fuel Guage error?

Mine has been reading 3/4 when it is full. I have a 36 gallon tank that fills to 30 gallons. By re-fueling at various points along the gauge, I have learned what each means: 3/4 - full; 1/2 - 2/3; empty line - 1/3. I now fill as soon as I hit the empty line (needing 20 gallons). Both my tanks (same size) were reading the same way.

This last fill up (on both tanks), I noticed they only fill to the 1/2 mark. So, I'm going to re-test the points on my next long trip. It could have been the nozzles at the station where I filled up. It could be something else.

The sending unit can go bad. Also the old floats (not sure on new ones) were actually made of styrofoam/foam and after years will start to absorb the fuel. This makes them heavier, so they become mis-calibrated.

X2. PaPappy. Only thing I would add is when you fill up RESET your trip odometer or write the millage down. My RV goes >400 miles on a tank of fuel. When I have traveled 350 miles I start looking for cheap diesel. This has worked for me for 14 years and as a pilot we say the two most usless things are a runway behind you, and air in the fuel tank. How true!

To change the fuel sending unit, you have to drop the fuel tank. Nothing easy about that. Look at the fuel vent hose. It probably has a sag in it and is full of fuel and not venting properly. Easy fix.

Richard

We had an earlier model of the Chieftain back in the 90's & the only way to fill the fuel tank was as slowly as possible, otherwise it would trigger the auto shutoff on the pump. Not their best design feature in my book.... :(

Mike,

There is a line in the FAA student pilots manual that I have always liked, it says the only time to believe a fuel gauge is when it shows empty.

There is a issue with many RVs. The tank placement makes fueling difficult. And now, with the high foaming gasahol (aka motorfuel) things are we worse than we ever expected. A fuel delivery nozzle detects full by using the passing stream to suck in air. When anything interferes with that air flow, it trips. So, the foam will get you. This makes fueling a flat tank to full very problematic. And worse yet, some pumps are more sensitive than others.

Then there is another problem. The hardware produced in those days was not as alcohol proof as they had hoped. There is no reason to trust the gauge reading as the calibration could easily be bad.

My solution? Know your coach.
This is easier than it sounds. Write the odometer reading on every fuel slip. (Yes, you have to push the "I want a receipt button.") Use the spreadsheet in you laptop to keep a running fuel average. When the last fill would say you were getting 20 MPG, you know it was a bad fill. Just stop a little sooner next time.

Matt

I have a 2004 Minnie and have it shut off pumping too early. I am able to get another 5 gallons of gas into the tank after the first clink off. What I have done it use my scan gauge and see how many gallons of fuel I have actually used and refill it to that amount. It's a few gallon shy of actually being topped off.
I can't tell if yours is on a Ford or Chevy chassis, but the Scan gauge has a tranny temperature function. Well worth the investment. Hooks up to the OBD and reads the computer. Under TANK function, you'll get the MGP, miles driven, miles left in tank, gallons used and gallons left.
Here's the link Scan gauge

The pump shutoffs are based on pressure at the pump nozzle. If there's some problem with the fuel filler hose or the vent line from the tank, it can cause the pump to shut off early. (Think along the lines of kinked or blocked hoses, sags or routing that cause low points where liquid collects, and so forth.)

Sometimes when its marginal you can get more accurate filling by pumping at a less vigorous rate.

There is a fuel level sensor in the tank that sends a signal to the fuel gage. The sensor is easily changed without removing the tank. Typically it is mounted rough the top of the tank. There is a float which is attached to the end of an arm. The float moves up and down which causes the arm to move a slide wire resistor. Long story short, the slide wire occasionally goes bad and needs changed. Climb under the coach and see if you have access to the top of the tank. The sensor will be a round plate, screwed to the top. There will be a single wire attached to a screw in the center. It is a simole "remove and replace" but you will need to contact the factory for the correct part or you will have to pull it out and take it to a truck parts store

I don't know about that Winnie, but some of the MHs have issues with the fuel getting down into the tank, and will shut off the trigger well before the tank is full. While it may not always be a good idea to play with the trigger to get as much into the tank as possible, you may want to fiddle with it at least once, to see what "FULL" actually is on this rig.
Once you know, I would then figure 7 mpg, and calculate the use based on mileage...say fill up when you have gone about 300 miles (42 gallons), which should give you plenty of "spare fuel", and you can try and figure from there.

I have a faulty gauge in my car, and I've gotten to where I don't really trust it, so base my use on miles. Just make sure to give yourself enough extra so you don't end up on the side of the road (like I did once).

Also...double check on that fuel tank capacity....it may be wrong?

good luck and Happy Camping