Engine Controls - Basic Testing: Other Mazda 626 GD

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. 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 (CARB)

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

FUEL PRESSURE (ELECTRICAL)

1. Turn ignition on. Locate fuel control unit under left side of dash. Using a jumper wire, connect terminals "B" to "D". Fuel pump (located in tank) should operate. If not, check and replace fuel pump, if necessary. Check fuel pump pressure. See «FUEL PUMP PERFORMANCE»(ref-18162-S27767171132000123000000) table. NOTE: Fuel pump control unit terminal identification is not available.
2. If fuel pump operates, remove jumper wire. With ignition on, backprobe rear of fuel pump control unit. There should be 12 volts on terminals "A" and "D" only. If not, check ignition and power feed.
3. Allow engine to idle. There should be 12 volts on terminals "A", "B", "D" and "F" only. If voltage is missing on terminal "B" only, replace fuel pump control unit. If any other terminal did not test as described, check ignition coil (tachometer signal) and power feed.

FUEL PUMP PERFORMANCE-B2200

FUEL PUMP PERFORMANCE - B2200

FUEL PUMP (MECHANICAL)

Test pump for pressure and volume. Replace as necessary.

FUEL PRESSURE (FUEL INJECTION)

1. On RX7, disconnect fuel pump connector at shock tower in trunk. On all others, disconnect circuit opening relay located behind left kick panel on B2600i, and 929. On 323 and Protege, disconnect circuit opening relay located on passenger side wall near ECU. On MX-6 and 626, located on fuse block. On Miata, disconnect circuit opening relay located under dash left of steering column. On MPV, disconnect circuit opening relay. The relay is mounted on ECU, under protective cover on passenger side floor. 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.
2. Turn ignition on. Using a jumper wire, connect terminals of Yellow fuel pump check connector together. Fuel pump check connector is located on firewall, near windshield wiper motor on B2600i, MX-6, 323 and 626, and near airflow sensor on MPV, RX7 and 929. On Miata, jumper test connector terminals Fp and ground. If pump runs, check fuel pump circuit and circuit opening relay (and fuel pump resistor on RX7).
3. If possible, start engine. Check fuel pressure with vacuum connected to and disconnected from pressure regulator. 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 ).
4. 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 table. If pump does not meet specifications, check fuel pump circuits, fuel pump, fuel tank, fuel filter or replace fuel pump.

FUEL PUMP PERFORMANCE

REGULATED FUEL PRESSURE (EXCEPT B2200)

REGULATED FUEL PRESSURE

FUEL PUMP CIRCUIT

1. Turn ignition on. Connect the terminals of Yellow fuel pump check connector with a jumper wire. Fuel pump check connector is located on firewall, under windshield wiper motor on B2600i, Miata, MPV, MX-6, and 626, and by airflow sensor on RX7 and 929. On the Protege and 323, attach jumper wire to test connector terminal Fp and to ground in the diagnostic connector located 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. On all models, airflow meter grounds circuit opening relay and operates fuel pump whenever airflow is present.
3. Circuit opening relay and fuel pump relay are controlled by the computer. For additional testing see TESTS W/CODES or SYSTEM/COMP TESTS article.

CIRCUIT OPENING RELAY

1. With relay connected, ensure specified voltage is present at relay terminals. See FUEL PUMP RELAY CIRCUIT VOLTAGES table. For locations of circuit opening relay, see CIRCUIT OPENING RELAY LOCATIONS table. CIRCUIT OPENING RELAY LOCATIONS Application Location B2600i & 929 Behind Left Kick Panel Miata Under Dash, Left Of Steering Column MPV Mounted On ECU, Under Protective Cover On Passenger Side's Floor MX-6 & 626 On Fuse Block Protege & 323 On Passenger Side's Wall, Near ECU RX7 On Bracket Behind Instrument Panel FUEL PUMP RELAY CIRCUIT VOLTAGES Terminal Ignition ON Volts Ignition START Volts Idle Volts Fp 0 12 12 Fc 12 0 0 B 12 12 12 STA 0 12 0 E1 0 0 0
2. If voltages are okay, remove relay from vehicle. Check relay operation using a 12-volt battery source and perform resistance tests. (Scheme 1)

Scheme 1

RESISTOR RELAY (RX7 ONLY)

1. Remove air cleaner and airflow meter. Disconnect fuel pump resistor. Ensure continuity exists between terminals "a" and "b". (Scheme 2)and (Scheme 3).
2. Measure resistance between the following terminals. Resistance between terminals "c" and "d" should be 60-92 ohms and between "e" and "f" should be.70-.94 ohms. If resistor relay does not test as specified, replace relay.

Scheme 2

Scheme 3

TRANSFER PUMP (PROTEGE 4WD ONLY)

Because of the rear drive shaft, the fuel tank is in two sections. A transfer pump keeps both sides of tank at equal fuel levels. An access panel is located under the rear seat. Transfer pump control unit is located under driver's seat. Disconnect the transfer pump connector at the fuel tank, and check continuity between (Black/White wire) and (Yellow wire). If no continuity is present, replace transfer pump.

Scheme 4

TRANSFER PUMP CONTROL UNIT (PROTEGE 4WD ONLY)

1. Turn ignition on. Ensure fuel gauge reads more than half full and transfer pump operation is heard. Ground transfer pump connector terminal Yellow/Blue and verify pump stops. Remove the ground from terminal Yellow/Blue and verify pump operates after about 10 seconds. If not, see TRANSFER PUMP in this article. (Scheme 4)
2. Turn ignition on. Ground fuel pump control unit terminal "M" with jumper wire. Verify that zero volts is present at control unit terminal "N". Remove the jumper wire and check that voltage is 12 volts in about 10 seconds. If not, disconnect transfer pump connector. Turn ignition on. Verify that the voltage is 12 volts at terminal "N" of the transfer pump connector. If not, replace transfer pump control unit.

SPARK

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 greater than 4888 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, main relay No. 1 (MX-6 and 626 models), injector main relay (929 models), ignition switch and fusible links.

Ignition Coil Resistance

1. Remove primary and secondary leads from ignition coil. Using ohmmeter, check primary resistance between positive and negative terminals of coil. Resistance should be as specified in «IGNITION COIL RESISTANCE»(ref-18162-S19917319222000123000000) table. If not, replace ignition coil. (Scheme 5)
2. Check secondary resistance between (positive) terminal and coil tower. See «IGNITION COIL RESISTANCE»(ref-18162-S19917319222000123000000) table. If not within specifications, replace coil.

Scheme 5

IGNITION COIL RESISTANCE (EXCEPT RX7) - Ohms @ 68°F (20°C)

RX7 IGNITION COIL/IGNITOR RESISTANCE

COIL IGNITOR POWER SOURCE (MIATA, MX-6, PROTEGE, 323, 626 TURBO & 929)

1. Ensure coil and power source are okay before checking ignitor. Disconnect coil ignitor connector. Install Ignitor Checker (49 F018 002) and Adapter Harness (49 N018 001). On Turbo models, use Adapter Harness (49 H018 910). Connect the ignitor checker and adapter between the ignitor and wiring harness, connect the power leads to the battery.
2. Turn ignition on. Disconnect the high-tension coil lead from the distributor and hold it about 1/4" from ground. Flip the SW2 on and off, and verify a strong Blue spark is discharged from lead. If spark is weak in color, replace the coil. If no spark is present, check battery feed, main fuse, main relay No. 1 (MX-6 and 626 models), injector main relay (929 models), ignition switch and fusible links. Repair or replace as necessary. CAUTION: DO NOT hold the SW2 switch on longer than one second.
3. Turn ignition on. Using voltmeter, check voltage on Black wire of adapter harness. Flip SW2 switch on and off. Verify voltmeter fluctuates. If not, replace ignitor and retest.

OPTICAL DISTRIBUTOR (B2200, B2600I, PROTEGE, 323, & MPV 2.6L)

Turn ignition on. Check optical distributor ignition source by backprobing distributor terminal for correct voltage. See OPTICAL DISTRIBUTOR VOLTAGE SPECIFICATIONS table.

OPTICAL DISTRIBUTOR VOLTAGE SPECIFICATIONS

PICK-UP COIL/IGNITOR (B2200, B2600I, MPV, MX-6 NON-TURBO & 626 NON-TUBBO)

1. Disconnect pick-up coil from distributor. Using an ohmmeter, measure resistance between 2 inner terminals on pick-up coil. Replace pick-up coil if resistance is not as specified in «DISTRIBUTOR PICK-UP COIL RESISTANCE»(ref-18162-S42063862942000123000000) table.
2. Ensure ignition coil has battery voltage. If ignition coil resistance and pick-up coil test okay, check for spark. If spark is still not available, go to TESTS W/CODES article.

DISTRIBUTOR PICK-UP COIL RESISTANCE

CRANK ANGLE SENSOR (MX-6 TURBO, 626 TURBO & 929)

1. Disconnect crank angle sensor connector from distributor. On 929, crank angle sensor is a separate unit located on the back of the camshaft. Measure resistance between terminals indicated in «CRANK ANGLE SENSOR»(ref-18162-S41313394652000123000000) table. (Scheme 6) If resistance is not as indicated, replace distributor assembly.
2. If ignition coil resistance and crank angle sensor test okay, check for spark. If spark is still not available, go to Ignitor test.

CRANK ANGLE SENSOR

Scheme 6

IGNITOR (MX-6 TURBO, 626 TURBO & 929)

1. Turn ignition off. Disconnect ignitor connector and install Test Harness (49 9200 443). Using a needle-type ohmmeter, connect (+) lead to ground and (-) lead to single-pin test wire of test harness. CAUTION: Ensure ohmmeter is installed with (+) lead to ground and (-) lead to single-pin wire of test harness. DO NOT reverse leads or damage may result.
2. Connect Ignitor Checker (49 F018 002) to other lead of test harness and to battery. (Scheme 7) Set ohmmeter to X1 scale.
3. Turn ignition on. Do not touch ignitor checker SW1 switch. Push up ignitor checker SW2 switch and note ohmmeter reading. Ohmmeter needle should jump to 1/2 of the scale and then return. If not, replace ignitor.

Scheme 7

1. Crank engine. Check for a strong Blue spark at coil wire and at each spark plug wire with a spark tester (or by holding wire 5/16" from ground). Check spark plug wire resistance on suspect wires.
2. Using ohmmeter, check resistance of high tension leads. Resistance should be 4880 ohms per foot. Disconnect and inspect all related ignition system connectors and harnesses. Clean or repair as necessary and recheck spark. If okay, go to next step.

Scheme 8

1. Disconnect 2-prong connector at ignitor. Connect voltmeter (in series) between disconnected Black/Yellow wire terminals of 2 connector halves. Turn ignition on and note voltage.
2. Voltage should be about 12 volts. Turn ignition off. Remove voltmeter and negative battery cable. Install Ignitor Checker (49 F018 002) between 2-prong connectors. (Scheme 8)
3. Disconnect Black wire from coil. Reconnect negative battery cable. Connect ohmmeter between Black wire and ground. CAUTION: Ensure negative battery cable is disconnected prior to removing Black wire from coil. DO NOT disconnect Brown wire from coil. Ensure ohmmeter leads are installed with (+) lead to ground and (-) lead to Black wire.
4. Turn ignition on. Place ohmmeter on the X1 scale. Hold ignitor checker SW2 switch on and note ohmmeter reading. Ohmmeter needle should rise to 1/3 the distance of the scale and then return. Replace ignitor if needle operation was incorrect.

LEADING SIDE COIL

Disconnect negative battery cable. Connect ohmmeter to appropriate terminals to check coil resistance. (Scheme 9) Replace coil if resistance is not.2-1.0 ohm.

Scheme 9

Scheme 10

Scheme 11

1. Disconnect 2-prong connector at ignitor. Connect voltmeter (in series) between the wire terminals of 2 connector halves. (Scheme 10) Turn ignition on and note voltage.
2. Voltage should be about 12 volts. Turn ignition off. Remove voltmeter and negative battery cable. Reconnect 2-prong connector. Disconnect 4-prong connector.
3. Install Ignitor Checker (49 F018 002) between 4-prong connectors. (Scheme 11) Disconnect Black and Blue wires from coil. Install negative battery cable. CAUTION: Ensure negative battery cable is disconnected prior to removing Black and Blue wires from coil. DO NOT disconnect Brown wire from coil. Ensure ohmmeter leads are installed with (+) lead to ground and (-) lead to Black wire.
4. Install ohmmeter between Black wire and ground. (Scheme 11) Place ignitor checker SW1 switch to the T1 position. Hold ignitor checker SW2 switch on and note ohmmeter reading. Ohmmeter needle should rise to 1/3 the distance of the scale and then return. Replace ignitor if needle operation was incorrect.
5. Turn ignition off. Disconnect ohmmeter and reconnect (+) lead to ground and (-) lead to Blue wire. CAUTION: Ensure ohmmeter is installed with (+) lead to ground and (-) lead to Blue wire. DO NOT reverse leads or damage may result.
6. Turn ignition on. Place ignitor checker SW1 switch to the T2 position. Hold ignitor checker SW2 switch on and note ohmmeter reading. Ohmmeter needle should rise to 1/3 the distance of the scale and then return. Replace ignitor if needle operation was incorrect.

TRAILING SIDE COIL

Disconnect negative battery cable. Connect ohmmeter to appropriate terminals to check coil resistance. (Scheme 9) Replace coil if resistance is not.2-1.0 ohm.

CRANK ANGLE SENSOR

Remove sensor connector. Note terminal identification. (Scheme 12) Using ohmmeter, check resistance at specified terminals. See CRANK ANGLE SENSOR RESISTANCE SPECIFICATIONS table. Ensure resistance is within specifications.

RX7 CRANK ANGLE SENSOR RESISTANCE SPECIFICATIONS

Scheme 12

IDLE SPEED & IGNITION TIMING

Ensure idle speed and base ignition timing are set to specification. If necessary, see ADJUSTMENTS article.

PISTON ENGINE IGNITION TIMING

IGNITION TIMING

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to TESTS W/CODES article. If no codes are present, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e. ROUGH IDLE, NO START, etc.).