Volvo D6 435 Error - Water in Fuel / Sensor Failure

[dbsea]

I spent the nite on my boat in Andrew’s Bay due to contracting Omicron (yes, triple vaxxed). When I woke up this AM, it was obviously very foggy and cold. I decided to start the engine to heat the water heater and recharge the batteries from overnight usage and running the inverter for coffee. When I tried to crank the engine, it threw an error on the Volvo screen that there was a sensor failure, and the Garmin screen said “Water in Fuel” in the warnings list. The engine did not start on that try. My anxiety level spiked. I cranked the engine again after dismissing the warning and it started as normal, and I ran it for 20 minutes. I turned it off and turned off the ignition, and restarted. All warnings went away.

Is this all a symptom of the very cold foggy morning, or something I should be looking at, and if the latter, what am I looking for?

Thanks…

 

[BB marine]

The water sensor is part of the drain for the secondary fuel filter. The switch senses the resistance between two pins, that are in contact with the fuel. If no water is detected in the fuel, the resistance is very high. If water is detected in the fuel, the resistance falls. At a threshold resistance (water has been detected), the switch output signal will cause the ECU to send out a code. The sensors are sensitive and will sometimes send false codes or intermittent. I suppose a extremely damp cold day may contribute to a false code but I would not over look it. Probably a false code because it did not repeat but I would still check the primary filter (Racor). This filter normally does not have a sensor but will be the first filter in line to remove water. It is easier to check than the secondary filter in most installations. If you find water in the Primary filter then the next step would be to check the secondary filter. This is the filter that has the sensor. If no water is found in the primary filter I would suspect that the code was a false code. There has been several threads on Tugnuts about false water in fuel codes.

 

[dbsea]

Thanks Brian! I was able to speak with the prior owner and he told me this error was actually related to a low start battery, and ironically nothing to do with the sensor or there being water in the fuel. This is odd, as the batteries are new AGM 31’s last year. Perhaps the cold, perhaps a fluke, i don’t know. I do need to go around and tighten all connections soon. That time of year again…