Compression
Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer manual for specific instructions. Ensure electrical connector is disconnected from ignition coil to prevent engine from starting when performing compression test.
| 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 (kPa) |
|---|---|
| Normal Compression Pressure | 178 (1227) |
| Minimum Compression Pressure | 100 (690) |
| Maximum Variation Between Cylinders | (1) |
| (1) Maximum variation is 25 percent. | |
| (1) | Maximum variation is 25 percent. |
COMPRESSION SPECIFICATIONS
FUEL SYSTEM 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 GENERAL INFORMATION before disconnecting battery. |
- Disconnect electrical connector at injector. Connect jumper wire between Dark Green/Orange wire electrical terminal on injector and positive battery terminal.
- Momentarily connect jumper wire between remaining electrical terminal on injector and ground for no longer than 5 seconds. DO NOT exceed 5 seconds or injector may be damaged. This operates injector and releases fuel pressure.
- Wait 5 seconds and then ground jumper wire for another 5 seconds. Remove jumper wires. Install electrical connector. Fuel pressure should now be released. Use care when disconnecting fuel lines, as some fuel pressure may still exist in fuel lines.
FUEL PUMP RELAY
Fuel pump relay is used to provide voltage to fuel pump. Fuel pump relay is located in power distribution center at driver's side front corner of engine compartment, near the battery. Fuel pump relay receives constant battery voltage at one side of relay from fuse No. 13 (20-amp) in power distribution center. When ignition is on, fuel pump relay receives voltage at the other side of the relay from Positive Temperature Coefficient (PTC) No. 1 in junction block located behind driver's side of instrument panel, to the left of steering column. PTC is a specified amperage solid-state circuit breaker. The Powertrain Control Module (PCM) controls the ground circuit for fuel pump relay. When ignition is on, PCM completes ground circuit for fuel pump relay and voltage is supplied to the fuel pump. If crankshaft position sensor does not detect engine rotation, the PCM opens the ground circuit and de-energizes the fuel pump.
If fuel pump relay or control circuit failure exists, a Diagnostic Trouble Code (DTC) may be stored in the PCM. See appropriate TESTS W/CODES - 3.0L article. For additional information on diagnosis for fuel pump relay and control circuit, see appropriate NO START (NS) TEST in TESTS W/CODES - 3.0L article.
IGNITION CHECKS
Note. For ignition system spark testing and component testing, see appropriate NO TROUBLE CODE (NTC) TEST and NO START (NS) TEST in TESTS W/CODES - 3.0L article.
IDLE SPEED & IGNITION TIMING
Idle speed and ignition timing is controlled by Powertrain Control Module (PCM) and is nonadjustable.
SUMMARY
If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to TESTS W/CODES - 3.0L article. If no diagnostic trouble codes are found in self-diagnostics, proceed to appropriate TESTS W/O CODES - 3.0L article for diagnosis by symptom (i.e., ROUGH IDLE, NO-START, etc.) or intermittent diagnostic procedures.