Mariner Mercury 105/140 JET, Service Manual

Page: 246 / 797

90-824052R3 JUNE 2002 FUEL SYSTEMS - 3C-39
Condition Possible Source Action
Engine Idles Rough (May Lean
Sneeze) – Acceleration Ok; Full
Throttle Ok. – Improper EFI Set Up.
– MAP Sensor Failure.
– Low Speed Winding Failure.
– Broken Reed.
Refer to Section 2A Electrical and
Ignition for proper EFI set up pro-
cedures.
Refer to Electronic Fuel Injection
Tester Manual 91-11001A2.
Refer to Section 2A Electrical and
Ignition Tests.
Perform Injector Fuel Delivery
Test (page 3C-31).
Engine Runs but Slowly Drops
RPM then Dies. – Restrictions in Fuel System
between Tank and Engine.
– Clogged Final Filter.
– Pulse Fuel Pump Failure.
– Electric Fuel Pump Delivery
Failure.
Install remote gas tank with fresh,
high quality fuel.
Perform Final Filter Check (page
3C-26).
Follow Low Pressure Fuel Route
Flow Chart (page 3C-19).
Follow High Pressure Fuel Route
Flow Chart (page 3C-20).
Engine Stops for No Apparent
Reason or Does Not Start. – Battery Undercharged.
– EFI Harness Connections.
– Ignition System Failure.
– Pulse Fuel Pump Failure.
– Electric Fuel Pump Failure.
– ECM Failure.
Check battery connections, under
charged battery or worn out bat-
tery.
Check EFI harness connector for
improper connection.
Refer to Section 2A Electrical and
Ignition Tests.
Follow Low Pressure Fuel Route
Flow Chart (page 3C-19).
Follow High Pressure Fuel Route
Flow Chart (page 3C-20).
Refer to Electronic Fuel Injection
Tester Manual 91-11001A2.
Engine Stops for No Apparent
Reason, but will Restart. – Battery Overcharged.
– Restriction in Fuel System
Check battery voltage with engine
running. Should be less than 15.5
volts. Refer to Service Bulletin
96-2.
Check fuel pressure on fuel rail at
the RPM that failure occurs.
*R.F.I. Radio Frequency Interference. High voltage can alter signals ECM receives from sensors causing im-
proper fuel delivery. Route all sensor wires away from high voltage leads (i.e. spark plug leads)