Engine Controls - Basic Testing: Other Mazda 626 GE

Compression

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

COMPRESSION SPECIFICATIONS

Exhaust System Backpressure

The exhaust system can be checked with a vacuum or pressure gauge. Remove O2S sensor or air injection check valve (if equipped). Connect a 0-5 psi pressure gauge and 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 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 (FUEL INJECTION)

Fuel Pressure

1. Disconnect circuit opening relay. See CIRCUIT OPENING RELAY LOCATIONS table.
2. To bleed down fuel in system, start engine (if possible) and allow to die. Connect pressure gauge to fuel line at fuel filter. Reconnect circuit opening relay.
3. Turn ignition on. Jump test connector terminals Fp and ground. If pump does not run, check fuel pump circuit and circuit opening relay.
4. If possible, start engine. Check fuel pressure with vacuum connected to and disconnected from pressure regulator. See «REGULATED FUEL PRESSURE»(ref-18324-S07782412272000123000000) table. Turn engine off and disconnect jumper wire at fuel pump check connector. Wait 10 minutes and ensure residual pressure is at least 21 psi (1.5 kg/cm 2 ).
5. Operate fuel pump by jumpering fuel pump test connector. Check fuel pump performance. Pinch hose between pressure gauge and fuel filter. DO NOT hold longer than necessary to check pressure. See «FUEL PUMP PERFORMANCE»(ref-18324-S30156430962000123000000) table. If pump does not meet specifications, check fuel pump circuits, fuel pump, fuel tank, fuel filter and repair or replace as necessary.

FUEL PUMP PERFORMANCE

REGULATED FUEL PRESSURE

Note. Fuel pump control unit terminal identification is not available.

Fuel Pump Circuit

1. Turn ignition on. Attach jumper wire to test connector terminal Fp and to ground in the diagnostic connector, next to battery.
2. Listen for fuel pump operating sound. If there is no sound, check main fuse, circuit operating relay, fuel pump and all electrical connections. PCM grounds circuit opening relay and operates fuel pump whenever distributor or crank angle sensor signals are present. On other models, airflow meter grounds circuit opening relay whenever airflow is present.
3. If circuit opening relay does not work, proceed to «SYSTEM/COMPONENT TESTS»(ref-18357) article or appropriate G - TESTS W/ CODES article in the ENGINE PERFORMANCE section below. «TESTS W/CODES - 2.0L A/T»(ref-18325) (for MX-6 2.0L) «TESTS W/CODES - 2.5L»(ref-18326) (for MX-6 2.5L) «TESTS W/CODES - 2.0L A/T»(ref-18327) (for 626 2.0L) «TESTS W/CODES - 2.5L»(ref-18328) (for 626 2.5L)

Circuit Opening Relay

1. With relay connected, ensure battery voltage is present at relay terminal Red/Black wire on 2.0L or Black/White wire on 2.5L. For locations of circuit opening relay, see CIRCUIT OPENING RELAY LOCATION table.
2. If voltages are okay, remove relay from vehicle. Using a 12-volt battery source, connect 12 volts to relay terminals "A" and "B". Ensure continuity is present across terminals "C" and "D". If continuity is not as specified, replace circuit opening relay.

CIRCUIT OPENING RELAY LOCATION

CIRCUIT OPENING RELAY CIRCUIT VOLTAGE

Scheme 1

SPARK CHECK

Check for spark at coil wire and at each spark plug wire using a high output spark tester. Check spark plug wire resistance on suspect wires. Resistance should be no less than 4878 ohms per foot.

IGNITION COIL POWER SOURCE

Turn ignition on. Using voltmeter, check for 12 volts between positive (+) terminal and ground. If no voltage is present, check battery feed, main fuse, ignition switch and fusible links.

IGNITION COIL RESISTANCE

1. Remove primary and secondary leads from ignition coil. Using ohmmeter, check primary resistance between terminals "A" and "B" of coil. (Scheme 2) Resistance should be as specified in IGNITION COIL RESISTANCE table. If resistance is not as specified, replace ignition coil.
2. Check secondary resistance between terminal "A" and coil tower. (Scheme 2) See «IGNITION COIL RESISTANCE»(ref-18324-S07446409992000123000000) table. If resistance is not within specification, replace coil.

Scheme 2

IGNITION COIL RESISTANCE

CRANK ANGLE SENSOR RESISTANCE

1. Disconnect crank angle sensor connector. Crank angle sensor is a separate unit located at front of crankshaft. Measure resistance between terminals. (Scheme 3) If resistance is not as indicated, replace crank angle sensor.
2. If ignition coil resistance and crank angle sensor test okay, check for spark. If spark is still not present, go to HALL-EFFECT SENSORS test procedure.

CRANK ANGLE SENSOR RESISTANCE

Scheme 3

HALL-EFFECT SENSORS

1. Remove distributor. Remove circuit opening relay and disconnect 3-pin connector from distributor. This will prevent coil sparking. Turn ignition on.
2. Using a voltmeter, backprobe power wire and ground wire at distributor. Voltmeter should display 12 volts. If voltage is not as specified, check ignition and ground circuits. Backprobe sensor wire at distributor. See «HALL-EFFECT SENSOR VOLTAGE SPECIFICATIONS»(ref-18324-S00542561062000123000000) table for wire colors. Slowly rotate distributor shaft one turn. Voltmeter should pulse 0-5 volts 4 times (4-cylinder) or 6 times (V6).
3. Backprobe wire on at distributor. See «HALL-EFFECT SENSOR VOLTAGE SPECIFICATIONS»(ref-18324-S00542561062000123000000) table for wire colors. Slowly rotate distributor shaft one turn. Voltmeter should pulse 0-5 volts one time. If either sensor does not work as described, turn ignition off. Disconnect 4-pin or 6-pin connector at distributor.
4. Turn ignition on. Ensure 5 volts are present at same wires which were checked in steps 2) and 3). If 5 volts are not present, check wiring and PCM. If 5 volts are present, replace distributor assembly.

HALL-EFFECT SENSOR VOLTAGE SPECIFICATIONS

IGNITOR

Testing information is not available. If coil, PCM, sensor and wiring are okay, replace ignitor.

IDLE SPEED & IGNITION TIMING

Ensure idle speed and base ignition timing are set to specification. If necessary, see ADJUSTMENTS article in the ENGINE PERFORMANCE section.

IGNITION TIMING SPECIFICATIONS

SUMMARY

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

1. «TESTS W/CODES - 2.0L A/T»(ref-18325) (for MX-6 2.0L)
2. «TESTS W/CODES - 2.5L»(ref-18326) (for MX-6 2.5L)
3. «TESTS W/CODES - 2.0L A/T»(ref-18327) (for 626 2.0L)
4. «TESTS W/CODES - 2.5L»(ref-18328) (for 626 2.5L)