Vapor Separator Fuel Delivery Test - Mercury 150 EFI Service Manual

2. Turn ignition key switch to "ON" position.
3. Operate electric fuel pump (ignition key on).
NOTE: Fuel pump will only operate for approximately 2-4 seconds. By turning the key
switch to "OFF" and then back to "ON" the pump will operate for 2-4 seconds more.
4. Take reading on fuel pressure gauge.
Results: If pressure reading is 41 to 45 psi (283 to 310 kPa), the electric fuel pump is providing fuel with
enough pressure to be used by the injectors. Pump malfunction is not the cause of EFI trouble.
If fuel pressure is well below 41 psi (283 kPa), fuel delivery to electric fuel pump, fuel pump
failure or other related problem exists. Inspect final filter for debris.
If fuel pressure is above 45 psi (310 kPa) go to fuel pressure regulator test.

Vapor Separator Fuel Delivery Test

Purpose: Verifying there is adequate fuel flow to the electric fuel pump (through full RPM range) will deter-
mine components in low pressure fuel system are functioning correctly.
1. Remove vapor separator drain plug and place a clean container under drain.
2. Prime fuel line primer bulb.
Results: Fuel should flow when plug is removed and continue to flow as primer bulb is pumped. If fuel flow is
not present, inspect pulse fuel pump, water separator filter or VST float and needle valve.
If fuel flow is present, go to High Pressure Flow Chart.
90-883728 JULY 2001
ON
OFF START
FUEL INJECTION
58891
Page 3B-21