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Old 06-28-2021, 09:34 AM   #1
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Cummins 8.9L Fuel Gallon Totalizer

I have a 2013 Tour with Freightliner Maxum / Cummins 8.9L

The dash panel has the standard Freightliner LCD info screen that gives fuel consumption, engine temps etc.

However the fuel totalizer always reads about 20% optimistic. For example when the Trip Meter says I have burned 100 gallons I actually need 120 gallons to fill. I expect the MPG and other displays are also out as they rely on the same data. Is reading ~10MPG when I am probably only ~8MPG.

Is there a way to calibrate the fuel meter on Cummins engines?
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Old 06-28-2021, 01:24 PM   #2
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It's all computed via the ecm. However it doesn't compute generator usage.
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Old 06-28-2021, 05:03 PM   #3
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Originally Posted by Wild Card View Post
It's all computed via the ecm. However it doesn't compute generator usage.
Yes I wonder why the ECM ‘fuel consumed’ calculation is out by so much. I havent been using the generator.

It must be calibrated somehow.
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Old 06-28-2021, 05:44 PM   #4
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Ours is *very* close. If not running the genny, within a few gallons.

There are two things to check. One is that the mileage is accurate. if the wheel size has been set incorrectly, your mileage (and speed!) will read low. The other is that the fuel metering measurement is accurate.
1976 Southwind 28', '96 Winnie 34WK,
2006 Tiffin Allegro Bus 40QDP
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Old 06-30-2021, 06:48 PM   #5
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Mine always read about 7-9% too high. Too high mpg, too few gallons used. I think most people are quoting these calculated OEM ECM figures when you read them here.
" I Get 10 mpg with my 50k lbs coach going 75 mpg into a head wind pulling a 350 pick up" Ya right....
Only recorded gallons and miles are accurate if calculated correctly.
Full Timers.
2015 Fleetwood Discovery 40E on a Freightliner XCS chassis with a Cummins ISL9 pulling 1 and/or 2 motorcycles, '07 Honda Accord OR a 17' Runabout Boat.
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cummins, fuel

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