ENGINE DIAGNOSIS - PERFORMANCE
CONDITION POSSIBLE CAUSES CORRECTION
ENGINE WILL NOT
CRANK
1. Weak or discharged battery. 1. Charge or replace battery as necessary.
(Refer to 8 - ELECTRICAL/BATTERY
SYSTEM - DIAGNOSIS AND TESTING).
Check charging system. Refer to the
appropriate Diagnostic Information for
charging system diagnosis.
2. Corroded or loose battery con-
nections.
2. Clean/tighten battery/starter connections.
3. Faulty starter or related circuits. 3. Check starting system. (Refer to 8 -
ELECTRICAL/STARTING - DIAGNOSIS
AND TESTING).
4. Seized accessory drive compo-
nent.
4. Remove accessory drive belt and
attempt to start engine. If engine cranks,
repair/replace seized component.
5. Engine internal mechanical failure
or hydrostatic lock.
5. (Refer to 9 - ENGINE - STANDARD
PROCEDURE - HYDROSTATIC LOCKED
ENGINE).
ENGINE CRANKS BUT
WILL NOT START
1. No spark. 1. Check for spark. Refer to the appropri-
ate Diagnostic Information for ignition sys-
tem diagnosis.
2. No fuel. 2. Perform fuel pressure test. Refer to the
appropriate Diagnostic Information for fuel
system diagnosis.
3. Low or no engine compression. 3. Perform cylinder compression test.
(Refer to 9 - ENGINE - DIAGNOSIS AND
TESTING - CYLINDER COMPRESSION
PRESSURE TEST).
ENGINE LOSS OF
POWER
1. Worn or incorrect gapped spark
plugs.
1. Replace spark plugs or set gap.
2. Dirt or water in fuel system. 2. Clean system and replace fuel filter.
3. Faulty fuel pump. 3. Replace fuel pump.
4. Incorrect valve timing. 4. Correct valve timing.
5. Blown cylinder head gasket(s). 5. Replace cylinder head gasket(s).
6. Low compression. 6. Test cylinder compression. (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING -
CYLINDER COMPRESSION PRESSURE
TEST)
7. Burned, warped, or pitted valves. 7. Install new or reface valves as neces-
sary.
8. Plugged or restricted exhaust. 8. Replace parts as necessary.
9. Faulty ignition cables. 9. Replace ignition cables as necessary.
10. Faulty coil(s). 10. Test and replace as necessary.
9 - 4 ENGINE ZB
ENGINE - 8.3L (Continued)
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