Fuel Gauge Accuracy

[griervictoria]

I have been noticing that my Volvo fuel gauge reading becomes quite different to that in the Garmin program readout.
Garmin said I had 68 gals left in the tank. Volvo engine gauge read 103 gals.
When I filled up with diesel, the tank took 109 gals, therefore the Garmin reading of 68 (+109) = 177gals compared to the engine gauge of 103 (+109) = 212 was closer to the mark.
Has anyone one had similar experiences and secondly is there a way to correct the Volvo gauge?

 

[baz]

A lot depends on the Garmin accuracy when you enter the gallons you've filled with.

You start off configuring the Garmin with you tank capacity. Then when tank is empty to begin with you enter the amount you fill. Each time you do this and enter the amount of fuel you put in that tank Garmin will keep a good tally. If you enter inaccurate numbers or simply forget to enter the number of gallons you put in the tank then Garmin will have an incorrect readout of remaining gallons.

If I were you I'd start afresh and goto the Gamin gauges and indicate how big your tank is. Then fill the tank and indicate to Garmin the amount you filled up with.

On my boat that has a 150 gallon tank I configure Garmin with my tank capacity being 145 gallons. I like to have that 5 gallons as a safety margin. When I fill up the tank with say 60 gallons I tell Garmin that. In this way my Garmin keeps an accurate tally of my remaining fuel gallons.

 

[griervictoria]

When I fill up the tank I have always adjusted the Garmin to reflect the fuel input, so it always starts out with a full tank 180 gals on both engine gauge and Garmin. By the time my tank is half empty, the large discrepancy has kept on occurring. Thanks for your comment though.

 

[ixlr8]

When I fill up the tank I have always adjusted the Garmin to reflect the fuel input, so it always starts out with a full tank 180 gals on both engine gauge and Garmin. By the time my tank is half empty, the large discrepancy has kept on occurring. Thanks for your comment though.

I gathered from your original post, the error is showing up in the Volvo display, not the Garmin display. Is this correct?

 

[baz]

If that’s the case then believe Garmin and not the engine display. Many people complain about this and use the Garmin as it appears to be more accurate.

On my boat I do not take the Yamaha engine display with any confidence at all. This is because it relies on the fuel level sensor which can stick at times plus the fuel sloshes to the rear of the tank making the engine display for remaining fuel higher than what it really is. The Garmin on the other hand is using an equation based on fuel burn as sent to it from the engine controller and will be far more accurate. Your boat may have the same issues as mine and others.

 

[knotflying]

When I fill up the tank I have always adjusted the Garmin to reflect the fuel input, so it always starts out with a full tank 180 gals on both engine gauge and Garmin. By the time my tank is half empty, the large discrepancy has kept on occurring. Thanks for your comment though.

In my opinion, on the Garmin, when I fill up my tank I hit the "fill tanks" button rather than the amount put in. The reason I do this is, there is a little additional fuel that works up the fill line and vent, hence probably a gallon or so more that the tank capacity. Over time this can add up and start to show inaccurate amounts remaining.

 

[Cutwater28GG]

the only fuel gauge I pay attention to is the Garmin. the other is useless.

that being said you have to be careful with the Garmin.

Generally I "reset" the Garmin to a known quantity every few fuel additions by carefully topping off the tank and then setting the Garmin to "fill up all tanks" to 100 Gal. I then track usage and to avoid a risk of spill add fuel close to used. so if the garmin says I have used 32 Gal.s I add 30 Gals and add 30 gals in the garmin. (I usually round down when adding to the number on the garmin to create a little positive buffer)

what I have noticed in reality is even with the round down I can quickly get out of sync by at least 10-15% even with only three 30ish gal fuel ups.

so you must fuel up to max at regular occurrences and "fill up all tanks" to reset the onboard fuel quantity to an accurate known level.

Also note whilst minimal, the diesel heater uses fuel without Garmins knowledge.

 

[griervictoria]

I just came back following 5days cruising the Gulf Islands, including the fuel stop. Following that in which I reset the Garmin to full and the engine gauge showed 180 gals, I cruised about 3 hours after this fill up and Garmin shows 169gals and the Volvo gauge reads 177, so I get that the Garmin is the one to monitor. In addition I never allow the gauge to go below 50 gals, so should not run her "dry". In this fall cruising we do use the Webasto for heat in the evenings so am aware that this is not recorded by Garmin, so I will continue to not run the fuel down to even close to the red zone.
Thanks again for your comments.

 

[knotflying]

The wabasto is pretty economical with fuel. If you are really concerned just keep track of the amount of time you use it and you can just add that to your consumption. I can't remember the exact numbers, but it is in the manual.

 

[Levitation]

For those boat owners who are not pilots, 'your fuel gauge is your watch'
Know how much is in when you fill/add fuel - this is your starting point each time.
Keep a log at the helm showing the running time - 15 minutes here, 2.2 hours there, etc.
Know your average fuel burn per running hour (estimate it to begin with, after a few tanks you will see what your actual use is)
When your watch says it is time for fuel it is time.