gauge.

Try this:
Fill your tank and re-set the trip meter.
Drive about 100 miles
Fill the tank and note the number of gallons it took to fill the tank.
Note the number of miles on the trip meter, and re-set it.
Then divide the number of miles that were on the trip meter by the number of gallons it took to fill the tank: Average Miles Per Gallon.
Multiply the MPG times 8 (8 Gallon tank) this is the potential distance you can drive before running out of fuel.
Every time you fill the tank you can do a quick re-calculation before you re-set the trip meter.

I average about 20 MPG, and I have an 8 gallon tank in my VS, so I figure that I can go about 160 miles before I run out of gas. So, when my trip meter reads 140, I fill it up.

I have driven my Harley all over the Western US without a gas gauge using this method.
Don

Or, you can remove the sender from within the fuel tank, take some of the bend out of the "kink" between the sending unit and the float, replace the unit and, with a full tank, see where the gauge rests. If it isn't a needle's width above full or 4/4'ths, then remove and try re-bending until you get it right for full.

Once THAT end is done, you can either try fine-tuning it for "empty" or just run it down to "R" and then re-fill the tank, note how many gallons it takes to do so and THAT should tell you how much is left when you get to "R" as your "reserve" before you run out.

Makes the paint stick dip stick sound pretty easy, doesn't it?

gn

Have a "Merry"!

Remember, you want the gauge to read accurately over the LAST HALF of the tank, rather than over the first half! Use the trip odometer for a reference, if you have one.