Basic Testing - v6 Mazda MPV V

INTRODUCTION

Note. The following diagnostic steps are here to prevent overlooking a simple problem. This is also the place to start diagnosis for a "NO-START" condition.

The first step in diagnosing any driveability problem is to verify that the problem exists. This may be accomplished by test driving the vehicle under the conditions during which the problem reportedly occurs.

Prior to entering self-diagnostics, a careful and complete inspection of several systems is required. Most driveability or "no start" problems are not related to computerized engine control systems, but are in fact simple mechanical, electrical, fuel or vacuum related faults. Most engine control problems are the result of mechanical breakdowns, poor electrical connections, damaged or misrouted vacuum hoses.

Before considering the computer system as a possible cause of problems, ignition high tension wires, fuel supply, electrical connections and vacuum hoses should be checked. Failure to do so may result in improper diagnosis or lost diagnostic time.

VISUAL INSPECTION

Perform a visual inspection of all electrical wiring. Look for chafed, stretched, cut or pinched wiring. Inspect electrical connectors and connections for tight fit and corrosion. Repair as necessary. Inspect all vacuum hoses for proper routing, cuts or pinches. If necessary, see VACUUM DIAGRAMS article in the ENGINE PERFORMANCE Section to verify routing and connections. Repair as necessary. Inspect air induction system for possible vacuum leaks, obstructions in air cleaner (ice, mud, etc.) or problems with turbocharger, if equipped.

COMPRESSION

Engine mechanical condition can be checked using a compression gauge, vacuum gauge, or an engine analyzer capable of performing a relative compression test. See engine analyzer instruction manual for availability and description of relative compression feature.

EXHAUST SYSTEM BACKPRESSURE

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

If a vacuum gauge is used, connect it to intake manifold vacuum. Start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge slowly drops after stabilizing, exhaust system should be checked for a restriction.

Fuel Pressure (Electrical)

1. Turn ignition on. Locate fuel control module 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 at tank, if necessary. Check fuel pump pressure. See FUEL PUMP SPECIFICATIONS table. NOTE: Fuel pump controller 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 (Mechanical)

Test pump for pressure and volume. Replace as necessary.

FUEL INJECTION MODELS

Fuel Pressure

1. On all V6 models, disconnect circuit opening relay (located behind left kick panel on 929). On MPV, relay is mounted on ECU. ECU is under protective cover on passenger side floor. Start engine (if possible) and allow to die. Connect pressure gauge to fuel line at fuel filter.
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 airflow sensor on MPV and 929. If pump runs, check fuel pump circuit and circuit opening relay.
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 - AT IDLE

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, by airflow sensor on MPV and 929.
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 MPV and 929 models, airflow meter grounds circuit opening relay and operates fuel pump whenever air flow is present.
3. Circuit opening relay and fuel pump relay on MPV are controlled by the computer. For additional testing see TESTS W/CODES or SYSTEM/COMPONENT TESTS article in the ENGINE PERFORMANCE section.

Circuit Opening Relay

1. With relay connected, ensure specified voltage is present at relay terminals. See FUEL PUMP RELAY CIRCUIT VOLTAGES table. Circuit opening relay on 929 is behind the driver's side kick panel. On MPV, relay is mounted on ECU. ECU is under protective cover on passenger side floor. FUEL PUMP RELAY CIRCUIT VOLTAGES Terminal Ignition "ON": Volts Ignition "OFF" 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 making resistance tests. (Scheme 5)

Scheme 5

Spark

1. Crank engine. Check for a strong Blue spark at coil wire (if applicable) and at each spark plug wire by using a low voltage spark tester (or holding wire 5/16" from ground). Ensure spark plug wire resistance of each wire is 4880 per foot.
2. Disconnect and inspect all related ignition system connectors and harness. Clean or repair as necessary and recheck SPARK. If still no spark, go to next step.

Ignition Coil Power Source

Disconnect primary wires at ignition coil. Turn ignition on. Using voltmeter, check voltage between coil positive terminal and ground of each ignition coil. Battery voltage should exist. If not, check battery feed, injector main relay (929 models), ignition switch and fusible links.

Coil Ignitor Power Source (MPV (3.0L) & 929)

Disconnect coil ignitor connector. Turn ignition on. Using voltmeter, check voltage between positive terminal (see WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section for wire color) and ground. Battery voltage should exist. If not, check battery feed, injector main relay (929 models), ignition switch and fusible links.

Ignition Coil Resistance

1. Inspect coil for signs of arcing or leakage. Remove primary and secondary leads from ignition coil. Using ohmmeter, check primary resistance between (positive) and (negative) terminals of coil. (Scheme 6)
2. Check secondary resistance between (positive) terminal and coil tower. See V6 IGNITION COIL RESISTANCE table. Replace coil if readings are not within specifications.

Scheme 6

V6 IGNITION COIL RESISTANCE

Pick-Up Coil (MPV)

1. Disconnect pick-up coil from distributor. Using an ohmmmeter, measure resistance between 2 inner terminals. Replace pick-up coil if resistance is not as specified in DISTRIBUTOR PICK-UP COIL RESISTANCE 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 SELF-DIAGNOSTIC TROUBLE CODES.

DISTRIBUTOR PICK-UP COIL RESISTANCE

Crank Angle Sensor (929)

Disconnect crank angle sensor connector from distributor. Measure resistance between terminals indicated in CRANK ANGLE SENSOR table. (Scheme 7) 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 next test.

CRANK ANGLE SENSOR

Scheme 7

Ignitor (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 8) 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 8

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.

V6 IDLE SPEED & IGNITION TIMING (DEGREES BTDC @ RPM)

SUMMARY

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

See also:
• CRANK ANGLE SENSOR