Motorhome fuel gauges

TEO · 02-02-2008, 07:18 PM

What's with the fuel gauges in motorhomes?
I had an '88 Southwind for a number of years and the gauge baffled me. After filling up, the needle would be pegged on full until I put over a hundred miles on it. By trial and error, I found that I still had a lot of mileage left when the gauge read "Empty", so I got in the habit of refueling at least every 400 miles. Then I had a Safari, where the needel would stay on "Full" until I drove over 300 miles. Unlike the Southwind, when the gauge said "Empty" it really was empty and I don't want to discuss how I found that out.

Now I have the new (to me) 2002 Journey. The dealer "Claimed" that all fluids were full, but you never know. This week we ran it to the point where it was down to 3/4 full. I wondered how full it really was from the dealer so I filled up this morning. It took 22 gallons of diesel and I can assure you that when I was done it was really full. Can this be right? Can the fuel gauge really be accurate? Amazing!!!

Paul

TEO · 02-02-2008, 07:18 PM

What's with the fuel gauges in motorhomes?
I had an '88 Southwind for a number of years and the gauge baffled me. After filling up, the needle would be pegged on full until I put over a hundred miles on it. By trial and error, I found that I still had a lot of mileage left when the gauge read "Empty", so I got in the habit of refueling at least every 400 miles. Then I had a Safari, where the needel would stay on "Full" until I drove over 300 miles. Unlike the Southwind, when the gauge said "Empty" it really was empty and I don't want to discuss how I found that out.

Now I have the new (to me) 2002 Journey. The dealer "Claimed" that all fluids were full, but you never know. This week we ran it to the point where it was down to 3/4 full. I wondered how full it really was from the dealer so I filled up this morning. It took 22 gallons of diesel and I can assure you that when I was done it was really full. Can this be right? Can the fuel gauge really be accurate? Amazing!!!

Paul

Dick A · 02-02-2008, 09:09 PM

Paul, If you had ever had the dubius enjoyment

of changing an in-tank fuel pump and fuel guage I think you would better understand why the gauges are not accurate.

The gauge on my current Ford F-32 chasssis is no different. The problem is the swing of the float arm is less than the height of the fuel tank. On the F-53 the upper travel is at least an inch below the top of the tank and the lower travel is somewhat above the bottom of the tank.

Thus, the gauge will indicate full until the gas level starts dropping below the float level. Also, there may be usable fuel left when the guage shows empty.

I tend to watch my trip odometer and I usually fill the tank at about half empty.

flashajt · 02-03-2008, 03:02 AM

Our Journey gets us all the time too. Cruising down the road with genset running, about 450 miles into a trip, genset cuts off. Guage shows just under 1/2 tank but its really at 1/4 tank. Takes 65 gallons (95 gallon tank) so guage is really inaccurate.

Now I try to watch miles driven vs. the guage so that our genny doesnt cut off if we are using it.

ichn2go · 02-03-2008, 03:36 AM

Gas guages, even on autos are mysterious things.
A report was on TV recently that the reporter drove over 40 miles after the guage said empty.
As a general rule , when the guage says a quarter of a tank I start looking. Sooner if I find a decent station.

You did the right thing by checking. Now do it at 1/2 an 1/4 then you get a good idea of what your guage is doing ..Tank size + the # of gallaons at each mark should tell you something about your guage. All things being equal your first measurement at 3/4 = 22 gallons times 4( you filled up 1/4 of the tank) = 88 gallon capacity..so if you have a larger tank, something is not quite right..check it at the other levels...Good Safe Miles

Petro · 02-03-2008, 07:35 AM

My gage does not move of the full mark until I have traveled about 100 miles. I have some reserve after it gets close to empty. How much I really don't know because I have never ran out of gas and don't want to. I start looking for fuel after 400 miles since fill up.

Don

Izzyblueye · 02-03-2008, 08:06 AM

One thing I have always been very happy about on my Itasca, is the fuel gauge is extremely accurate. It is a F-53 and has been checked numerous times for peace of mind. My Dad always told me there is one fool responsible for running out of fuel and that is fool in charge of the fuel gauge.

smlranger · 02-03-2008, 08:34 AM

Teo,

I think we've all had to figure out the particular behavior of our fuel guages. Our's behaves similar to Petro....doesn't move off Full until we've traveled 100 miles or so. At 1/2, it seems to be spot on (I can squeeze about 42 gallons in at that reading). When gets near the E and I get the 'low fuel' warning light on the dash, I still have 25 - 30 gallons left in the tank.

I usually plan to fill up when the beast gets between 1/2 and 1/4, but have run with the 'low fuel' light on for 50 miles or so and never had a problem (not running genset at that point).

bruceh · 02-03-2008, 08:47 AM

At least these are consistent behavior that you can learn to cope with. Many years ago, I had a car that would occasionally run out of gas showing about 1/8th of tank. Most times, it would run normally down to empty.

I got so paranoid that I pulled the gas tank to replace the sensor and heard this funny clunk sound as I moved the tank. When I pulled the sensor, I could see a piece of hose in the bottom of the tank. Someone had apparently siphoned gas from my tank and broke off part of the hose. It would sometimes wedge under the sensor giving me a false reading.

McDuff · 02-05-2008, 11:52 AM

I burn between 20-25 gal before my needle moves off full, in a 100gal tank. I've run it down to just under 1/8(warning bell came on) and didn't run out.

Weird thing compared to most other people, my generator was happily humming away the whole time. Wonder when it would quit, when I am out of gas?

Moder2 · 02-05-2008, 01:54 PM

One of the first things they teach your in truck school....

Never trust your fuel gauge. Know your MPG, and How many miles you have gone since last fill up.

John

FenceMan · 02-06-2008, 12:11 PM

my 2003 ultimate freedom has a 100 gal. diesel tank -- gauge goes down real slow for first 1/2 tank --- then goes down pretty fast from 1/2 to empty--- I watch my miles traveled more than my gauge -- it is too bad that all gauges are not 100% right !!! Let's see---how much water is in your gray tank??? ha...ha... gurgle...gurgle

hamguy · 02-07-2008, 10:32 AM

I judge my mileage by watching the movement. I ALWAYS fill the tank as best I can. Variables are the slope/tilt of the RV when filling.

I can often get 125 miles on the tank before the needle drops to the "F" indicator. At that mileage, I am running about 7.5+ MPG. Subsequent indicators are about 25 miles per 'tick' mark on the gauge.

This decreases slightly as the gauge drops to where I should be at about 350 miles at the 1/4 mark. IOW, on good mileage runs, I can get to almost 400 miles at the 1/4 tank indicator. Typical is 325-350 miles, however.

A couple weeks ago I drove to Quartzsite. I had a full tank at first and when I pulled into the camp, I had about 160 miles. I thought something was wrong with the gauge. It was still nearly pinned.

Anyway, I ran the generator at the camp for about 29 hours and filled again. Figuring 0.53 gal/hr for the gene left me with 8.3+ MPG for the rig.

After filling on our return, I got 6.77 MPG. I can only believe I didn't fill completely in Q.

In any event, these generalities yield a reasonable way to estimate mileage and how to interpret gas gauge readings.

BTW, I can guess MPG numbers by watching wind, hills, speed, etc. Over the 4+ years and 45,000 miles I have driven the rig, the mileage has varied from ~5.5 to 8.8 calculated at the pump. In that 45,000 miles, I have averaged 7.3MPG.