Author Topic: Fuel Gauge Reacts to Top Off  (Read 3946 times)

D. Wendal Attig

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Fuel Gauge Reacts to Top Off
« on: October 11, 2019, 04:55:12 PM »
I've never had any issues with the fuel gauge, but on a recent trip, we decided to top off the tank before departing since we would be traveling through an area where refueling was uncertain. 

After I filled it all the way up (first time in 3-1/2 years we have owned the coach) the fuel gauge initially read full (read fool!) then pegged a short time later to below empty.

Anyone else experienced this first hand, or seen this happen before?  If so, is there anything I can check or is there a remedy?

I appreciate your help, thoughts and advice.

Mike Shumack

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Re: Fuel Gauge Reacts to Top Off
« Reply #1 on: October 11, 2019, 07:28:45 PM »
From what I've read, most of these coaches (2000 era) use the Centroid brand fuel sending unit. http://www.centroidproducts.com/

Some have reported that algae in the tank can cause problems with the Sender. If algae builds up in the tank, and you don't typically keep the tank full, you could have a heavy build up at the top of the tank (as no fuel was there to wash down that area). That algae gets on Sender unit and builds up a coating.

You might try to add some biocide to the tank, fill the tank up fully, drive around and see if that helps clean things up.

Have you noticed any algae/buildup in the fuel filters?

Joel Ashley

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Re: Fuel Gauge Reacts to Top Off
« Reply #2 on: October 11, 2019, 11:36:54 PM »
Mike is probably on target, Wendal.  You should be in the habit of topping your coach up, especially before any long-term non-use.  Any airspace above the fuel can absorb moisture that algae thrives on.  Humid regions like the southeast and moist areas like the Northwest, or anywhere in between, are susceptible.  I try to fill the coach when the needle hovers around 1/2, and at the nearest station when almost home.

A biocide may help kill any existing algae, but depending on the degree of growth, it may take awhile to run its debris out, and could require a tank cleaning.  Power Service (and others) make other products aside from their Bio-Kleen, and those may help with cleaning.  But as Mike noted, your truth may be found in any glass bowl on your primary fuel filter.

https://powerservice.com/psp_product/bio-kleen-diesel-fuel-biocide/

Joel
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Fred Brooks

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Re: Fuel Gauge Reacts to Top Off
« Reply #3 on: October 12, 2019, 02:24:12 PM »
     Wendal,   Another consideration is to not introduce any more moisture to the fuel tank to help promote algae. If you live in an area where there is high humidity and there are large temperature swings from day to night, any exposed metal will accumulate condensation on the surface of the metal and then drip down into the tank. The only way to help, as we all have to deal with this, is to fill your fuel tank before putting your coach in storage and add fuel conditioner. Any residual moisture should be picked up by the fuel separator in the primary fuel filter.
  If you filled your fuel tank to a new height the fuel sender never experienced before, Mike is probably correct as the windings on the 90ohm sending unit could be mucked up. Drive the coach for a while and see if she behaves after a bit.
  I should have said add the conditioner first and then fill the fuel tank, sorry.  Fred
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Joel Ashley

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Re: Fuel Gauge Reacts to Top Off
« Reply #4 on: October 13, 2019, 03:24:45 AM »
Thanks Fred.  You serve to alert me that I wasn’t thorough enough when I said that “Any airspace above the fuel can absorb moisture that algae thrives on“. 

The less space above the fuel, the less moist air can exist in the tank, and the less cold sidewall space there is exposed for moisture to condense out onto while the coach is parked.

Joel
Joel and Lee Rae Ashley
Clackamas, Oregon
36.9 ft. 2006 Monterey Ventura IV, aka"Monty Rae"
C9 400HP Cat
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Gerald Farris

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Re: Fuel Gauge Reacts to Top Off
« Reply #5 on: October 14, 2019, 02:40:10 AM »
Wendal,
I will put in my 2 cents worth here. I do not think that diesel algae is the problem with your fuel gauge because the microbe growth that is called diesel algae (it is not really algae since it grows in total darkness and algae requires light) grows in the layer where the water in the bottom of the tank contacts the diesel fuel. This microbe growth will clog fuel filters, and the full tank storage method is the best way to prevent water in your tank therefore preventing the microbe growth.

The problem with your fuel sending unit is either poor continuity between the contact that rides on the resistor strip and the resistor strip, or a bad resistor strip. The vast majority of the time this problem requires replacing the fuel sending unit.

Gerald
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Diana Bentley

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Re: Fuel Gauge Reacts to Top Off
« Reply #6 on: November 27, 2019, 12:34:12 AM »
Don't know if this relates since the gauge read right before it went to zero, but Al De Costa, a fellow BAC member with no computer ask me to share his experience. With all of the disasters in California (fires, floods, heat) the rodent population in his area went wild. Some entered his coach and, among other things, chewed the wires on top of the fuel tank and something going to the atmospheric air hose and this affected his gauge readings. Needless to say, he had quite a bill to get everything working again.

Fred Brooks

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Re: Fuel Gauge Reacts to Top Off
« Reply #7 on: November 27, 2019, 01:10:31 PM »
    Diana, That is a reasonable possibility when you consider the fact that almost all automotive wiring uses soy bean oil in the manufacturing process of the wiring insulation. Fred
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2014 Honda CRV
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