The 3.7 liter (226 CID) six-cylinder engine is an 90° single overhead camshaft engine. The cast iron cylinder block
is made up of two different components; the first component is the cylinder bore and upper block, the second com-
ponent is the bedplate that comprises the lower portion of the cylinder block and houses the lower half of the crank-
shaft main bearings. The cylinders are numbered from front to rear with the left bank being numbered 1,3, and 5
and the right bank being numbered 2,4, and 6. The firing order is 1–6–5–4–3–2. The engine serial number is
located at the right front side of the engine block.

DR/DH

ENGINE - 3.7L - SERVICE INFORMATION

9 - 2039

DIAGNOSIS AND TESTING

DIAGNOSIS AND TESTING - ENGINE DIAGNOSIS - INTRODUCTION

Engine diagnosis is helpful in determining the causes of malfunctions not detected and remedied by routine main-
tenance.

These malfunctions may be classified as either performance (e.g., engine idles rough and stalls) or mechanical
(e.g., a strange noise).

(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING) - PERFORMANCE and (Refer to 9 - ENGINE - DIAGNOSIS
AND TESTING)—MECHANICAL for possible causes and corrections of malfunctions. (Refer to 14 - FUEL SYSTEM/
FUEL DELIVERY - DIAGNOSIS AND TESTING) and (Refer to 14 - FUEL SYSTEM/FUEL INJECTION - DIAGNO-
SIS AND TESTING) for the fuel system diagnosis.

Additional tests and diagnostic procedures may be necessary for specific engine malfunctions that can not be iso-
lated with the Service Diagnosis charts. Information concerning additional tests and diagnosis is provided within the
following diagnosis:

•

Cylinder Compression Pressure Test (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

•

Cylinder Combustion Pressure Leakage Test (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

•

Engine Cylinder Head Gasket Failure Diagnosis (Refer to 9 - ENGINE/CYLINDER HEAD - DIAGNOSIS AND
TESTING).

•

Intake Manifold Leakage Diagnosis (Refer to 9 - ENGINE/MANIFOLDS/INTAKE MANIFOLD - DIAGNOSIS
AND TESTING).

DIAGNOSIS AND TESTING - ENGINE DIAGNOSIS - PERFORMANCE

CONDITION

POSSIBLE CAUSE

CORRECTION

ENGINE WILL NOT START

1. Weak battery

1. Charge or replace as necessary.

2. Corroded or loose battery
connections.

2. Clean and tighten battery
connections. Apply a coat of light
mineral grease to the terminals.

3. Faulty starter.

3. (Refer to 8 - ELECTRICAL/
STARTING - DIAGNOSIS AND
TESTING).

4. Faulty coil or control unit.

4. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).

5. Incorrect spark plug gap.

5. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).

6. Incorrect right bank cam timing.

6. Refer to engine timing in this
section.

7. Dirt or water in fuel system.

7. Clean system and replace fuel
filter.

8.Faulty fuel pump, relay or wiring.

8.Repair or replace as necessary.

9. Faulty cam or crank sensor

9. Refer to Ignition system.

ENGINE STALLS OR ROUGH IDLE

1. Vacuum leak.

1. Inspect intake manifold and
vacuum hoses, repair or replace as
necessary.

2. Faulty crank position sensor

2. Replace crank position sensor.

3. Faulty coil.

3. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).

9 - 2040

ENGINE - 3.7L - SERVICE INFORMATION

DR/DH

CONDITION

POSSIBLE CAUSE

CORRECTION

4. Incorrect cam timing.

4. (Refer to 9 - ENGINE/VALVE
TIMING - STANDARD
PROCEDURE).

1. ENGINE LOSS OF POWER

1. Dirty or incorrectly gapped spark
plugs.

1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).

2. Dirt or water in fuel system.

2. Clean system and replace fuel
filter.

3. Faulty fuel pump.

3. (Refer to 14 - FUEL SYSTEM/
FUEL DELIVERY/FUEL PUMP -
DIAGNOSIS AND TESTING).

4. Blown cylinder head gasket.

4. Replace cylinder head gasket.

5. Low compression.

5. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING), repair
as necessary.

6. Burned, warped or pitted valves.

6. Replace as necessary.

7. Plugged or restricted exhaust
system.

7. Inspect and replace as
necessary.

8. Faulty coil.

8. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).

9. Incorrect cam timing.

9. Refer to Engine TIming in this
section.

1. ENGINE MISSES ON
ACCELERATION

1. Spark plugs dirty or incorrectly
gapped.

1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).

2. Dirt in fuel system.

2. Clean fuel system.

3. Burned, warped or pitted valves.

3. Replcae as necessary.

4. Faulty coil.

4. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).

1. ENGINE MISSES AT HIGH
SPEED

1. Spark plugs dirty or incorrectly
gapped.

1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).

2. Faulty coil.

2. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).

3. Dirt or water in fuel system.

3. Clean system and replace fuel
filter.

DR/DH

ENGINE - 3.7L - SERVICE INFORMATION

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