Engine Controls - Basic Testing - 3.5L: Diagnosis Chrysler LHS I

VISUAL INSPECTION

Visually inspect all electrical wiring, looking for chafed, stretched, cut or pinched wires. Ensure electrical connectors fit tightly and are not corroded. Ensure vacuum hoses are properly routed and are not pinched or cut. See VACUUM DIAGRAMS article to verify routing and connections (if necessary). Inspect air induction system for possible vacuum leaks.

Checking Fuel Pressure (Vehicles With Fuel Rail Test Port)

1. Relieve fuel pressure. On vehicles with vacuum assisted fuel pressure regulators, disconnect vacuum hose from fuel pressure regulator before checking fuel pressure. Remove fuel rail test port protective cap. Connect Fuel Pressure Gauge (C-4799) to fuel rail test port. CAUTION: DO NOT activate fuel pump for long periods, or engine may hydrostatically (liquid) lock.
2. Turn ignition switch to ON position. Using Diagnostic Readout Box (DRB), select ASD FUEL SYSTEM TEST mode. In this mode, DRB energizes Auto Shutdown (ASD) relay, causing fuel pump to activate and pressurize fuel system.
3. Note fuel pressure, and record reading. Deactivate fuel pump. Relieve fuel pressure. Remove fuel pressure gauge. Reactivate fuel pump. Ensure fuel does not leak from fuel rail test port. Deactivate fuel pump. Install fuel rail test port protective cap.
4. If fuel pressure is within specification, fuel system is functioning properly and further testing is not required. See «FUEL SYSTEM PRESSURE SPECIFICATIONS»(ref-11035-S26876064482000111000000) table. If fuel pressure is greater than specification, go to step 7). If fuel pressure is less than specification, install Fuel Pressure Gauge (C-4799) and appropriate fuel pressure test adapter in fuel supply line between fuel tank and fuel filter.
5. Using DRB, repeat ASD FUEL SYSTEM TEST. If fuel pressure is at least 5 psi greater than fuel pressure recorded in step 3), replace fuel filter. If no change in fuel pressure is observed, gently squeeze fuel return hose.
6. If fuel pressure increases while squeezing fuel return hose, replace fuel pressure regulator. If fuel pressure does not change while squeezing fuel return hose, check for plugged fuel inlet strainer or defective fuel pump. Repair as necessary.
7. Remove fuel return hose from fuel pump at fuel tank. Connect fuel pressure test adapter to return hose. Place other end of adapter into an approved gasoline container (minimum 2 gallon size).
8. Turn ignition switch to ON position. Repeat ASD FUEL SYSTEM TEST. If fuel pressure is now correct, replace fuel pump assembly. See FUEL SYSTEM PRESSURE SPECIFICATIONS table. If pressure is still greater than specification, deactivate fuel pump. Remove fuel pressure test adapter, and connect fuel pump return hose.
9. Disconnect fuel return hose from chassis fuel lines at engine. Connect fuel pressure test connector adapter to fuel return hose. Place other end of hose in approved gasoline container. Repeat ASD FUEL SYSTEM TEST.
10. If fuel pressure is now correct, check for restricted fuel return line. If no change is observed, replace fuel pressure regulator.

FUEL SYSTEM PRESSURE SPECIFICATIONS

Checking Fuel Pressure (Vehicles Without Fuel Rail Test Port)

1. Relieve fuel pressure. On vehicles with vacuum assisted fuel pressure regulators, disconnect vacuum hose from fuel pressure regulator before checking fuel pressure.
2. On all vehicles, disconnect fuel supply hose from chassis lines at engine. Connect Fuel Pressure Gauge (C-4799) to appropriate fuel pressure test adapter. Install adapter between fuel supply hose and chassis fuel line. CAUTION: DO NOT activate fuel pump for long periods, or engine may hydrostatically (liquid) lock.
3. Turn ignition switch to ON position. Using Diagnostic Readout Box (DRB), select ASD FUEL SYSTEM TEST mode. In this mode, DRB energizes Auto Shutdown (ASD) relay, causing fuel pump to activate and pressurize fuel system.
4. Note fuel pressure, and record reading. Stop ASD FUEL SYSTEM test mode. Relieve fuel pressure. Remove fuel pressure gauge. If fuel pressure is within specification, fuel system is functioning properly and further testing is not required. See «FUEL SYSTEM PRESSURE SPECIFICATIONS»(ref-11035-S26876064482000111000000) table.
5. If fuel pressure is greater than specification, go to step 8). If fuel pressure is less than specification, install Fuel Pressure Gauge(C-4799) and fuel pressure test adapter in fuel supply line between fuel tank and fuel filter.
6. Repeat ASD FUEL SYSTEM TEST. If fuel pressure is at least 5 psi greater than fuel pressure recorded in step 4), replace fuel filter. If no change is observed, gently squeeze fuel return hose.
7. If fuel pressure increases while squeezing fuel return hose, replace fuel pressure regulator. If fuel pressure does not change while squeezing fuel return hose, problem may either be a plugged fuel inlet strainer or defective fuel pump. Repair as necessary.
8. Disconnect fuel return hose from fuel pump at fuel tank. Connect appropriate fuel pressure test adapter to fuel return hose. Place other end of adapter into an approved 2 gallon gasoline container.
9. Turn ignition switch to ON position. Repeat ASD FUEL SYSTEM TEST. If pressure is now correct, replace fuel pump assembly. See «FUEL SYSTEM PRESSURE SPECIFICATIONS»(ref-11035-S26876064482000111000000) table. If pressure is still greater than specification, deactivate fuel pump. Remove fuel pressure test adapter, and connect fuel pump return hose.
10. Disconnect fuel return hose from chassis fuel lines at engine. Connect fuel pressure test connector adapter to fuel return hose. Place other end of hose in an approved gasoline container. Repeat ASD FUEL SYSTEM TEST.
11. If pressure is now correct, check for restricted fuel return line. If no change is observed, replace fuel pressure regulator.

Spark Test

1. Remove spark plug cable from cylinder No. 2. Insert a known-good spark plug into spark plug cable. Ground spark plug on engine. Crank engine and check for spark. Repeat procedure at remaining cylinders.
2. If no spark or an irregular, weak spark is present at one or more spark plug cables, go to IGNITION CABLE RESISTANCE TEST. If no spark is present, go to NO-START TEST.

Ignition Cable Resistance Test

Remove ignition cables, and measure their resistance (3000-12,000 ohms per foot). Replace cable(s) if cable resistance is not as specified. If resistance is as specified, go to IGNITION COIL RESISTANCE TEST.

Ignition Coil Resistance Test

1. Disconnect ignition coil harness connector. Measure primary coil resistance between battery voltage terminal and pin corresponding to cylinder(s) in question. (Scheme 14)
2. Measure secondary coil resistance between coil towers of grouped cylinders; No. 1 and 4, 2 and 5, and 3 and 6. Replace ignition coil if primary/secondary coil resistance is not as specified. See IGNITION COIL RESISTANCE table under IGNITION COIL.

No-Start Test

1. Ensure battery is fully charged (at least 12.6 volts). Disconnect coil electrical connector. Connect a test light to coil electrical connector battery voltage terminal. (Scheme 14)
2. Turn ignition switch to ON position. Test light should momentarily flash on and off. If test light does not momentarily flash on and off, ASD relay has failed to energize. Check ASD relay and related circuits. See appropriate «TESTS W/CODES - 3.5L»(ref-11020) article.
3. If test light momentarily flashes on and off, PCM has grounded Auto Shutdown (ASD) relay. Go to next step. DO NOT turn ignition off at this time.
4. Crank engine, and observe test light. If ignition was turned off at end of step 3), turn ignition switch to ON position, wait for test light to flash once, and then crank engine.
5. If test light momentarily flashes during cranking, engine controller is not receiving a camshaft sensor signal. Check camshaft sensor and related sensor circuits. See «TESTS W/CODES - 3.5L»(ref-11020) article.
6. If test light does not flash during cranking, disconnect camshaft sensor connector. Turn ignition switch to OFF and then to ON position. Wait for test light to momentarily flash once, and then crank engine.
7. If test light momentarily flashes, camshaft sensor is shorted and must be replaced. If test light does not flash, no-start condition is caused by problem in crankshaft or camshaft sensor 9-volt power supply circuit or by crankshaft sensor 5-volt output or ground circuits. See appropriate «TESTS W/CODES - 3.5L»(ref-11020) article.

Scheme 14

See SPARK TEST under OPTICAL IGNITION SYSTEM .