Engine Controls - Basic Testing 2.4L: Other Nissan 240SX S14

Compression

Check engine mechanical condition using a compression gauge, vacuum gauge or an engine analyzer. See engine analyzer manual for specific instructions.

COMPRESSION SPECIFICATIONS

Exhaust System Backpressure

Exhaust system can be checked using a vacuum or pressure gauge. If using a pressure gauge, remove oxygen sensor or air injection check valve (if equipped). Connect a 0-5 psi pressure gauge. Run engine at 2500 RPM. If exhaust system backpressure is greater than 1 3/4 - 2 psi (.12-.14 kg/cm 2 ), exhaust system or catalytic converter is plugged.

If using a vacuum gauge, connect vacuum gauge hose to intake manifold vacuum port. Start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge reading slowly drops after stabilizing, check exhaust system for a restriction.

FUEL PRESSURE

Begin basic diagnosis of fuel system by determining fuel system pressure. If fuel pump is inoperative, check fuel pump fuse. If fuse is okay, see FUEL SYSTEM in the SYSTEM/COMPONENT TESTS article. See WIRING DIAGRAMS article for specific circuit or wire color.

1. To relieve fuel system pressure, remove fuel pump fuse. Start engine, and allow it to run until it stalls. Crank engine 2 or 3 more times to verify all pressure has dissipated.
2. Turn ignition off. Install fuel pump fuse. Connect fuel gauge between fuel filter outlet and fuel tube using a "T" connector. Disconnect electrical connector at fuel pressure regulator control solenoid valve (if equipped).
3. Start engine. Check fuel line connections for leaks. Check fuel pressure with engine idling. Disconnect vacuum hose from pressure regulator. Recheck fuel pressure.
4. Compare fuel pressure readings on pressure gauge with specifications in FUEL PRESSURE table. Release fuel system pressure as described in step 1). Disconnect fuel pressure gauge. Reconnect fuel lines. Start engine and check for fuel leaks.

REGULATED FUEL PRESSURE

DISTRIBUTOR IGNITION

To determine cause of no-spark condition, perform following tests in order given. Deviation from this procedure may cause false diagnosis and replacement of non-defective components.

Spark

Check for spark at coil wire and each spark plug wire using spark tester. DO NOT crank engine continuously for more than 2 seconds. Inspect secondary coil wire for arcing while testing spark at plugs. Check electrical connections at Camshaft Position (CMP) sensor, ignition coil and power transistor.

Ignition Coil Power Source

1. Disconnect ignition coil 2-pin connector. Turn ignition on. Check for voltage at specified wire terminal. See IGNITION COIL POWER SOURCE TERMINAL IDENTIFICATION table.
2. If voltage is present, go to POWER TRANSISTOR. If voltage is not present, check continuity of entire circuit between battery and ignition coil, including fusible link and ignition switch.

IGNITION COIL POWER SOURCE TERMINAL IDENTIFICATION

Power Transistor

For power transistor system testing, see P1320, IGNITION SIGNAL in the TESTS W/CODES article. For power transistor component testing, see IGNITION SYSTEMS in SYSTEM/COMPONENT TESTS article.

Ignition Coil Resistance

1. If ignition coil malfunction is suspected, carefully inspect external housing for burned spots indicating secondary circuit arcing to primary or ground circuits. Disconnect ignition coil primary 2-pin connector.
2. Using an ohmmeter, check resistance between primary connector terminals. Check resistance between secondary tower and positive terminal of coil primary connector. Positive terminal is identified by wire color in IGNITION COIL POWER SOURCE TERMINAL IDENTIFICATION table. If either resistance is not as specified, replace ignition coil. See appropriate IGNITION COIL RESISTANCE table.

IGNITION COIL RESISTANCE - Ohms @ 77°F (25°C)

Camshaft Position (CMP) Sensor

1. CMP sensor is located inside distributor. If a fault is present in CMP sensor, see P0340, CAMSHAFT POSITION (CMP) SENSOR in the «TESTS W/CODES»(ref-17825) article.
2. To test CMP sensor, remove distributor. Leave wiring harness connected. Using a voltmeter, connect negative lead to ground and alternately connect positive lead to 1° signal terminal and 120°/180° signal terminal. See CMP SENSOR INPUT SIGNAL TERMINALS table. See appropriate CMP sensor self-diagnostic test in the «TESTS W/CODES»(ref-17825) article.
3. Measure voltages at both terminals while rotating distributor by hand. Voltage should fluctuate between 0-5 volts. If either voltage signal does not fluctuate between 0-5 volts, check harness for short or open circuit. If no problems are found, replace CMP sensor.

CMP SENSOR INPUT SIGNAL TERMINALS

IDLE SPEED & IGNITION TIMING

Ensure idle speed and ignition timing are set to specification. Improper setting of ignition timing and idle speed may cause driveability problems and/or false setting of trouble codes. For adjustment procedures, see ADJUSTMENTS article.

IDLE SPEED & CO LEVEL

IGNITION TIMING (Degrees BTDC @ RPM)

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to the G - TESTS W/CODES article. If no hard codes are found in self-diagnostics, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.