Troubleshooting approach

[ScottyCee]

Howdy howdy.
I have a 2005 Yamaha 225 pair and fuel management system gauge is not operational. I have spent zero time troubleshooting this, but I would be super appreciative of anyone giving me a logical stepwise approach to dive in.

Thank you in advance.

Scott

 

[Fishtales]

I'd measure voltage to the unit first. How are the other gauges? They get dim over time (can be reworked), could it be working but not readable?

 

[SkunkBoat]

Troubleshooting step #1; What do you mean by "not operational"?

 

[Salmondogs]

Need a little more info on what isn't working...But I just "fixed" one on a friends Hewes Craft, the power wire was disconnected behind the dash haha. The illumination wire was still connected so the gauge would light up but the screen was blank, tucked my head under the dash and there was a bullet connector with red wires that was disconnected.

 

[ScottyCee]

Thanks guys. Thorough analysis is on the slate for this morning.

 

[ScottyCee]

Turned into a little bit bigger project than I had thought. There was a lot of weirdness like extensions that were added because somebody didn’t want to take out all the zip ties and redo properly when it was re-powered. So a mechanic friend and I basically started over. Looks great now.

The fuel management gauge is dead. Doesn’t light up with power, so replacement will be ordered.

 

[seasick]

Turned into a little bit bigger project than I had thought. There was a lot of weirdness like extensions that were added because somebody didn’t want to take out all the zip ties and redo properly when it was re-powered. So a mechanic friend and I basically started over. Looks great now.

The fuel management gauge is dead. Doesn’t light up with power, so replacement will be ordered.

Check the ground connection first.

 

[ScottyCee]

Thank you. Good tip. Yeah, the three other gauges work and power and ground are confirmed. Crossing my fingers that the senders are good. No reason to think they wouldn’t be, But I guess you don’t know until you know...

 

[seasick]

Thank you. Good tip. Yeah, the three other gauges work and power and ground are confirmed. Crossing my fingers that the senders are good. No reason to think they wouldn’t be, But I guess you don’t know until you know...

Regardless of senders, the gauge will power up and go though self test. If the display is totally blank, the gauge is either bad or is not getting power.

 

[ScottyCee]

Oh, it's dead all right...

 

[ScottyCee]

So, installation of a replacement gauge made all the difference. It’s wired in
per the schematic below and appears to work just fine. The only thing that seems odd is this gauge powers on with one key but not the other. is this how they are supposed to work?

yamaha fuel management wiring diagram - Google Search

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[Fishtales]

I'm guessing the power is switched by one of the keys as you say. Should be fine. Good to know you got it sorted out.

 

[ScottyCee]

thank you for the reply. Yes, it is. And that's how the wiring diagrams show it. Problem is there's a scenario when you're trolling with one motor running and if it doesn't happen to be the one the fuel management meter is powered from then you are without that functionality. I am simply wondering if that is by design or if there's a tricky way to work around it.

 

[SkunkBoat]

Thats the way my Yamahas were. Fuel management was powered by the Stbd key. If trolling on the other motor, you can turn on the key without starting..eventually the buzzer stops..I think...

maybe it was the port key...hmmmm...

 

[seasick]

I wonder if leaving the ignition on but not starting the motor may be an issue.
Some ECUs are water cooled. I don't know if that applies in this case, but should that be the case, the ECU could the ECU possibly overheat? In addition, the high pressure fuel pumps will be running and I am not so sure that is a good idea either.

 

[Salmondogs]

Thats the way my Yamahas were. Fuel management was powered by the Stbd key. If trolling on the other motor, you can turn on the key without starting..eventually the buzzer stops..I think...

I know all large computer controlled Mercury engines are shipped from the factory set as a starboard engine and the installer has to configure it as something else, so any engine accessory device that is controlled by ignition on power (gauges) is powered off starboard engine key up. I believe most other manufacturers do something like this too.

 

[seasick]

The Smartcraft speedo is wired to the starboard harness usually so you have to turn on that engine to see data on the speedo. Certain sensor data is taken from both motors and combined as needed for specific Smartcraft display data. Fuel burn is one of those.
On twins, one motor has to be programmed as port. As mentioned, starboard is the default. The programming has to be done using the Mercury DDT tool.

 

[Salmondogs]

The Smartcraft speedo is wired to the starboard harness usually so you have to turn on that engine to see data on the speedo. Certain sensor data is taken from both motors and combined as needed for specific Smartcraft display data. Fuel burn is one of those.
On twins, one motor has to be programmed as port. As mentioned, starboard is the default. The programming has to be done using the Mercury DDT tool.

All accessory gauges other than a SmartTach (accessory speedo, fuel gauge, and any other accessory smart craft gauge) are (or at least should be if you follow the rigging manual) piggybacked and powered off the stbd engine harness. Since fuel burn is available on the smart tach (I wish my Yamahas did that) there is no need for a separate gauge. Of course if you have a Vessel View then it has power anytime the engine CAN bus (older Vessel View models) or engine NEMA gateway has power which is whenever any engine is keyed up. On a side note I haven't seen a DDT in FOREVER lol. But since they aren't supporting the original CDS anymore I may have to go find one now!

 

[Salmondogs]

thank you for the reply. Yes, it is. And that's how the wiring diagrams show it. Problem is there's a scenario when you're trolling with one motor running and if it doesn't happen to be the one the fuel management meter is powered from then you are without that functionality. I am simply wondering if that is by design or if there's a tricky way to work around it.

Again I'm not supper familiar with how Yamaha does things but the in-laws 228 Seafarer has fuel burn integrated into the Garmin unit via NEMA. I believe it uses the Yamaha fuel flow management and it works even when trolling on the kicker with the main 200hpdi ignition off. I'll have to look at it next time I'm over at their house.

 

[seasick]

I think that most Yamis uses a fuel flow sensor to measure gas usage. Mercury on the other hand (at least my Optis) use a different and somewhat ingenious method. The engine ECU knows what the fuel delivery rate is for the injectors and it multiplies that by the total time that the injectors are open. That way, no fuel flow sensor is needed.