'97 SLT700 Fuel Line Connections

[GoodWComputers]

I've been trying to figure out an answer to my question via searching the forums but have gotten only so far... on my '97 Polaris SLT700 project, I pulled out all the old fuel lines and forgot to take a picture or make a drawing of the connections. I read that the four nipples on top of the tank are labeled to show which fuel line connection goes where; is this true? I haven't checked mine yet because the top of the tank is pretty dirty. I'm about to go buy new fuel lines now.

[K447]

The nipple markings are on there, but they are quite small. Around the perimeter, embossed into the plastic.

Are you also replacing the fuel selector valve? If you have a fuel/water separator, be sure to clean it internally and check or replace the o-ring seal.

If you are ordering parts, new vent check valves will ensure the fuel tank internal air pressure is properly controlled. There are two for the fuel tank and another vacuum relief check valve for the oil tank.

[K447]

I just went outside and photographed this fuel sender.


You can clearly see the markings around the inner perimeter of the mounting flange.


Note that the two non-fuel supply nipples are opposite each other. VENT on one side, RETurn on the other side.



This sender is from a model that uses the MFD to provide the Low Fuel warning. This means the fuel selector valve only has ON and OFF, no Reserve position.

Perhaps confusingly, this also means the fuel sender does not have a MAIN nipple. Instead, the main fuel feed for the watercraft comes from the RES nipple.


If your watercraft actually has four nipples on the fuel sender, then the Reserve nipple feeds the Reserve position on the fuel selector valve, and the MAIN nipple feeds the ON position on the fuel selector valve.

If you connect these reversed, the ON position of the selector valve will draw from the RES feed inside the fuel tank. This will work just fine, up until the moment when fuel tank becomes empty. Then when you switch the valve to the Reserve position, you will in fact have already used up all the fuel in the tank, and the engine will not be able to run.

It is less critical whether you get the VENT and RET (Return) nipples swapped. Both just connect into the very top area of the fuel tank. One allows fuel to flow back into the tank when it returns from the carburetors, the other allows air to flow in and out of the tank as needed to maintain an approximate equilibrium with the outside air pressure.

[K447]

For completeness, here is a typical four hose fuel sender, for Polaris watercraft with an ON-OFF-Reserve fuel selector valve. This one is from a Hurricane 2410044.

Note that the MAIN connection is in the same place as the 'missing' nipple on the previous example.

The MAIN hose goes to the ON position on the fuel selector valve. The RES hose goes to the Reserve setting on the fuel selector valve.

This fuel sender was extracted from a Hurricane fuel tank;





Also note that the difference between the VENT and RETURN fittings is inside the fuel tank. The RET nipple just dumps fuel into the top of the fuel tank space.



The VENT nipple is connected to the interior of the aluminum extrusion, where it is somewhat protected from fuel sloshing around in the tank. The round hole in the back side of the aluminum tube is where the air in the fuel tank actually 'vents'.



Since this side hole is not at the absolute top of the fuel sender height, filling and burping the fuel tank to the absolute brim means the vent hole would be submerged in fuel. Expansion of the fuel with the sun's heat could conceivably force liquid gasoline out through the pressure release check valve and rubber hull grommet. Hopefully this does not actually happen very often.

Note: Since the fuel pump applies suction to the fuel supply nipple(s) on the fuel tank sender, it is important that the bottom end(s) of the supply nipple(s) be completely inserted and sealed into the top of the mating aluminum extrusion. If you find a gap between the top of the metal extrusion and the bottom of the plastic cap, there could be an air leak where the nipple is inserted down into the metal feed tube. Air leaks are not good as they reduce fuel pressure and flow volume, potentially allowing the carburetor(s) and cylinders to run lean, with potential for engine damage.

And here is where the RES fuel inlet actually picks up the fuel from near the bottom of the fuel tank. It is a straight tube right up to the RES nipple, no filter or even a mesh screen. This is why you want to keep the fuel tank clean on the inside!



The other small hole on the bottom is for the fuel level float, that is where the fuel flows in to allow the fuel level inside the float chamber to match the fuel level in the rest of the tank.

The MAIN fuel inlet is a small hole on the side of the aluminum, similar to the vent hole except the MAIN inlet hole is much lower down on the unit.