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 | Psi (kg/cm 2 ) |
|---|---|
| Normal Compression Pressure | 170-225 (11.9-15.8) |
| Minimum Compression Pressure | 100 (7.0) |
| Maximum Variation Between Cylinders | 25 Percent |
COMPRESSION SPECIFICATIONS
FUEL PRESSURE RELEASE
| WARNING | Always release fuel pressure before disconnecting any fuel injection-related component. DO NOT allow fuel to contact engine or electrical components. |
| CAUTION | When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in the GENERAL INFORMATION section before disconnecting battery. |
- Remove rear seat cushion. Remove protector for access to fuel pump electrical connector, located on top of fuel tank. Disconnect fuel pump electrical connector from wiring harness.
- Start engine and allow engine to idle until engine stalls. Turn ignition off. Reinstall fuel pump electrical connector, protector and rear seat cushion. Fuel lines may now be disconnected. Cover fuel lines with shop towel before disconnecting, as some residual fuel pressure may exist.
FUEL PUMP RELAY
The Powertrain Control Module (PCM) controls fuel pump relay operation by controlling fuel pump relay ground circuit. PCM opens ground circuit when ignition is off, and completes ground circuit when ignition is on, to provide fuel pump operation. When ignition is first turned on, if crankshaft position sensor does not detect engine rotation, PCM de-energizes fuel pump relay after approximately one second.
Fuel pump relay receives battery voltage from fuse or fusible link depending on application. If fuel pump relay or control circuit becomes defective, a Diagnostic Trouble Code (DTC) may be stored in the PCM. See the TESTS W/CODES article. For additional information on diagnosis for fuel pump relay and control circuit, see appropriate NO START (NS) TEST in the TESTS W/CODES article.
IGNITION CHECKS
Note. For ignition system spark testing and component testing, refer to the appropriate NO TROUBLE CODE (NTC) TEST and NO START (NS) TEST in the TESTS W/CODES article.
IDLE SPEED & IGNITION TIMING
Ensure idle speed and ignition timing are set to specification. For adjustment procedures, see the ADJUSTMENTS - NON-TURBO article.
SUMMARY
If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to the TESTS W/CODES article. If no diagnostic trouble codes are found in self-diagnostics, proceed to the TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO-START, etc.) or intermittent diagnostic procedures.