Seadoo GS Fuel Gauge Circuit Repair

[odonnse]

Hey everyone — new to the forums and already neck-deep in Sea-Doo surgery.


I’ve got a 1997 GS with a completely unmotivated fuel gauge. It was DOA when I bought the ski, and after a summer of guessing how much gas I had left (spoiler: not much), I decided to dig in.


Pulled the gauge this fall and did a little “bench test” science experiment. Applied 12 V to the pink wire and ground to black — which, according to the internet, should’ve made the needle leap heroically to Full. Instead… nothing. Not even a twitch.


So now I’ve fallen all the way down the rabbit hole: removed the acrylic face, extracted the PCB, and started poking around with the multimeter like it owes me money. I’m an electrical engineer by trade, so I’m confident I can track down the bad component and Frankenstein this thing back to life — but before I go too deep into reverse-engineering mode, has anyone already mapped out or repaired one of these?


Would love to compare notes, or even just get confirmation that this gauge isn’t powered by Sea-Doo black magic. Also, if anyone’s got a spare fuel needle lying around, I’d gladly buy one — mine met an untimely death during an overzealous disassembly session.


Thanks in advance, and happy wrenching to all the fellow tinkerers out there!

 

[etemplet]

If you are speaking of the large 3-1/4" gauges those are difficult to find and when you do they are expensive. Prices are very unfriendly. I'd check the fuel baffle first to make sure it is sending a good signal to the fuel gauge.

 

[odonnse]

If you are speaking of the large 3-1/4" gauges those are difficult to find and when you do they are expensive. Prices are very unfriendly. I'd check the fuel baffle first to make sure it is sending a good signal to the fuel gauge.

Yes, that’s the exact gauge I’m dealing with. Do you happen to know if applying 12 V between the pink and black wires should actually make the needle pin to full? From what I’ve read, that’s supposed to be the quick “is-it-alive” test — but mine stayed flatter than my motivation to stop tinkering.
I completely agree that verifying the sender is step one in most cases, but the ski is currently hibernating in storage about four hours away. I’ve just got the gauge with me for some winter bench diagnostics. Based on my pink-to-black 12 V test, I’m leaning toward the gauge itself being the culprit — unless there’s some secret Sea-Doo voodoo I’m missing in the wiring or signal path.
Appreciate the tip though — and yeah, I’ve seen the prices on replacement gauges… definitely “unfriendly.” Makes me even more motivated to revive this one!

 

[mikidymac]

I don't think that circuit is supposed to get 12V, it only uses the resistance of the baffle. But I am no electrical expert either, so take that for what it is worth.

 

[odonnse]

I don't think that circuit is supposed to get 12V, it only uses the resistance of the baffle. But I am no electrical expert either, so take that for what it is worth.

You might be right about that — after digging into it a bit more, I’m starting to think my “12 V across pink and black” test may not have been the correct approach after all. I’ve got most of the internal circuitry mapped out and partially reverse-engineered at this point, and so far it looks like I haven’t fried anything (which is always a plus).

I probably have a few more hours to go before I’ve got the full schematic nailed down, but now I’m starting to suspect the gauge might actually be fine — and that my initial “bench test” assumptions were what needed repairing!

 

[etemplet]

Old wires change color so that is difficult sometimes. Generally 2 pick wires from the fuel baffle send the resistance measurement to the fuel gauge. Usually the purple and black wires see power. Black= common, purple = 12 volts.

 

[lagojaguarasp]

Is it possible to remove the fuel sending unit on those GS/GSX hulls without removing the fuel tank out of the hull?

 

[etemplet]

Is it possible to remove the fuel sending unit on those GS/GSX hulls without removing the fuel tank out of the hull?

I'm pretty sure you can get remove the sending unit. You might have to get ugly with it.

 

[odonnse]

Old wires change color so that is difficult sometimes. Generally 2 pick wires from the fuel baffle send the resistance measurement to the fuel gauge. Usually the purple and black wires see power. Black= common, purple = 12 volts.

That was how I understood it, other than the pink wire also being powered. The issue is the fuel signal goes through the MPEM. So as far as the schematic tells me, its fuel sender -> magic black box -> fuel gauge. If someone had a schematic for the gs MPEM, that would help.

 

[etemplet]

I've worked on a number of Seadoos where the pink wires go directly to the fuel gauge. I guess it depends on the year.

 

[odonnse]

I've worked on a number of Seadoos where the pink wires go directly to the fuel gauge. I guess it depends on the year.

This is a 97 gs. Based on the wiring diagram, all the gauge wires go into the MPEM. My 96 SPI goes straight from the gauge to the sender. I wish the gs was like that.

 

[etemplet]

This is a 97 gs. Based on the wiring diagram, all the gauge wires go into the MPEM. My 96 SPI goes straight from the gauge to the sender. I wish the gs was like that.

Maybe give it a try. I kinda gave up on the fuel systems as it's easy enough to pop the hood and have a look. . That large gauge is so expensive and difficult to find. I wish some gauge manufacturers would get onboard and make something compatible. I like it when everything works.

 

[odonnse]

Maybe give it a try. I kinda gave up on the fuel systems as it's easy enough to pop the hood and have a look. . That large gauge is so expensive and difficult to find. I wish some gauge manufacturers would get onboard and make something compatible. I like it when everything works.

Yea, I like it all to work as well, maybe to my detriment. Well I hope to at least figure out the design and maybe help save a gauge from the scrap heap.

 

[artr]

If you look at the schematic for your ski I think the Purple line is 12V and the Black is ground. I think that because those lines go to another connector that has nothing else on it but would daisy chain the power to other gauges if your ski had them. I think, but I am not sure, that the the Pink line is the fuel baffle resistance and the Blue line is the oil sensor resistance, both measured to ground (look at the Instrument section under Electrical in the manual). They are just fed thru the MPEM. With no resistance, both measure infinite which would mean an empty fuel tank and low oil in the oil tank (so the light should be on). If the oil light is on then putting a very low resistance (2 ohms) or even grounding the Blue line should turn the oil light off. If that works you can try grounding the Pink line and the fuel gauge should read full.
Since you have the circuit board open and have electrical background, I would try to verify that the Purple and Black lines provide power and that resistance input to the Blue or Pink lines is appropriate before trying any of this.

 

[odonnse]

@artr

Appreciate the info! And I have been starting to make that conclusion as well. I think there is an issue on the 12V line because I get no power draw when it is connected and the oil light never comes on. The gauge is doing some comparison and level shifting of the Pink wire. I did attempt to short the pink to ground and 12v with no change in function. I hope to get back to the design review/mapping this week.

 

[artr]

Do you know if the oil light ever worked when the gauge was on the ski? It probably should have lit up for a short time when the key was placed on the post without starting or if the start button was pressed without a key.

 

[odonnse]

I don't recall it ever working.

 

[artr]

If you supplied 12V to purple and ground to the black and get no oil light and then grounded (and even tried 12V) on the pink line with no full tank reading it is probably a problem with the gauge. Hopefully you can track it down and correct it.
You could also verify on the ski if the pink wire from the MPEM is giving you a resistance reading or a voltage reading (both referenced to ground) that are commensurate with the level of fuel in the tank. That will tell you if the MPEM is just passing the resistance value from the fuel baffle or converting it to a voltage. The actual fuel baffle leads (pink and pink/black stripe) will give you a resistance reading between 0 and 90 ohms if it is working correctly.