Special Tools
Fuel Pressure Gauge Kit 91‑881833A03
Tests the fuel pump pressure; can be used to relieve fuel pressure.
Dual Fuel/Air Pressure Gauge Kit 91‑881834A 1
Tests fuel and air pressure; the dual gauges allow the viewing of both pressures
simultaneously.
General Troubleshooting
For general troubleshooting information, including connecting and using the CDS G3 diagnostic tool, refer to Section 1E ‑
General T
roubleshooting.
Testing Fuel System Inlet Vacuum
1. Separate the engine fuel line and the boat fuel line.
2. Install a T‑fitting on the boat fuel line.
3. Install a clear fuel line on the opposite side of the T‑fitting.
4. Connect the clear fuel line to the engine fuel line.
5. Install a fuel vacuum gauge (obtain locally) on the T‑fitting.
6. Clamp all fuel line connections securely to prevent vacuum leaks.
7. Start the engine.
8. Monitor the clear fuel line for air bubbles.
9. At maximum fuel flow (wide‑open throttle operation), the vacuum gauge reading should not exceed the listed specification.
a - Engine fuel line
b - Clear fuel line
c - T‑fitting
d - Boat fuel line
Fuel System Inlet Vacuum
Maximum 8.5 kPa (2.5 in. Hg)
Fuel Pressure Test
1. Install a fuel pressure gauge onto the fuel rail service port.
a
b
c
d
4439
Troubleshooting and Diagnostics
Page 3B-2 © 2018 Mercury Marine 90-8M0125265 eng NOVEMBER 2017
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