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Engine Controls - Basic Testing - 2.5L: Other Mazda Millenia I

Testing & Diagnostics 7 illustrations ~1584 words

Compression

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

WARNINGDO NOT use ignition switch during compression tests on fuel injected vehicles. Use a remote starter to crank engine. Fuel injectors on many models are triggered by ignition switch during cranking, which can create a fire hazard or contaminate the engine's oiling system.
ApplicationMinimum psi (kg/cm 2 ) @ RPMStandard psi (kg/cm 2 ) @ RPM
Millenia 2.5l (1)142 (10.0) @ 250203 (14.3) @ 250
(1) Difference between cylinders should not be more than 28 psi (2.0 kg/cm 2 ).
(1)Difference between cylinders should not be more than 28 psi (2.0 kg/cm 2 ).

COMPRESSION SPECIFICATIONS

Exhaust System Backpressure

Exhaust system can be checked with a vacuum or pressure gauge. Remove Heated Oxygen Sensor (HO2S) 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 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 RELEASE

Disconnect fuel pump relay. See FUEL PUMP RELAY LOCATIONS table. Start engine (if possible) and allow to die. Turn ignition off.

ApplicationLocation
2.5LFuse/Relay Box In Left Side Of Engine Bay

FUEL PUMP RELAY LOCATIONS

Fuel Pressure Hold

  1. Disconnect negative battery cable. Install fuel pressure gauge in fuel supply line. Reconnect negative battery cable.
  2. Locate data link connector in left side of engine compartment. Connect a jumper wire between data link connector terminals F/P and GND. (Scheme 76) Turn ignition on for 10 seconds to operate fuel pump. Turn ignition off and disconnect jumper wire. Wait 5 minutes and observe fuel pressure. Fuel pressure should be at least 21 psi (1.5 kg/cm 2 ).
  3. If fuel pressure is not as specified, check fuel pump hold pressure and fuel pressure regulator hold pressure. See FUEL PUMP HOLD PRESSURE and FUEL PRESSURE REGULATOR HOLD PRESSURE headings below. Also check for injector fuel leakage. See INJECTOR FUEL LEAKAGE heading below.

Scheme 76

Scheme 76
Scheme 76

Fuel Line Pressure

  1. Disconnect negative battery cable. Install fuel pressure gauge in fuel supply line. Reconnect negative battery cable. Locate data link connector in left side of engine compartment. Connect a jumper wire between data link connector terminals F/P and GND. (Scheme 76) Turn ignition on and observe fuel line pressure. Refer to the «FUEL LINE PRESSURE»(ref-18723-S03969624172000123000000) table.
  2. If fuel line pressure is high, replace fuel pressure regulator. If fuel line pressure is low, check fuel pump maximum pressure. See FUEL PUMP MAXIMUM PRESSURE heading below. If fuel pump maximum pressure is as specified, check for plugged or restricted fuel line or fuel filter. Repair as necessary. If no problems are found, check pressure regulator hold pressure. See PRESSURE REGULATOR HOLD PRESSURE heading below.
ApplicationPressure psi (kg/cm 2 )
2.5L38-46 (2.7-3.2)

FUEL LINE PRESSURE

Fuel Pump

  1. Fuel pump is located inside fuel tank. Locate data link connector in left side of engine compartment. Connect a jumper wire between data link connector terminals F/P and GND. (Scheme 76) Remove fuel filler cap. Turn ignition on. Listen for fuel pump operation at fuel filler. Install fuel filler cap.
  2. If fuel pump does not operate, using DVOM, measure voltage between fuel pump connector power terminal and chassis ground. See the «FUEL PUMP CONNECTOR IDENTIFICATION»(ref-18723-S24020233002000123000000) table. If battery voltage is present, go to next step. If battery voltage is not present, repair power circuit to fuel pump. See appropriate wiring diagram in the «WIRING DIAGRAMS - 2.5L»(ref-18693) article.
  3. Using DVOM, check for continuity between fuel pump connector ground terminal and chassis ground. If continuity exists, replace fuel pump. If continuity does not exist, repair ground circuit.
ApplicationPower TerminalGround Terminal
MilleniaYellowBlack

FUEL PUMP CONNECTOR IDENTIFICATION

Fuel Pump Hold Pressure

  1. Disconnect negative battery cable. Disconnect fuel inlet hose at fuel rail. Install fuel pressure gauge to fuel inlet hose and plug fuel pressure gauge outlet hose. Reconnect negative battery cable.
  2. Locate data link connector in left side of engine compartment. Connect a jumper wire between data link connector terminals F/P and GND. (Scheme 76) Turn ignition on for 10 seconds to operate fuel pump. Turn ignition off and disconnect jumper wire. Wait 5 minutes and observe fuel pressure. Fuel pressure should be at least 21 psi (1.5 kg/cm 2 ). If fuel pressure is not as specified, replace fuel pump.

Fuel Pump Maximum Pressure

  1. Disconnect negative battery cable. Disconnect fuel inlet hose at fuel rail. Install fuel pressure gauge to fuel inlet hose and plug fuel pressure gauge outlet hose. Reconnect negative battery cable.
  2. Locate data link connector in left side of engine compartment. Connect a jumper wire between data link connector terminals F/P and GND. (Scheme 76) Turn ignition on for 10 seconds to operate fuel pump and observe fuel pressure. See «FUEL PUMP MAXIMUM PRESSURE»(ref-18723-S20059770412000123000000) table. Turn ignition off and disconnect jumper wire. If fuel pressure is not as specified, replace fuel pump.
ApplicationPressure psi (kg/cm 2 )
2.5L71-92 (5.0-6.5)

FUEL PUMP MAXIMUM PRESSURE

Fuel Pump Relay

  1. Locate fuel pump relay. See «FUEL PUMP RELAY LOCATIONS»(ref-18723-S33876028602000123000000) table under FUEL PRESSURE RELEASE. Using jumper wires, connect battery voltage to fuel pump relay terminal "A" (positive) and terminal "B" (negative). (Scheme 77)
  2. Check continuity between fuel pump relay terminals "C" and "D". With battery voltage connected, continuity should exist. With battery voltage disconnected, continuity should not exist. If continuity is not as specified, replace fuel pump relay.

Scheme 77

Scheme 77
Scheme 77

Fuel Pressure Regulator

  1. Disconnect negative battery cable. Install fuel pressure gauge in fuel supply line. Reconnect negative battery cable.
  2. Start and operate engine at idle. Ensure vacuum is available to pressure regulator. Observe fuel pressure with vacuum hose connected and disconnected at fuel pressure regulator. See the «REGULATED FUEL PRESSURE»(ref-18723-S37979688192000123000000) table. If fuel pressure is not as specified, check fuel pressure regulator hold pressure. See FUEL PRESSURE REGULATOR HOLD PRESSURE heading below.
Model@ Idle W/Vacuum psi (kg/cm 2 )@ Idle W/O Vacuum psi (kg/cm 2 )
2.5L30-38 (2.1-2.7)38-46 (2.7-3.2)

REGULATED FUEL PRESSURE

Fuel Pressure Regulator Hold Pressure

  1. Disconnect negative battery cable. Install fuel pressure gauge in fuel supply line. Reconnect negative battery cable.
  2. Locate data link connector in left side of engine compartment. Connect a jumper wire between data link connector terminals F/P and GND. (Scheme 76)Turn ignition on for 10 seconds to operate fuel pump. Turn ignition off and disconnect jumper wire. Carefully pinch fuel return hose close. Wait 5 minutes and observe fuel pressure.
  3. Fuel pressure should be more than 21 psi (1.5 kg/cm 2 ). If fuel pressure is not as specified, replace fuel pressure regulator.

Injector Fuel Leakage

  1. Using mechanics wire, secure each fuel injector to fuel rail. Disconnect fuel injector connectors. Remove fuel rail assembly from intake manifold. Reconnect fuel lines to fuel rail. Locate data link connector in left side of engine compartment.
  2. Connect a jumper wire between data link connector terminals F/P and GND. (Scheme 76) Turn ignition on. Tilt injectors about 60 degrees and check injector nozzles for fuel leaks. Fuel leakage should be less than one drop every 2 minutes. If fuel leakage exists, replace injector.

SPARK CHECK

Remove spark plug. Connect spark plug to high-tension lead and hold about 1/4" from ground. Crank engine and verify a strong Blue spark is discharged. If spark is not present, measure spark plug wire resistance on suspect wire. Resistance should be less than 16,000 ohms per 3.28 feet. Replace spark plug wire and spark plug as necessary.

IGNITION COIL POWER SOURCE

Turn ignition on. Using voltmeter, check for 12 volts between ignition coil positive (+) terminal and ground. If voltage is not present, check battery feed, main fuse, ignition switch and fusible links. See appropriate wiring diagram in WIRING DIAGRAMS - 2.5L article.

Scheme 78

Scheme 78: IGNITION COIL POWER SOURCE
Scheme 78: IGNITION COIL POWER SOURCE

IGNITION COIL RESISTANCE

  1. Disconnect distributor 3-pin connector. Using ohmmeter, measure primary resistance between terminals "A" and "B". (Scheme 82) Resistance should be as specified. See «IGNITION COIL RESISTANCE»(ref-18723-S31130791192000123000000) table. If resistance is not as specified, replace distributor.
  2. Remove distributor cap. Using an ohmmeter, measure secondary resistance between terminal "A" and coil tower. (Scheme 81) Resistance should be as specified. See «IGNITION COIL RESISTANCE»(ref-18723-S31130791192000123000000) table. If resistance is not as specified, replace distributor.
ApplicationPrimarySecondary
2.5L.49-.73(1) 20,000-31,000
(1) Remove distributor cap to measure secondary coil resistance.
(1)Remove distributor cap to measure secondary coil resistance.

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

Scheme 79

Scheme 79
Scheme 79

CRANKSHAFT POSITION SENSOR RESISTANCE

Disconnect crankshaft position sensor connector. Using an ohmmeter, measure the resistance between terminals "A" and "B". (Scheme 80) Resistance should be as specified. See specifications in the CRANKSHAFT POSITION SENSOR RESISTANCE table. If resistance is not as specified, replace crankshaft position sensor.

ApplicationOhms@ 68°F (20°C)
2.5L520-580

CRANKSHAFT POSITION SENSOR RESISTANCE

Scheme 80

Scheme 80
Scheme 80

CRANKSHAFT POSITION SENSOR AIR GAP

Using a feeler gauge, measure air gap between crankshaft pulley and crankshaft position sensor. (Scheme 81) Air gap should be as specified. See CRANKSHAFT POSITION SENSOR AIR GAP table. If air gap is not as specified, replace crankshaft pulley or crankshaft position sensor.

ApplicationIn. (mm)
2.5L.020-.059 (.5-1.5)

CRANKSHAFT POSITION SENSOR AIR GAP

Scheme 81

Scheme 81
Scheme 81

CAMSHAFT POSITION SENSOR VOLTAGE

  1. Remove distributor and reconnect connector. Disconnect ignition control module connector. Disconnect fuel injector connector. Turn ignition on. Connect Harness Adapter (49 T018 902) and Signal Monitor (49 9200 162A) to ECM/PCM. (Scheme 82)
  2. Set signal monitor to specified ECM/PCM terminal. Rotate distributor drive by hand and measure output voltage. Refer to the «CAMSHAFT POSITION SENSOR VOLTAGE»(ref-18723-S41427632342000123000000) table. If voltage is not as specified, check wiring harness and connectors. If harness and connectors are okay, replace distributor.
ECM/PCM Terminal (1)(2) Volts
4F (SGC Signal)5 (1 pulses/rev)
(1) See PIN VOLTAGE/PID VALUE CHARTS - 2.5L article for terminal identification. (2) Rotate sensor/distributor by hand while measuring output voltage.
(1)See PIN VOLTAGE/PID VALUE CHARTS - 2.5L article for terminal identification.
(2)Rotate sensor/distributor by hand while measuring output voltage.

CAMSHAFT POSITION SENSOR VOLTAGE

Scheme 82

Scheme 82
Scheme 82

IGNITION CONTROL MODULE

Testing information is not available from manufacturer. Check for diagnostic trouble codes. See the TESTS W/CODES - 2.5L article.

IDLE SPEED & IGNITION TIMING

Ensure idle speed and base ignition timing are set to specification. See the appropriate IDLE SPEED SPECIFICATIONS and IGNITION TIMING SPECIFICATIONS tables. If adjustment is necessary, see ADJUSTMENTS - 2.5L article.

Application (1)M/T RPM(2) A/T RPM
MilleniaN/A600-700
(1) Place automatic transmission in Park. (2) Connect a jumper wire between terminals TEN and GND at data link connector. (Scheme 76)
(1)Place automatic transmission in Park.
(2)Connect a jumper wire between terminals TEN and GND at data link connector. (Scheme 76)

IDLE SPEED SPECIFICATIONS

ApplicationM/T(1) A/T
Millenia 2.5L (2)N/A9-11 @ 650
(1) Place automatic transmission in Park. (2) Connect a jumper wire between terminals TEN and GND of data link connector. (Scheme 76)
(1)Place automatic transmission in Park.
(2)Connect a jumper wire between terminals TEN and GND of data link connector. (Scheme 76)

IGNITION TIMING SPECIFICATIONS (Degrees BTDC @ RPM)

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to the TESTS W/CODES - 2.5L article. If no hard codes are found in self-diagnostics, proceed to TESTS W/O CODES - 2.5L article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.

More articles — Engine Controls - Basic Testing - 2.5L