Engine Controls - Basic Testing: Other Infiniti J30 I

Compression

Check engine compression at normal operating temperature at specified cranking speed. Release fuel pressure. See FUEL SYSTEM. Disconnect crankshaft position sensor harness connector. Remove all spark plugs. Depress accelerator pedal fully to hold throttle valve wide open. See COMPRESSION SPECIFICATIONS table.

Note. If cylinder compression in one or more cylinders is low, repeat inspection using a small amount of oil poured into each cylinder. If compression pressure increases, piston rings may be worn or damaged. If compression pressure does not increase, a valve may be sticking or seating improperly. If compression in any 2 adjacent cylinders is low and does not change after oil is added, there is a leak past head gasket. Make repairs as needed and reinspect.

COMPRESSION SPECIFICATIONS (1)

Exhaust System Backpressure

Exhaust system can be checked with a vacuum gauge or a pressure gauge. Remove HO2S sensor. Connect a 1-10 psi (.07-.70 kg/cm 2 ) pressure gauge, and run engine at 2500 RPM. If exhaust system backpressure is greater than 1.75-2.00 psi (.12-.14 kg/cm 2 ), exhaust system or catalytic converter is plugged.

If a vacuum gauge is used, connect it to intake manifold vacuum. Observe vacuum gauge reading at idle. Open throttle part way (about 2500 RPM) and hold steady. If vacuum gauge slowly drops after stabilizing, exhaust system should be checked for a restriction.

FUEL PRESSURE

Basic diagnosis of fuel system should begin with determining fuel system pressure.

Relieving Fuel Pressure

To relieve pressure, remove fuel pump fuse, start engine and allow to run until engine stalls due to lack of fuel. Crank engine 2-3 more times to verify all pressure has dissipated.

Checking Fuel Pressure

1. Disconnect fuel hose on fuel filter outlet side and install fuel pressure gauge. Replace pump fuse. Start engine and check fuel line connections for leakage. Check fuel pressure with engine idling. Record fuel pressure gauge reading.
2. Disconnect and plug vacuum hose from pressure regulator and immediately note fuel pressure. Record fuel pressure gauge reading. See FUEL PRESSURE table.
3. Connect a hand-held vacuum pump to fuel pressure regulator. Start engine and watch fuel pressure gauge as vacuum is changed. Fuel pressure should decrease as vacuum increases. If result is not as specified, replace fuel pressure regulator.

FUEL PRESSURE

DISTRIBUTORLESS IGNITION SYSTEM CHECKS

To determine cause of a no-spark condition, following steps must be performed in order given. Deviation from this procedure may cause false diagnosis and replacement of non-defective components.

Ignition Coil Power Source

1. Turn ignition off. Disconnect ignition coil relay harness connector. Turn ignition on. Connect negative voltmeter lead to ground. Connect positive lead to one harness Yellow/Black wire and then to the other Yellow/Black wire. Battery voltage should be present on both terminals.
2. If battery voltage is not present, check harness continuity between ECCS relay and EFI harness connector (Yellow/Black wire) and 7.5-amp fuse in fuse box. Repair or replace as necessary.

Ground Circuit

1. Turn ignition off. Disconnect ECM harness connector. Check continuity between engine ground and ECM harness connector terminals No. 10, 20, 50, 60, 107, 108 and 116 (Black wires). Continuity should be present. If continuity is not present, repair harness or connector.
2. Disconnect power transistor unit harness connector. Check continuity between Black wire on harness connectors and ground. Continuity should be present. If continuity is not present, check harness connector between power transistor unit and engine ground.

Output Signal Circuit

1. Turn ignition off. Disconnect ECM and ignition coil relay harness connectors. Check continuity between ECM terminal No. 16 (harness side) and ignition coil relay connector terminal No. 1 (Gray/Red wire). See WIRING DIAGRAMS article. If continuity is present, go to next step. If continuity is not present, check harness and connectors between ECM and ignition coil relay. Repair as necessary and repeat step 1).
2. Check harness continuity between ECM and ignition coil in each cylinder. (Scheme 50) Continuity should be present. If continuity is not present, repair or replace harness or connectors.

Scheme 50

Ignition Coil Resistance

Disconnect ignition coil harness connector. Using ohmmeter, check resistance between coil terminals No. 1 and 2. Resistance should be approximately.9 ohm. If resistance is not as specified, replace ignition coil. (Scheme 51)

Scheme 51

Power Transistor

Disconnect power transistor harness connector. Using ohmmeter, check power transistor continuity. (Scheme 52) Replace power transistor if results are not as specified.

Scheme 52

Power Transistor Relay

1. Connect a 12-volt power source and ground to terminals No. 1 and 2 of relay. (Scheme 53) Using ohmmeter, check continuity between terminals No. 3 and 5. Continuity should exist while relay is energized.
2. Disconnect power source and recheck continuity across terminals No. 3 and 5. No continuity should exist. If continuity exists, check harness and connectors. If harness and connectors are okay, replace power transistor relay.

Scheme 53

Camshaft Position Sensor

1. Remove camshaft position sensor from engine. DO NOT disconnect camshaft position sensor harness connector. Turn ignition on (engine off).
2. Connect negative lead of an analog voltmeter to ground. Rotate camshaft position sensor shaft slowly by hand. Connect positive voltmeter lead to camshaft position sensor connector terminal No. 1 (one-degree signal). Voltage should fluctuate between zero and 5 volts. Move voltmeter positive lead to terminal No. 2 (120-degree signal). Voltage should again fluctuate between zero and 5 volts. (Scheme 54)

Scheme 54

IDLE SPEED & IGNITION TIMING

Ensure idle speed and ignition timing are set to specification. For adjustment procedures, see ADJUSTMENTS article.

IDLE SPEED

IGNITION TIMING (Degrees BTDC @ RPM)

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to 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.