Compression
Check engine mechanical condition using a compression gauge, vacuum gauge or engine analyzer. See engine analyzer manual for specific instructions.
| WARNING | DO 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 mode, which can create a fire hazard or contaminate the engine's oiling system. |
Check engine compression with engine at normal operating temperature, all spark plugs removed and throttle wide open. See COMPRESSION SPECIFICATIONS table.
| Application | Specification |
|---|---|
| Compression Ratio | 9.7:1 |
| Compression Pressure (1) (2) | 156-185 psi (11.0-13.0 kg/cm 2 ) |
| (1) Engine cranking at 200-300 RPM with throttle open fully. (2) Maximum variation between cylinders is 28 psi (2.0 kg/cm 2 ). | |
| (1) | Engine cranking at 200-300 RPM with throttle open fully. |
| (2) | Maximum variation between cylinders is 28 psi (2.0 kg/cm 2 ). |
COMPRESSION SPECIFICATIONS
Exhaust System Backpressure
- The exhaust system can be checked with a vacuum or pressure gauge. Remove HO2S sensor or air injection check valve (if equipped).
- Connect a 1-5 psi pressure gauge and operate 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 to intake manifold vacuum port and start engine. Observe vacuum gauge. Open throttle part way and hold it steady. If vacuum gauge reading slowly drops after stabilizing, check exhaust system for restriction.
* PLEASE READ FIRST *
| WARNING | Always relieve fuel pressure before disconnecting any fuel injection-related component. DO NOT allow fuel to contact engine or electrical components. If connecting fuel pressure gauge to fuel system without using a "T" connector, DO NOT operate fuel pump for more than a few seconds. Operating fuel pump for longer than a few seconds under this condition will damage fuel pump. |
Basic diagnosis of fuel system should begin by determining fuel system pressure. If fuel pump is inoperative, see appropriate test under FUEL PUMP CIRCUIT TESTS .
RELIEVING FUEL PRESSURE
Disconnect fuel pump connector. Crank engine for at least 5 seconds. If engine starts, let it run until it stops. Reconnect fuel pump connector.
FUEL PRESSURE
Relieve fuel pressure. See RELIEVING FUEL PRESSURE . Disconnect fuel hose at pressure regulator and install fuel pressure gauge using "T" connector. Start engine and check fuel pressure at idle. See FUEL PRESSURE AT IDLE table. Verify fuel pressure increases as engine speed increases.
| Application | Vac. Line Conn. psi (kg/cm 2 ) | Vac. Line Disc. psi (kg/cm 2 ) |
|---|---|---|
| All Models | 26-30 (1.8-2.1) | 34-38 (2.4-2.7) |
FUEL PRESSURE AT IDLE
Scheme 1
- Check Fuel Pump Operation Connect test mode connector and turn ignition on. Ensure fuel pump operates for 2 seconds after turning ignition on. If fuel pump operates for 2 seconds, check fuel injector circuit. See «FUEL INJECTOR CIRCUIT TESTS»(ref-26342-S05000786992001010500000). If fuel pump does not operate, go to next step.
- Check Fuel Pump Ground Circuit Turn Ignition switch off. Disconnect connector from fuel pump. Check resistance between ground and fuel pump harness 6-pin connector terminal No. 4. (Scheme 1) If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, repair open in fuel pump ground circuit. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.
- Check Fuel Pump Power Supply Turn ignition switch on. Check voltage between ground and fuel pump 6-pin connector terminal No. 1. Voltage should be at least 10 volts. If voltage is 10 volts or more, replace fuel pump. If voltage is less than 10 volts, go to next step.
- 4) Check Harness Between Fuel Pump & Fuel Pump Relay Connector Turn ignition off. Measure resistance between harness 6-pin connector terminal No. 1 and fuel pump relay 4-pin connector terminal No. 4. Resistance should be less than one ohm. If resistance is more than one ohm, repair open in harness between fuel pump and fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article in this section. If resistance is less than one ohm, check fuel pump 6-pin connector terminal No. 1 and chassis ground. Resistance should be more than one megohm. If resistance is less than one megohm, repair short in harness between fuel pump and fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.
- Check Fuel Pump Relay Disconnect fuel pump relay and main relay connectors. Remove fuel pump relay and main relay from bracket. Connect battery voltage and ground to fuel pump relay terminals No. 1 and 3. Ensure there is less than 10 ohms resistance between terminals No. 2 and 4. If resistance is less than 10 ohms, go to next step. If resistance is greater than 10 ohms, replace fuel pump relay. (Scheme 2) See appropriate wiring diagram in WIRING DIAGRAMS article in this section. If fuel pump relay does not click, replace relay. If fuel pump relay clicks, verify zero ohms resistance between terminals No. 2 and 4. If resistance is as specified, go to next step. If resistance is not as specified, replace fuel pump relay.
- Check Harness Between ECM & Fuel Pump Relay Connector Disconnect connectors from ECM. Measure resistance of harness between ECM connector terminal No. 32 and fuel pump relay 4-pin connector terminal No. 3. Resistance should be less than one ohm. If resistance is less than one ohm, check for poor contact in ECM connector. If resistance is more than one ohm, repair open circuit in harness between ECM and fuel pump relay. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.
Scheme 2
FUEL INJECTOR CIRCUIT TESTS
Note. For fuel injector circuit tests, see appropriate TESTS W/CODES article in this section.
Note. Also see appropriate test under IGNITION CONTROL SYSTEM TESTS.
SPARK
Check for spark at spark plug wires using a spark tester. Check resistance of each spark plug wire. Replace wire if resistance is not within specification. See HIGH TENSION WIRE RESISTANCE table.
| Application | Ohms | |
|---|---|---|
| Forester | ||
| No. 1 & 3 | 6430-15,010 | |
| No. 2 & 4 | 6670-15,570 | |
| Impreza | ||
| No. 1 | 5950-13,890 | |
| No. 2 & 3 | 6240-14,560 | |
| No. 4 | 6670-15,570 | |
| Legacy | ||
| All Wires | 5120-12,340 | |
HIGH TENSION WIRE RESISTANCE
IGNITION COIL RESISTANCE
- Disconnect 3-wire connector from ignition coil assembly. Using an ohmmeter, check primary resistance between terminals No. 1 and 2 for one coil. (Scheme 3)
- Check primary resistance between terminals No. 2 and 3 for remaining coil. Resistance should be as specified. See «IGNITION COIL RESISTANCE»(ref-26342-S39824176462001010500000) table. If resistance is not as specified for each coil, replace ignition coil assembly.
- To test secondary resistance, connect ohmmeter between ignition coil secondary terminals No. 1 and 2, and terminals No. 3 and 4.
- Repeat test for other coils. If resistance of each coil is not as specified, replace ignition coil assembly.
Scheme 3
| Application | (1) Primary | (2) Secondary | |
|---|---|---|---|
| Forester & Impreza | .62-.76 | 17,850-24,150 | |
| Legacy | |||
| 2.2L | .66-.80 | 10,880-14,720 | |
| 2.5L | .40-1.00 | 18,000-24,000 | |
| (1) Checked between ignition coil primary terminals No. 1 and No. 2, and terminals No. 2 and No. 3. (Scheme 3) (2) Check between ignition coil secondary terminals No. 1 and No. 2, and terminals No. 3 and No. 4. (Scheme 3) | |||
| (1) | Checked between ignition coil primary terminals No. 1 and No. 2, and terminals No. 2 and No. 3. (Scheme 3) |
| (2) | Check between ignition coil secondary terminals No. 1 and No. 2, and terminals No. 3 and No. 4. (Scheme 3) |
IGNITION COIL RESISTANCE - OHMS @ 68°F (20°C)
IGNITION CONTROL SYSTEM TESTS
Note. Ensure battery is fully charged before performing tests.
- Check Ignition System For Proper Spark Remove spark plug wire cap from each spark plug. Install a known-good spark plug to spark plug wire and position spark plug so it is grounded to engine. Crank engine. If a spark does not occur at each spark plug go to next step. If a spark occurs at each spark plug, see «FUEL PUMP CIRCUIT TESTS»(ref-26342-S22363682862001010500000).
- Check Voltage At Ignition Coil Positive Terminal Turn ignition off. Disconnect connector from ignition coil. Turn ignition on. Ensure there is at least 10 volts between ignition coil 3-pin harness connector terminal No. 2 and ground. (Scheme 3) If voltage is as specified, go to next step. If voltage is not as specified, repair harness or connectors as necessary. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.
- Check Ignition Coil Measure primary resistance between ignition coil terminals. See «IGNITION COIL RESISTANCE»(ref-26342-S39824176462001010500000) table under IGNITION CHECKS. If resistance is not as specified, replace coil. If resistance is as specified, go to next step.
- Measure secondary resistance. See «IGNITION COIL RESISTANCE»(ref-26342-S39824176462001010500000) table under IGNITION CHECKS. If resistance is not as specified, replace ignition coil.
- Check Harness Between Ignitor & Ignition Coil Connector Turn ignition off. Disconnect connector from ignitor. Measure resistance between ignition coil connector terminal No. 5 and ignitor connector terminal No. 1 and ignition coil connector terminal No. 6 and ignitor connector terminal No. 3. Resistance should be one ohm maximum. If resistance is not as specified, repair harness or connector as necessary. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.
- Check Ignitor Input Signal Reconnect ignitor connector. Backprobe connector terminals to check voltage between ignitor connector terminal No. 1 and ground, and between ignitor connector terminal No. 2 and ground. Ensure input signal voltage fluctuates with engine speed while cranking. If no voltage, replace ignitor. If voltage is 10 volts or more, go to next step.
- Check Ignitor Ground Circuit Turn ignition off. Disconnect ignitor connector. Measure resistance between ignitor connector terminal No. 3 and engine ground. Resistance should be 5 ohms maximum. If resistance is not as specified, repair harness or connector as necessary. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.
- Check Harness Between ECM & Ignitor Connector Disconnect connector from ECM. Measure resistance of harness between ECM and ignitor. See «ECM & IGNITOR HARNESS TERMINAL IDENTIFICATION»(ref-26342-S07287201292001010500000) table. If resistance is more than one ohm, Repair open in harness between ECM and ignitor connector. See appropriate wiring diagram in WIRING DIAGRAMS article in this section. ECM & IGNITOR HARNESS TERMINAL IDENTIFICATION ECM Terminal No. Ignitor Terminal No. 41 1 40 2 94 3
- Measure resistance of harness connector between ECM connector terminal No. 41 and ground, and between ECM connector terminal No. 40 and ground. Resistance should be one megohm minimum. If resistance is less than specified, repair short to ground in harness between ECM and ignitor. See appropriate wiring diagram in WIRING DIAGRAMS article in this section. If resistance is as specified check for poor contact in ECM connector. If contact is okay, check fuel pump circuit. See «FUEL PUMP CIRCUIT TESTS»(ref-26342-S22363682862001010500000).
IDLE SPEED & IGNITION TIMING
Verify idle speed and ignition timing are set to specification. See IDLE SPEED SPECIFICATIONS and IGNITION TIMING tables. For adjustment procedures, see ADJUSTMENTS article in this section.
| Application | RPM | |
|---|---|---|
| Forester | ||
| With A/C Off | 650-750 | |
| With A/C On | 800-900 | |
| Impreza | ||
| With A/C Off | 600-800 | |
| With A/C On | 750-850 | |
| Legacy | ||
| With A/C Off | 600-800 | |
| With A/C On | 800-900 | |
IDLE SPEED SPECIFICATIONS
| Application | Auto. Trans. | Man. Trans. | |
|---|---|---|---|
| Forester | 15 @ 700 | 15 @ 700 | |
| Impreza & Legacy | |||
| 2.2L | 20 @ 700 | 14 @ 700 | |
| 2.5L | 15 @ 700 | 15 @ 700 | |
| (1) To improve stability, timing is controlled while engine is idling. Timing range is plus or minus 8 degrees (all vehicles). | |||
| (1) | To improve stability, timing is controlled while engine is idling. Timing range is plus or minus 8 degrees (all vehicles). |
IGNITION TIMING (Degrees BTDC @ RPM) (1)
Scheme 4
- Check Main Relay Turn ignition off. Remove main relay. Connect battery voltage to main relay terminals No. 1 and 2. Check resistance between main relay terminals No. 3 and 5, and terminals No. 4 and 6. (Scheme 4) Resistance should be less than 10 ohms in both tests. If resistance is as specified, go to next step. If resistance is not as specified, replace main relay.
- Check ECM Power Supply Circuit Reconnect main relay. Disconnect ECM harness connector. Turn ignition on. Using DVOM in voltmeter mode, connect DVOM negative lead to ECM harness connector No. 19. In sequence, connect DVOM positive lead to ECM harness connector terminals No. 1, 2 and 39. (Scheme 5) Voltage reading on each listed terminal should be greater than 10 volts. If voltage reading is as specified, go to next step. If voltage reading is not as specified, check and repair circuit between main relay and ECM harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.
- Check ECM Ground Circuit Turn ignition off. Disconnect ECM harness connector. Using DVOM, check resistance between chassis ground and in sequence, ECM harness connector terminals No. 17, 18, 19, 20, 42, 46, 69, 94 and 95. Resistance on each listed terminal should be less than 5 ohms. If resistance is as specified, see «IGNITION CONTROL SYSTEM TESTS»(ref-26342-S08487670782001010500000). If resistance is not as specified, check affected ground circuit between ECM harness connector or check for poor terminal contact in harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.
Scheme 5
SUMMARY
If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to appropriate TESTS W/CODES article in this section. If no hard codes are found in self-diagnostics, go to TESTS W/O CODES article in this section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.