Mercury 3.0 Liter Service Manual download pdf (Page 49)

90-898303 2-46

Injector Electrical Harness Test

Purpose: This test will determine if electrical or fuel delivery problem exists

during the fuel delivery process by checking for open circuits in injector

harness.

1) With outboard in water, start and allow to warm up. Raise engine speed to

2000-2500 RPM. Remove spark plug leads one at a time and note RPM

change. Determine nonworking (no RPM change) cylinder. Stop engine.

2) Disconnect injector harness (4 pin connector).

IMPORTANT: Use digital ohmmeter when testing injector harness.

3) Connect digital ohmmeter (dial set at 200 scale) leads. POSITIVE lead

from ohmmeter connects to POSITIVE prong “2” (RED wire) of harness

connector. Connect NEGATIVE lead from ohmmeter to the remaining

wires of harness connector as follows:

WHITE Lead = Injectors, Cylinders 1 and 2

DARK BLUE Lead = Injectors, Cylinders 3 and 4

YELLOW Lead = Injectors, Cylinders 5 and 6

1) YELLOW

2) RED

3) DARK BLUE

4) WHITE

Results: If readings are 1.1 ± .2 both injector circuits are complete. Perform

Injector Fuel Delivery Test.

If readings are 2.2 ± .2 one injector does not have a complete circuit. Perform

induction manifold disassembly and inspection following.

Notes

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Mercury 3.0 Liter Service Manual Page 49