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TEST NTC-12ACHECKING THE ENGINE MECHANICAL SYSTEMS
Perform TEST NTC-1A Before Proceeding
At this point in the diagnostic test procedure, you have determined that all of theengine electrical
systemsare operating as designed; therefore, theyare not the cause of the driveability problem.
The following additional items should be checked as possible mechanical causes of the problem.
1. ENGINE VALVE TIMING- must be within specifications
2. ENGINE COMPRESSION- must be within specifications
3. CAMSHAFT LOBES- check for abnormal wear
4. ENGINE SPEED SENSOR PICK-UP- check flywheel slots for debris/deterioration
5. ENGINE EXHAUST SYSTEM- must be free of any restrictions
6. ENGINE DRIVE SPROCKET- must be properly positioned
7. POWER BRAKE BOOSTER- no internal vacuum leaks
8. FUEL- must be free of contamination
9. FUEL INJECTOR- plugged or restricted injector
10. FUEL INJECTION PUMP- must be properly timed
NOTE:Always look for any Technical Service Bulletins that may relate to the problem.
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TEST NS-SELNO START SELECTION MENU
NOTE:The battery must be fully charged before performing any test in this manual.
NOTE:If the engine will not crank or cranks but will not run, be sure to check the Sentry Key
Immobilizer Module (SKIM) for proper communication and trouble codes.
NOTE:With the DRB, attempt to read ECM trouble codes. If the DRB is unable to communicate with
the ECM, perform test NS-2A. If there are any trouble codes present they must be repaired before
continuing with the No Start Symptom diagnostics.
Below you will find a recommended procedure to correct a No Start Problem by symptom. They
should be performed in the order that they are listed.
Repairing a No Crank Condition..............................................NS-1A
Repairing a No Response Condition...........................................NS-2A
Repairing a No Start Condition................................................NS-3A
Repairing a Start and Stall Condition...........................................NS-4A
Checking the Engine Mechanical Systems......................................NS-5A
NOTE:A failed engine coolant temperature (ECT) sensor can cause a cranks but will not run or an
extended cranking before starting condition. This occurs when the ECT sensor calibration fails
(sensor indicates engine temp is warmer than actual engine temp) and the ECM cannot command
proper fuel quantity to the injection pump.
NOTE:For all component locations seeGeneral Information Section 4.0 in this manual.
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TEST NS-3AREPAIRING - NO START
Perform TEST NS-SEL Before Proceeding
*Perform Verification TEST VER-1A. **Check connectors - Clean / repair as necessary.
USING AN OHMMETER,
MEASURE THE RESIS-
TANCE OF THE FUEL
QUANTITY ACTUATOR
CAVITIES8&9.
FIG. 1
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TEST NS-3ACONTINUED - REPAIRING - NO START
*Perform Verification TEST VER-1A. **Check connectors - Clean / repair as necessary.
TEST NS-3A INSPECT ALL FUEL
CONTINUED FROM LINES FOR ARE ANY PROBLEMS YES REPAIR AS
THE PREVIOUS RESTRICTIONS LEAKS EVIDENT? NECESSARY.*
PAGE. OR OTHER PROBLEMS.
NO
REFER TO THE CHECK FUEL INJECTION
SERVICE MANUAL AND IS THE FUEL YES PUMP TIMING. CHECK
PERFORM THE FUEL PRESSURE OK? FUEL SUPPLY FOR
SYSTEM PRESSURE CONTAMINATION SUCH
TEST. AS WATER.*
NO
CHECK THE FUEL
PUMP DRIVE. IF OK,
REPLACE THE FUEL
INJECTION PUMP
ASSEMBLY.*
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TEST NS-4AREPAIRING A START AND STALL CONDITION
Perform TEST NS-SEL Before Proceeding
At this point in the diagnostic test procedure it is assumed that all of the engine electrical systems
are operating as designed and are not the cause of a start and stall, or a no start problem. The
following additional items should be checked as possible mechanical problems. Any one of these
items can produce a start and stall, or no start condition; none can be overlooked as a possible
cause.
1. ENGINE VALVE TIMINGÐ must be within specifications
2. ENGINE COMPRESSIONÐ must be within specifications
3. ENGINE EXHAUST SYSTEMÐ must be free of any restrictions
4. FUELÐ must be free of contamination
5. FUEL FILTERÐ must be free of any restrictions
6. INTAKE AIR DUCTÐ passages must be free of any debris
Always look for any Technical Service Bulletins that may relate to this problem.
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11.0 REQUIRED TOOLS AND EQUIPMENT
ammeter
DRB (diagnostic read-out box) scan tool
jumper wires and probes
ohmmeter
vacuum gauge
voltmeter
12.0 GLOSSARY OF TERMS
backfire,
popbackfuel ignites in either the intake or the exhaust system
BCMbody control module
cuts out,
missesa steady pulsation or the inability of the engine to maintain a consistent
rpm
DLCdata link connector (previously called ``engine diagnostic connector'')
detonation,
pre-ignitiona mild to severe ping, especially under loaded engine conditions
ECMengine control module
ECTengine coolant temperature sensor
EGRexhaust gas recirculation valve and system
generatorpreviously called ``alternator''
hard startThe engine takes longer than usual to start, even though it is able to
crank normally.
hesitation,
sag, stumbleThere is a momentary lack of response when the throttle is opened.
This can occur at all vehicle speeds. If it is severe enough, the engine
may stall.
IATintake air temperature sensor
lack of power,
sluggishThe engine has less than expected power, with little or no increase in
vehicle speed when the throttle is opened.
MILmalfunction indicator lamp
PDCpower distribution center
poor fuel
economyThere is significantly less fuel mileage than other vehicles of the same
design and configuration.
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