TEST ACTION APPLICABILITY
7 Warning: The fuel system is under a constant pressure (even with the engine
off). Before testing or servicing any fuel system hose, fitting or line, the fuel
system pressure must be released.
CAUTION:After each actuation of the Fuel Injector, start the engine to clear
the cylinder of fuel. Failure to do so could cause engine damage.
Install a Fuel Pressure Gauge to the fuel rail.
Start the engine and allow the fuel pressure to reach maximum pressure.
Turn the engine off, leaving the ignition on.
Using the DRBIIIt, actuate the Fuel Injector for the cylinder that indicated the
misfire.
Monitor the fuel pressure gauge.
Does the fuel pressure gauge indicate a drop in fuel pressure?
All
Yes → Go To 8
No → Go To 9
8 Check for any of the following conditions/mechanical problems.
ENGINE VACUUM - must be at least 13 inches in neutral
ENGINE VALVE TIMING - must be within specifications
ENGINE COMPRESSION - must be within specifications
ENGINE EXHAUST SYSTEM - must be free of any restrictions or leaks.
ENGINE PCV SYSTEM - must flow freely
TORQUE CONVERTER STALL SPEED - must be within specifications
POWER BRAKE BOOSTER - no internal vacuum leaks
FUEL - must be free of contamination
Are there any engine mechanical problems?
All
Yes → Repair as necessary.
Perform POWERTRAIN VERIFICATION TEST VER-5-NGC.
No → Go To 17
9 Turn the ignition off.
Disconnect the Fuel Injector harness connector.
Ignition on, engine not running.
With the DRBIIIt, actuate the ASD Relay.
Using a 12-volt test light connected to ground, probe theASD Relay Output circuit at
the Fuel Injector harness connector.
Does the test light illuminate brightly?
All
Yes → Go To 10
No → Repair the ASD Relay Output circuit.
Perform POWERTRAIN VERIFICATION TEST VER-5-NGC.
10 Turn the ignition off.
Disconnect the Fuel Injector harness connector.
Ignition on, engine not running.
Using a 12-volt test light connected to 12-volts, probe the Injector Control circuit.
With the DRBIIIt, actuate the Fuel Injector.
Does the test light blink/flicker?
All
Yes → Replace the Fuel Injector.
Perform POWERTRAIN VERIFICATION TEST VER-5-NGC.
No → Go To 11
116
DRIVEABILITY - NGC
P0300-MULTIPLE CYLINDER MISFIRE — Continued
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