The fuel pick up has an integrated fuel sending unit inside the plastic tube. The sending unit comprises a long narrow circuit board with 9-12 reed switches and several resistors. The reed switches are separated roughly 1 ½” apart on the circuit board. Between each reed switch are resistors. The resistors and reed switches are wired in a manner that as each reed switch closes from bottom (empty) to top (full), the total resistance across the circuit board increases. As a rule of thumb, the resistance range from empty (bottom) to full (top) is 90 to 0 Ohms regardless of model and year of SeaDoo. The reed switches are activated by a magnet that is attached to a float that rides up and down with the fuel level. The float is held in place by internal rails inside the unit but, it is allowed to float up and down with the fuel level.
Overall, it’s a pretty simple design. However, the fuel sending unit circuit board also has a one-time fuse. Once the fuse blows on the circuit board it renders the sending unit non-functional as the fuse can’t be replaced. This is the weak link in the system.
The following procedures test the fuel sending unit for 2-stroke caburetated SeaDoos. This test will not work on fuel injected or 4-TEC SeaDoos. With this test you do not need to remove the fuel baffle from tank. It’s a quick easy test that diagnoses most common problems with the fuel sending unit system. All you need for the test is an Ohm meter.
1. Locate the fuel sending unit and sending wires. The wire colors are pink and pink/black, and the wires are potted into the side of the fuel-sending unit. Follow these wires until you come to the inline 2-wire connector, then disconnect the connector.
2. Perform a resistance test on the fuel sending unit by connecting the Ohm meter to the pink and pink/black wire terminals running to the fuel sending unit.
3. Record the resistance and the approximate level of fuel in the tank.
4. Compare your readings to those below for a good sending unit:
1.1. 0-5 Ohms = Full Tank
1.2. 45 +/- Ohms = Half Full Tank
1.3. 85-95 Ohms = Empty Tank
If your Ohm meter reads an open circuit (infinite resistance), then the internal fuse is blown and the sending unit will need to be replaced.
If your resistance reading was 95-85 Ohms and the tank obviously has gas, the magnet has probably come loose from the float or the float has lost its buoyancy. If this is the problem, the fuel gauge would always show an empty tank of gas. This will require a new float be installed into the sending unit.
If your fuel gauge always shows the same reading (ie is stuck), then the float could be wedged inside the plastic tube. This is very rare, although I have seen the upper metal hose clamp be so tight that they pinch the fuel sending unit and wedge the float in place.
These are not the only potential failures, but they are the most common and probably 90% of the reasons the fuel sending units fail.
