Compression
Engine mechanical condition can be checked with a compression gauge, vacuum gauge, or engine analyzer. See engine analyzer instruction manual for specific instructions. Lowest compression reading must not be less than 75 percent of highest reading.
| CAUTION | DO NOT use ignition switch during compression tests on vehicles with fuel injection. Fuel injectors are triggered by ignition switch during cranking mode. Use a remote starter to crank engine to prevent fire hazard and contamination of catalytic converter and engine oiling system. |
Exhaust System Backpressure
Exhaust system backpressure can be checked with a vacuum gauge or a 0-5 psi pressure gauge. If a pressure gauge is used, remove Oxygen Sensor (O2S). Connect gauge to O2S port. Start and run engine at 2500 RPM. If backpressure is more than 2 psi, exhaust system is plugged. If a vacuum gauge is used, connect it to intake manifold vacuum port. Start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge drops slowly after stabilizing, inspect exhaust system for a restriction.
FUEL PRESSURE
| WARNING | ALWAYS relieve fuel pressure before disconnecting any fuel injection system component. DO NOT allow fuel to contact engine or electrical components. |
Note. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article.
Fuel Pressure Release
Start engine. Unplug fuel pump relay connector, located behind left side of instrument panel. Allow engine to stall. Fuel pressure is now relieved.
Scheme 18
- Connect fuel pressure gauge between fuel filter and fuel rail. Open main valve and close drain valve. Locate fuel pump test connector in engine compartment. Test connector is terminal No. 22 of Data Link Connector, located behind battery, at left shock tower. (Scheme 18)
- Connect jumper wire between fuel pump test terminals. Turn ignition on. If pump does not run, check fuel pump circuit. If possible, start engine. Measure and record fuel pressure. See «FUEL PUMP PERFORMANCE»(ref-23408-S32138691652001010300000) table. Disconnect vacuum from pressure regulator. Turn engine off. Wait 5 minutes. Verify residual pressure is at least 21 psi (1.5 kg/cm 2 ).
- Operate fuel pump by reconnecting jumper wire at fuel pump test connector. Check fuel pump performance. Pinch hose between pressure gauge and fuel filter. DO NOT pinch hose longer than necessary to measure pressure. See «FUEL PUMP PERFORMANCE»(ref-23408-S32138691652001010300000) table. If pump does not meet specifications, inspect fuel pump circuit, fuel pump, fuel tank, and fuel filter.
| Application | Specification |
|---|---|
| Pressure | (1) |
| Volume | (2) |
| (1) For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. (2) Minimum volume in 10 seconds is 5.5 ounces (167 cc) | |
| (1) | For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. |
| (2) | Minimum volume in 10 seconds is 5.5 ounces (167 cc) |
FUEL PUMP PERFORMANCE
Fuel Pump Circuit
- Turn ignition on. Connect jumper wire between fuel pump test connector terminal and ground. Test connector is terminal No. 22 of Data Link Connector, located behind battery, at left shock tower. (Scheme 18) Turn ignition on to activate fuel pump.
- Listen for fuel pump sound. If there is no sound, inspect main fuse, inertia switch (located at left rear of passenger compartment), fuel pump relay, fuel pump, and all electrical connections.
Fuel Pump Relay
Remove fuel pump relay, located under left side of instrument panel. Continuity should not exist between terminals "A" and "C". (Scheme 19) Using fused jumper wires, apply 12 volts to relay terminals "E" and "F". Continuity should exist between terminals "A" and "C". Replace relay if operation is not as specified.
Scheme 19
FIRING ORDER
Check spark plug wire routing. Firing order is 1-3-4-2.
SPARK
- Crank engine. Check for a strong Blue spark at each spark plug wire by using a high output spark tester. Verify resistance of each spark plug wire is 4000-7000 ohms per foot.
- Unplug and inspect all related ignition system connectors and harness. Clean or repair as necessary, and recheck spark. If still no spark, go to «IGNITION COIL POWER SOURCE»(ref-23408-S15115240762001010300000) .
IGNITION COIL POWER SOURCE
Unplug connector at ignition coil. Turn ignition on. Measure voltage between Blue primary wire on harness connector and ground. If battery voltage does not exist, inspect battery feed, ignition switch, and fusible links. If battery voltage exists, go to IGNITION COIL RESISTANCE .
IGNITION COIL RESISTANCE
Measure resistance between primary terminals of coil. Measure resistance between positive primary terminal and high voltage terminal. (Scheme 20) See IGNITION COIL RESISTANCE table. Insulation resistance between coil case and primary positive terminal should be infinite. Replace coil if resistance measurements are not within specification.
| Application | Primary (Ohms) | Secondary (Ohms) |
|---|---|---|
| Aspire | 0.5-0.7 | 20,000-31,000 |
IGNITION COIL RESISTANCE
Scheme 20
IDLE SPEED & IGNITION TIMING
Ensure idle speed and ignition timing are set to specification. For adjustment procedures, see ADJUSTMENTS article.
SUMMARY
If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to TESTS W/CODES article. If no hard codes are found in self-diagnostics, proceed to TESTS W/O CODES article for diagnosis by symptom (ROUGH IDLE, NO START, etc.) or diagnostic procedures for intermittent problems.