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 engine oiling system. |
| Application | Specification |
|---|---|
| Compression Ratio | 9.0:1 |
| Compression Pressure | 171 psi (12.0 kg/cm 2 ) |
| Maximum Variation Between Cylinders | 14 psi (1.0 kg/cm 2 ) |
COMPRESSION SPECIFICATIONS
Exhaust System Backpressure
Exhaust system can be checked with a vacuum or pressure gauge. If using a pressure gauge, remove HO2S sensor. Connect a 1-5 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 using a vacuum gauge, 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, check exhaust system for restrictions.
FUEL SYSTEM
| WARNING | Always relieve fuel pressure before disconnecting any fuel injection-related component. DO NOT allow fuel to contact engine or electrical components. |
FUEL PRESSURE RELEASE
Disconnect fuel pump harness connector located under rear seat. Start engine. After engine stalls, turn ignition off. Disconnect negative battery cable. Reconnect fuel pump harness connector.
Spark (Spark Plug)
Connect spark plug to a high tension cable. Ground outer electrode (main body of spark plug), and crank engine. Spark should occur in discharge gap between electrodes. Ensure spark plug gap is .039-.043" (1.0-1.1 mm).
Ignition Coil Power Source
Disconnect coil primary connector. Turn ignition on. Using voltmeter, check voltage between positive terminal and ground. Battery voltage should exist.
Ignition Coil Resistance
- Using an ohmmeter, check primary coil resistance for cylinders No. 1 and 4 between coil connector terminals No. 1 and 3. Check resistance for cylinders No. 2 and 3 between connector terminals No. 2 and 3. (Scheme 10) See DIS IGNITION COIL RESISTANCE table.
- To check secondary coil resistance, disconnect ignition coil connector. Check resistance between coil towers No. 1 and 4 and between coil towers No. 2 and 3. See DIS IGNITION COIL RESISTANCE table. Replace coil if readings are not within specification.
| Application | Primary | Secondary |
|---|---|---|
| Sonata (2.0L) | .77-.95 | 10,300-13,900 |
DIS IGNITION COIL RESISTANCE - Ohms @ 68°F (20°C)
Scheme 10
Power Transistor (Sonata)
- Turn ignition off. Disconnect ignition coil harness connector. Connect test light (with 12-volt, 3-watt or lower bulb) between battery positive terminal and power transistor connector terminal No. 1 (Green/Yellow wire). (Scheme 11)
- Observe test light while cranking engine for 10 seconds. If test light flashes while engine is cranking, power transistor is functioning properly. If test light does not flash, replace power transistor.
Scheme 11
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 (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.