Ignition
Page 2A-12 90-8M0050731 MAY 2011
2. Engine Cranks, Starts, and Stalls
Cause Action
2.0 Low air pressure in rail
Refer to 1.2.
2.1 Low fuel pressure in rail
Refer to 1.3 and 1.4.
2.2 Abnormally high friction in engine Check for scuffed piston or other sources of high friction.
2.3 Air in fuel system/lines
Refer to 1.3.
Crank and start engine several times to purge.
2.4 TPS malfunction
Check motion of throttle arm.
Stop nuts should contact block at idle and WOT.
Check TPS setup.
2.5 Remote control to engine harness connection is
poor
Clean and inspect male and female connectors.
3. Engine Idle is Rough
Cause Action
3.1 Low air pressure in rail (less than 79 ± 2 psi while
running)
Refer to 1.2.
3.2 Fouled spark plug
Replace spark plug:
‑ If carbon bridges electrode gap or if it is completely black.
‑ If it is not firing and is wet with fuel.
NOTE: If spark plug is gray or completely black with aluminum specs, this
indicates a scuffed piston.
‑ Wrong spark plug.
3.3 Failed direct injector Refer to specifications for ohm test.
3.4 Failed fuel injector Refer to specifications for ohm test.
3.5 Bad coil/weak spark Refer to specifications for ohm test.
3.6 Flywheel misaligned during installation Remove flywheel and inspect.
4. Engine Idles Fast (RPM > 700) or Surges
Cause Action
4.1 Broken fuel pressure regulator or tracker
diaphragm
Measure fuel pressure.
Remove and inspect diaphragms (a special tool is required for assembly).
4.2 Fuel leak
Check for fuel entering induction manifold or air compressor inlet.
Fuel pump diaphragm leaking and/or vapor separator tank is flooding.
4.3 Tracker valve spring missing Inspect tracker valve for proper assembly.
4.4 Improper setup Check throttle cable and cam roller adjustment.
5. Engine Runs Rough Below 3000 RPM
Cause Action
5.1 Fouled spark plug
Refer to 3.2.
5.2 Low air pressure in rail
Refer to 1.2.
5.3 Throttle incorrectly adjusted
Check throttle cam setup on induction manifold.
Inspect linkage and roller.
If throttle plate stop screws have been tampered with, contact Mercury
Marine Service Department for correct adjustment procedures.
5.4 Bad coil/weak spark
Refer to 3.5.
5.5 TPS malfunction
Refer to 2.4.
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