Ignition
90-8M0050731 MAY 2011 Page 2A-11
Troubleshooting Guide
1. Engine Cranks, but Will Not Start
Cause Action
1.0 Lanyard stop switch in wrong position Reset lanyard stop switch.
1.1 Weak battery or bad starter motor, battery voltage
drops below 8 volts while cranking (PCM cuts out
below 8 volts) (fuel pump requires 9 volts)
Replace/charge battery. Inspect condition of starter motor.
Check condition of battery terminals and cables.
1.2 Low air pressure in rail (less than 70 psi at
cranking)
Inspect air system for leaks.
Inspect air filter for plugging (air pressure measured on port rail).
Inspect air compressor reed valves, if necessary.
1.3 No fuel
Check that primer bulb is firm.
Key‑on engine to verify fuel pump runs for two seconds and then turns off.
Measure fuel pressure (valve on port rail).
Fuel pressure should be 96.5 kPa ± 6.9 kPa (14.0 ± 1.0 psi) greater than the
air pressure.
1.4 Low fuel pressure
Check fuel pressure from low pressure electric fuel pump
137.9 kPa–206.8 kPa (20–30 psi).
Check for fuel leaks.
If fuel pressure leaks down faster than air pressure, seals on fuel pump may
be leaking.
Check air system pressure, see 1.2.
1.5 Flywheel misaligned during installation Remove flywheel and inspect.
1.6 Blown fuse
Replace fuse.
Inspect engine harness and electrical components.
1.7 Main power relay not functioning Listen for relay to click when the key switch is turned on.
1.8 Spark plugs
1.
Remove fuel pump fuse.
Unplug all direct injector connectors.
Remove spark plugs, one at a time, from each cylinder.
Connect spark plug leads to spark gap tester.
Crank engine, or use CDS output load test, for each ignition coil and observe
spark.
If no spark is present, replace appropriate ignition coil.
If spark is present, replace spark plugs.
1.9 PCM not functioning
Injection system:
Listen for injector ticking when cranking or connect spare injector to each
respective harness.
Ticking should start after two cranking revolutions.
Ignition system:
‑ Check for proper operation by using an inductive timing light.
‑ Check battery voltage while the engine is cranking, there should be no less
than 8 VDC at the power stud.
‑ Check for blown fuse.
‑ Check battery voltage to fuse from main power relay (purple).
‑ Check for shorted stop wire (black/yellow).
A PCM with internal coil drivers can cause a loss of spark on all cylinders if
the internal coil drivers were damaged by a shorted ignition coil. Test all
ignition coils before replacing the PCM.
1.9A Crankshaft position sensor not functioning
Check crankshaft position sensor.
Defective PCM.
Check battery voltage while the engine is cranking, there should be no less
than 8 VDC at the power stud.
1. Spark jumping the gap from all cylinders at the same time in the spark gap tool may cause interference in the PCM. The interference may cause
the absence of spark on some cylinders and a false diagnosis of a no spark condition. Crank engine over with only one spark plug wire connected
to spark gap tool at a time or use CDS to fire one cylinder at a time.
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