Mariner Mercury 105/140 JET, Service Manual

Page: 239 / 797

3C-32 - FUEL SYSTEMS 90-824052R3 JUNE 2002
Results: If RPM increase occurs while injecting fuel
into disabled cylinder, clogged injector filter or
defective injector may be the problem.
Perform Induction Manifold Disassembly
(page 3C-38) for inspection.
NOTE: Injector fuel delivery can be tested with
manifold cover removed. See Injector Operation Test
(manifold cover removed) below.
RPM does not change when injecting fuel into bleed
fittings could indicate lack of compression, damaged
reeds, end cap seals, crankcase split line seal, or
crankshaft sealing rings.
Remaining tests on EFI components may require
some EFI disassembly. See EFI System
Disassembly following.
Injector Operation Test (Manifold
Cover Removed)
Purpose: This test determines if the injectors are
actually injecting fuel into the engine at a
normal rate.
WARNING
Do not start engine with induction manifold
cover removed. Disable ignition system prior to
doing this test.
Procedure A: STEP 1: Remove induction
manifold cover using procedures outlined
under “lnduction Manifold Removal.”
STEP 2: Re-attach induction manifold to engine
using 1/4-20 x 2-3/4
″
screws.
STEP 3: Connect a jumper wire between the
ECM metal case and a good engine
ground.
STEP 4: Disconnect all spark plug wires from
spark plugs and seal leads with electrical
tape to prevent sparking.
STEP 5: Put ignition key switch in “START”
position.
OFF
ON
START
STEP 6: Look at injector spray pattern using an
explosive proof flashlight.
Results A: If fuel spray is not present in all injectors
or spray pattern is extremely weak, check wir-
ing harness to injector connectors, or injector
filters for plugging.
If spray patterns are available in most of the injectors,
but not all, perform Procedure B.