Fuel gauge malfunction

[SummaryGiraffe]

Was out on the lake this morning on my 1997 XP that I bought a couple months ago. Fuel gauge seemed to be working fine every time I’ve used it until about half way through today where it went from about half a tank right up to full and stayed at full. I know nothing about working on these machines but would like to learn. Any advice on where to start with this problem?

 

[artr]

Fuel gauge seemed to be working fine every time I’ve used it until about half way through today where it went from about half a tank right up to full and stayed at full.

Your picture seems to show the fuel gauge at empty. Is the ski shut off in that picture?

 

[SummaryGiraffe]

Your picture seems to show the fuel gauge at empty. Is the ski shut off in that picture?

Yes it was shut off, sorry I was just attaching a photo from the day to show the gauges for reference.

 

[artr]

There is a description of how to test the fuel gauge in the 97 shop manual which you can download at seadoomanuals.net. It is in the electrical section. It says that the resistance measurement increases as the fuel level drops. There is no schematic I've seen for the circuit board inside the fuel baffle. It would be easier to explain if your fuel gauge went to empty at and below half a tank. That would happen if the resistor at that point on the board failed open circuit or fell off the board. The open circuit would be an infinite resistance from that point and lower which the MPEM would read as an empty tank. Yours is the opposite and would need to test as a short circuit or very low resistance from the half way point and lower in order to read as a full tank. You could try just disconnecting the electrical plug with 2 wires that connects to the top of the fuel baffle when there is less that half a tank. The ski does not need to be on. Measure the resistance between the 2 wires and if it matches a value in the table in the manual for below half a tank then the problem is either in those 2 wires that connect to the MPEM or in the MPEM itself. If it measure a short circuit or very low resistance than something is wrong on the circuit board or internal to the baffle.