Fuel Management Gauge MPG issue

[rmklaw01]

I have the four gauge installation for twin 2001 F115. Suddenly, I can no longer get a reading of MPG in the fuel management. I get the fuel consumption reading and I get speed and all other functions in the other gauges. This tells me that the signal is getting to the gauges but the fuel management is not computing MPG.

Is this an indication of a bad gauge or is there something else I need to look at before purchasing another gauge? I checked the plugs and wiring behind the gauges. Thanks for the help.

[rodbolt17]

the MPG signal comes from either the GPS or the speedometer, check the cables that supply the FMM with a speed signal.
GPH is a better more precise way to calculate fuel burn anyway.
MPG is to variable on the water.

[rmklaw01]

Thanks. I am getting the correct speed on the speed gauge and have a good connection from the speed gauge to the FMM. That is why I am suspecting a bad FMM gauge. All readings from the engines including speed, rpm and fuel consumption are showing. The only one not showing is MPG, which I use for trimming purposes only.

Am I missing something in my troubleshooting? Thanks.

[rodbolt17]

nope, but GPH is vastly superior to MPG when trimming for effenciency.
if I still had GPH then I would not spend the money.

[rmklaw01]

I just hate to see something not working.

[rmklaw01]

Other than the FMM gauge going bad, is there anything else that can cause to lose the MPG reading? All other readings are good including speed and GPH and total fuel consumption.

Just want to double-check before I plunge into a gauge replacement.