Efi System Test Procedures; Fuel Gauge Connection/Pressure Test - Mercury 150 EFI Service Manual

FUEL INJECTION

EFI System Test Procedures

NOTE: A clogged final filter located in fitting above fuel pump will cause low fuel pressure
readings at the fuel pressure port. Remove fuel fitting and inspect final filter. Clean and/or
replace final filter as necessary.
a -

Fuel Gauge Connection/Pressure Test

IMPORTANT: When checking fuel pressure while engine is running, fuel pressure
may fluctuate. Fuel pressure fluctuation [i.e. 41 to 45 psi (283 to 310 kPa)] is com-
mon, as the regulated pressure is a differential between fuel rail and manifold vacu-
um.
Purpose: Checking fuel manifold pressure ensures that fuel under usable pressure is available to the fuel
injectors. This test isolates the probable cause as either a fuel delivery or EFI electrical system failure.
IMPORTANT: Fuel pressure should be monitored through full RPM range to deter-
mine fuel supply problems at high engine speeds.
1. Connect fuel pressure gauge to VST pressure port.
c
a -
b -
Page 3B-20
a
Final Filter
a
b
Pressure Port
Fuel Pressure Gauge
(91-881834A1)
58874
c - Direct fuel into suitable
container
90-883728 JULY 2001