Troubleshooting; Fuel Pressure Gauge Setup And Use - Mercury MerCruiser Service Manual

MPI ECT Fuel System

Troubleshooting

Fuel Pressure Gauge Setup and Use

Failure to release pressure from the fuel system will result in fuel spraying out, which can cause a fire or explosion. Allow the
engine to cool completely and release all fuel pressure before servicing any part of the fuel system. Always protect eyes and
skin from pressurized fuel and vapors.
Fuel is flammable and explosive. Ensure that the key switch is off and the lanyard is positioned so that the engine cannot
start. Do not smoke or allow sources of spark or open flame in the area while servicing. Keep the work area well ventilated
and avoid prolonged exposure to vapors. Always check for leaks before attempting to start the engine, and wipe up any
spilled fuel immediately.
Installation
IMPORTANT: Wipe up spilled fuel immediately.
1. Remove the Schrader valve cap.
IMPORTANT: Disconnecting the fuel pump does not ensure that the engine will not start. Be prepared for the possibility of
the engine starting.
2. Preferred method: Disconnect the fuel pump and crank the engine to bleed off fuel pressure.
3.
Optional method: Activate the Schrader valve located on the fuel rail to relieve pressure.
4. Using a proper adapter, attach the fuel pressure gauge to the Schrader valve.
Fuel Pressure Gauge Kit
Digital Pressure Meter
5. Turn the key switch on to purge all of the air from the fuel pressure gauge line.
NOTE: Turn the key switch on and off several times to purge the air from the line.
Test
1. Ensure that the fuel pump is connected.
2. Remove the reference line.
3. Turn the key switch on.
4. Observe the reading on the gauge. The reading should be within specification.
Fuel Pressure
With reference line removed
At idle, with reference line connected
5. Correct the problem if the reading is out of specification.
6. Reattach the reference line.
Without sufficient cooling water, the engine, the water pump, and other components will overheat and suffer damage. Provide
a sufficient supply of water to the water inlets during operation.
7. Provide cooling water to the engine.
8. Start the engine.
9. Check the fuel pressure; it should be
10. Remove the reference line.
11. Observe the reading on the gauge. The fuel pressure should return to full pressure (the same reading as with the engine
not running).
12. Reattach the reference line. The pressure should drop back to the initial pressure with the engine running.
13. Stop the engine.
14. Turn off the cooling water.
15. Correct the problem, if the system is out of specification.
Page 5A-30
CAUTION
!
WARNING
!
NOTICE
lower than the previous specification.
© 2016 Mercury Marine
91‑881833A03
91‑892651A01
Reading on Fuel Pressure Gauge
358 kPa ± 14 kPa (52 psi ± 2 psi)
296 kPa ± 14 kPa (43 psi ± 2 psi)
90-8M0099748 eng DECEMBER 2015