Dodge ZB 2005 Service Manual page 1215

DRIVEABILITY - GAS
P0300-MULTIPLE CYLINDER MIS-FIRE —
TEST
8 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 Fuel Injector actuation, start the engine to clean the
cylinder of fuel. Failure to do so could cause engine damage.
Remove special tool #C4390.
Start the engine and allow the fuel pressure to reach maximum pressure.
Ignition on, engine not running.
Using the DRBIII , 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?
Yes → Go To 9
→ Go To 10
No
NOTE: Turn the ignition off, remove the Fuel Pressure gauge, and connect
the fuel lines before continuing.
9 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
CAM LOBES - must not be worn excessively
CYLINDER LEAKAGE TEST - must be within specifications
VALVE SPRINGS - cannot be weak or broken
Are there any engine mechanical problems?
Yes → Repair as necessary.
→ Go To 17
No
10 Turn the ignition off.
Disconnect the Fuel Injector harness connector.
Ignition on, engine not running.
NOTE: When a Misfire is detected for a particular cylinder, the PCM will
shut down that cylinders Injector Control circuit.
With the DRBIII , erase DTCs.
Using a 12-volt test light connected to 12-volts, probe the Injector Control circuit.
With the DRBIII , actuate the Fuel Injector.
Does the test light blink/flicker?
Yes → Replace the Fuel Injector.
→ Go To 11
No
ACTION
Perform POWERTRAIN VERIFICATION TEST VER - 5.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
Continued
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APPLICABILITY
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