Test Return Fuel Pressure - Yanmar BY Series Service Manual

FUEL SYSTEM
Results
• If pressure reading is not within specification,
inspect fuel filter / water separator, fuel fine filter
and fuel feed pump.
• Measure vacuum / restriction before the electric
pump. Connect a suitable fuel vacuum gauge
assembly (Figure 6-7, (1)) inline between the fuel
tank and fuel feed pump, to measure vacuum.
This value should not exceed 1000 mmAq
(40 in.Aq). If it exceeds the specification, correct
restriction from the fuel tank to the engine.
Figure 6-7
Figure 6-7
Note: If fuel feed pump pressure is significantly
less than 5.0 bar (73.0 psi) and inlet
restriction and return line pressure are
within specifications, replace the electric
fuel feed pump.

Test Return Fuel Pressure

Note: This test is dependent on the fuel supply.
Test the low-pressure fuel system prior to
performing this test. See Measure Fuel
Feed Pump Pressure on page 6-9.
1. Assemble a tee, hose and 0 to 100 kPa
(0 to 15 psi) pressure gauge.
2. Disconnect the hose from the fuel return line
(Figure 6-8, (1)).
6-10
Figure 6-8
(1)
3. Connect test gauge assembly between
4. Start engine and allow speed to stabilize at
5. Read and record pressure.
0006657
Results
If test pressure reading is not within specifications,
find and correct the return fuel restriction.
© 2009 Yanmar Marine International
Tests and Adjustments
(1)
Figure 6-8
disconnected ends. Install and tighten hose
clamps.
normal low idle.
Specification
Inspection Item RPM
Return Fuel
All speeds
Pressure
BY Service Manual
0006658
Pressure
200 mmAq
(7.9 in.Aq)