Compression
Check engine mechanical condition with a compression gauge, vacuum gauge, or an 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. |
| Application | Specification |
|---|
| Compression Pressure |
| 1.8L Turbo |
| Normal | 145-189 psi (10.0-13.0 bar) |
| Minimum | 102 psi (7.0 bar) |
| Maximum Variation Between Cylinders | 44 psi (3.0 bar) |
| 2.8L |
| Normal | 131-203 psi (9.0-14.0 bar) |
| Minimum | 109 psi (7.5 bar) |
| Maximum Variation Between Cylinders | 44 psi (3.0 bar) |
COMPRESSION SPECIFICATIONS
Exhaust System Backpressure
The exhaust system can be tested with a vacuum or pressure gauge. If using a pressure gauge, remove 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 using a vacuum gauge, connect vacuum gauge hose to intake manifold vacuum port. Start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge indication slowly drops after stabilizing, inspect exhaust system for restriction.
FUEL SYSTEM
| WARNING | ALWAYS release fuel pressure before disconnecting fuel injection-related component. DO NOT allow fuel to contact engine or electrical components. |
FUEL PRESSURE RELEASE
Remove fuel pump relay. Start engine. Allow engine to run until it stalls. Turn ignition off. Disconnect negative battery cable. Slight pressure may remain in system. Before disconnecting any fuel system line, cover connector with a clean shop towel. Reinstall fuel pump relay.
Fuel System Pressure
- Ensure fuel pump relay is okay. Ensure correct fuel filter is installed. Ensure battery voltage is at least 12 volts. Release fuel pressure. Ensure ignition is off.
- Connect Pressure Gauge (VAG 1318) between fuel supply and fuel return lines in engine compartment. Disconnect and plug vacuum line from fuel pressure regulator. Following VAG 1551 scan tool manufacturer's instructions, energize fuel system.
- Fuel pressure should be within specification. See appropriate FUEL PRESSURE SPECIFICATIONS table. If fuel pressure is within specification, perform «FUEL SYSTEM RESIDUAL PRESSURE»(ref-3049-S05937482452000041700000) test. If fuel pressure is not within specification, check fuel pressure regulator, fuel pump and fuel lines and repair or replace as necessary.
Fuel System Residual Pressure
- Tee fuel pressure gauge into fuel supply line. Start engine and let it idle. Turn engine off. See appropriate FUEL PRESSURE SPECIFICATIONS table.
- If residual fuel pressure is minimum or more, residual fuel pressure is okay. If residual fuel pressure is less than minimum, check fuel lines for leaks and repair as necessary. Check fuel injectors for leaks. See «FUEL INJECTOR TEST»(ref-3049-S39753649912000041700000) . On 2.8L engine, check fuel pump check valve for malfunction. See «FUEL PUMP CHECK VALVE TEST»(ref-3049-S09910193032000041700000) .
| Function | Specification |
|---|
| System Pressure |
| With Engine Idling | (1) 50 psi (3.5 bar) |
| With Engine Idling | (2) 58 (4 bar) |
| Residual Pressure | (3) 36 psi (2.5 bar) |
| (1) With fuel pressure regulator vacuum hose connected. (2) With fuel pressure regulator vacuum hose disconnected. (3) After 10 minutes. |
| (1) | With fuel pressure regulator vacuum hose connected. |
| (2) | With fuel pressure regulator vacuum hose disconnected. |
FUEL PRESSURE SPECIFICATIONS (1.8L TURBO)
| Function | Specification |
|---|
| System Pressure |
| With Engine Idling | (1) 55-61 psi (4.0-4.2 bar) |
| With Engine Idling | (2) 48-54 (3.3-3.7 bar) |
| Residual Pressure |
| Cold Engine | (3) 32 psi (2.2 bar) |
| Warm Engine | (3) 44 psi (3.0 bar) |
| (1) With fuel pressure regulator vacuum hose disconnected. (2) With fuel pressure regulator vacuum hose connected. (3) After 10 minutes. |
| (1) | With fuel pressure regulator vacuum hose disconnected. |
| (2) | With fuel pressure regulator vacuum hose connected. |
FUEL PRESSURE SPECIFICATIONS (2.8L)
2.8L
- Connect Pressure Gauge (VAG 1318) between fuel supply and fuel return lines in engine compartment. Ensure pressure gauge test valve is in OPEN position.
- Operate remote control switch for approximately 30 seconds. Move pressure gauge test valve to CLOSED position. Briefly operate remote control switch until maximum of 80 psi (5.5 bar) is indicated. Observe pressure drop on fuel pressure gauge.
- After 10 minutes, maximum allowable pressure drop is 7 psi (.5 bar). If pressure drop is more than allowable maximum, ensure no fuel leaks are present in fuel lines. If no fuel leaks are present in fuel lines, fuel pump check valve is defective. Replace fuel pump.
IDLE SPEED & IGNITION TIMING
Idle speed, ignition timing and ignition timing advance are controlled by the PCM and are not adjustable.
SUMMARY
If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to appropriate SELF-DIAGNOSTICS article. If no hard codes are found in self-diagnostics, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.
