Engine Controls - Basic Testing - Carbureted Honda Prelude III рестайлинг

INTRODUCTION

The following diagnostic steps will help prevent overlooking a simple problem. This is also where to begin diagnosis for a no-start condition.

The first step in diagnosing any driveability problem is verifying complaint. Test drive the vehicle under the conditions when the problem reportedly occurred.

Before entering self-diagnostics, perform a careful and complete visual inspection. Most engine control problems result from mechanical breakdowns, poor electrical connections or damaged/misrouted vacuum hoses. Before condemning the computerized system, perform each test listed in this article.

Note. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure.

VISUAL INSPECTION

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

Compression

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

Exhaust System Backpressure

The exhaust system can be checked with a vacuum or pressure gauge. Remove O2 sensor or air injection check valve (if equipped). Connect a 1-10 psi pressure gauge and run engine at 2500 RPM. If exhaust system backpressure is greater than 1 3/4-2 psi, exhaust system or catalytic converter is plugged.

If a vacuum gauge is used, connect vacuum gauge hose to intake manifold vacuum port and start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge reading 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. If fuel pump fails to run on fuel-injected models, inspect power supply to main relay. If all power supplies are present (i.e. battery, ignition and starter switch during cranking), perform functional test of main relay. See WIRING DIAGRAMS and SYSTEM/COMPONENT TESTS - CARBURETED articles.

Scheme 56

1. Disconnect fuel line from fuel tank at the engine compartment fuel filter. Connect a fuel pressure gauge to fuel line. Plug fuel filter. Remove the left side dash undercover and remove the fuel pump cut-off relay from the fuse box. (Scheme 56) Connect a jumper wire between terminals No. 1 and No. 2 in relay cavity at fuse box.
2. Turn ignition on until fuel pressure stabilizes on gauge. Turn ignition off. Gauge should indicate 1.3-2.1 psi (.09-.15 kg/cm 2 ). If pressure is less than specification, check for plugged rear fuel filter. If filter is not plugged, replace in-tank fuel pump.
3. If pressure is within specification, remove pressure gauge. Place fuel delivery line into an appropriate container. Turn ignition on and measure fuel delivery. Fuel pump should deliver at least 1.25 pints in 60 seconds. If fuel delivery does not meet specification, replace fuel pump.

Spark

Check for spark at secondary coil wire and each spark plug wire using a spark tester. If no spark is present, continue with the following tests. Check spark plug wire resistance on suspect wires. Resistance should be less than 25,000 ohms.

Ignition Coil Power Source

1. Disconnect ignition coil primary leads. (Scheme 57) Turn ignition on. Using voltmeter, check voltage between ground and Black/Yellow wire terminal of ignition coil harness.
2. Battery voltage should be present. If battery voltage is not present, check for open in Black/Yellow wire between coil and ignition switch. On some models, an in-line radio noise condenser (mounted on distributor or near coil) is utilized. If condenser shorts out, power supply will be interrupted and vehicle will not start.

Ignitor Power Source

Turn ignition off. Disconnect harness connector at distributor. Turn ignition on. Using voltmeter, check for battery voltage between ground and Black/Yellow wire of harness. If voltage is not present, check for open in Black/Yellow wire between ignition coil and harness connector. If wire is okay, check ignition coil resistance (for internal short to ground).

Note. Either a Hitachi or Toyo Denso distributor can be used on Prelude carbureted models. The Hitachi uses an internal ignitor with built-in pick-up coil windings.

Ignitor Check (Prelude Carbureted With Hitachi Distributor)

Remove distributor cap and disconnect the 2 ignitor leads. Using an ohmmeter, check for continuity between the 2 terminals. Reverse the ohmmeter leads and recheck for continuity. Continuity should exist in only one direction. If continuity exists in both directions or neither direction, replace ignitor.

Ignitor Check (Prelude Carbureted With Toyo Denso Distributor)

Check pick-up coil resistance and power sources. If no problems are found with these and a no-spark condition is present, replace ignitor.

COIL SECONDARY RESISTANCE

Scheme 57

1. Remove primary and secondary leads from ignition coil. Using an ohmmeter, check resistance between primary terminals "A" and "D" of ignition coil. (Scheme 57) Resistance should be.3-.4 ohms at room temperature. Check resistance between terminals "B" and "D" of ignition coil. Resistance should be about 2090-2310 ohms at room temperature.
2. Check secondary resistance between terminal "A" and secondary output terminal (coil tower). See «COIL SECONDARY RESISTANCE»(/honda/prelude/iii-1989-1992/remont/testing-diagnostics/#engine-controls-basic-testing-carbureted) table.
3. Check for continuity between terminals "A" and "C". Continuity should exist. Replace coil if any resistance readings were not within specification.

Pick-Up Coil Resistance Check (Prelude Carbureted With Toyo Denso Distributor)

Turn ignition off. Remove ignitor from side of distributor. Using an ohmmeter, check resistance between the 2 pin terminals closest to the vacuum advance unit on side of distributor (internal Green and Blue No. 2 wires). (Scheme 58) If resistance is not 650-850 ohms, check internal wire integrity. If wires are okay, replace pick-up coil.

Scheme 58

Note. There is no pick-up coil resistance check available for carbureted Prelude models using the Hitachi distributor with internal ignitor.

Tach Pulse Signal (Prelude Carbureted)

On carbureted models, fuel pump cut-off relay control depends on a tach signal generated on the Blue wire of the ignition coil when ignitor triggers ignition coil. If this signal is lost, fuel cut-off relay will stop fuel pump.

This signal may be verified at ECU Blue wire terminal A-1 terminal. Using a voltmeter, lightly probe terminal and check for voltage with engine cranking. If voltage is not present, repair open or short to ground in Blue wire between ECU and ignition coil.

TIMING CONTROL SENSOR USAGE

IDLE SPEED & IGNITION TIMING

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

IDLE SPEED SPECIFICATIONS (1)

IGNITION TIMING (Degrees BTDC @ RPM)

SUMMARY

If no faults were found while performing BASIC TESTING , proceed to G - TESTS W/ CODES - 2.0L PGM-CARBURETED 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 diagnosis procedures.

See also:
• WIRING DIAGRAMS
• SYSTEM/COMPONENT TESTS - CARBURETED
• ADJUSTMENTS
• G - TESTS W/ CODES - 2.0L PGM-CARBURETED
• TESTS W/O CODES
• COIL SECONDARY RESISTANCE