Ignition Troubleshooting And Fault Chart - Mercury 150 EFI Service Manual

Ignition Troubleshooting and Fault Chart

To protect against meter and/or component damage, observe the following pre-
cautions:
DO NOT reverse battery cable connections. The battery negative cable is (–)
ground.
DO NOT "spark" battery terminals with battery cable connections to check po-
larity.
DO NOT disconnect battery cables while engine is running.
Before troubleshooting the ignition system, check the following:
1. Make sure that electrical harness and ignition switch are not the source of the prob-
lem.
2. Check that plug-in connectors are fully engaged and terminals are free of corrosion.
3. Make sure that wire connections are tight and free of corrosion.
4. Check all electrical components, that are grounded directly to engine, and all ground
wires to see that they are grounded to engine.
5. Check for disconnected wires and short and open circuits.
Symptom
1. Engine cranks but won't
start
90-883728 JULY 2001
Cause
1.0 Lanyard stop switch in
wrong position.
1.1 Weak battery or bad starter
motor, battery voltage drops
below 8 volts while cranking
(ECM cuts out below 8volts)
(Fuel pump requires 9volts)
1.2 No fuel
1.3 Flywheel misaligned during
installation
1.4 Blown fuse
1.5 Main Power Relay not
functioning
1.6 Spark Plugs
CAUTION
Action
Reset lanyard stop switch.
Replace/charge battery.
Inspect condition of starter motor.
Check condition of battery termi-
nals and cables.
Check that primer bulb is firm. Key-
on engine to verify that fuel pump
runs for 2 seconds and then turn off.
Measure fuel pressure
Remove flywheel and inspect.
Replace fuse. Inspect engine har-
ness and electrical components.
Listen for relay to "click" when the
key switch is turned on.
Remove spark plugs from each
cylinder.
Connect spark plug leads to Spark
Gap Tester 91-830230T.
Crank engine or use DDT output
load test for each ignition coil and
observe spark. If no spark is pres-
ent, replace appropriate ignition
coil. If spark is present, replace
spark plugs.
IGNITION
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