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 | 178 (12.5) |
| Minimum Compression Pressure | 100 (7.0) |
| Maximum Variation Between Cylinders | (1) |
| (1) Maximum variation between cylinders is 25 percent. | |
| (1) | Maximum variation between cylinders is 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. |
Scheme 108
- Fuel pressure is released by energizing fuel injectors. DO NOT attempt to start engine for several minutes after releasing fuel pressure, as to prevent hydrostatic lock.
- Disconnect fuel injector harness connector. (Scheme 108) Connect jumper wire between Dark Green/Orange wire on fuel injector side of fuel injector harness connector and positive battery terminal.
- Connect another jumper wire to any remaining electrical terminal on fuel injector harness connector. All wires, except Dark Green/Orange wire (power wire) in the fuel injector harness connector are ground circuits for individual fuel injectors. CAUTION: DO NOT apply battery voltage to fuel injector for extended periods or fuel injector may be damaged.
- Momentarily touch remaining end of jumper wire to ground in short intervals to release fuel pressure. Repeat grounding procedure by operating 2 more fuel injectors to ensure fuel pressure is released.
- Remove jumper wires. Reinstall fuel injector harness connector. Fuel lines may now be disconnected. Cover fuel lines with shop towel before disconnecting, as some residual fuel pressure may exist.
Scheme 109
- Disconnect negative battery cable. Release fuel pressure. See «FUEL PRESSURE RELEASE»(ref-24887-S36273657042001010500000) under FUEL SYSTEM.
- Disconnect chassis fuel supply line from fuel line at front of fuel rail. To disconnect chassis fuel supply line, squeeze retaining tabs together on fuel line quick-connector fitting, and pull fuel line quick-connector fitting from fuel supply line.
- Connect Fuel Pressure Gauge (C-4799) to Adapter (6539). Install fuel pressure gauge and adapter between chassis fuel supply line and fuel line at front of fuel rail. Ensure all fitting are securely connected.
- Connect scan tool to Data Link Connector (DLC), located below driver's side of instrument panel. (Scheme 109) Turn ignition on.
- Using scan tool, actuate ASD fuel system test to activate fuel pump and pressurize fuel system. Note fuel pressure. Fuel pressure should be within specs. See FUEL PRESSURE SPECIFICATIONS table. If no fuel pressure exists, fuel pump relay and control circuit may be defective. See «FUEL PUMP RELAY»(ref-24887-S15446479962001010500000) under FUEL SYSTEM. If fuel pressure is correct, go to step 14).
- If fuel pressure is less than specified, go to step 7). If fuel pressure exceeds specification, check for kinked or restricted fuel return line from fuel filter to fuel pump module. Fuel filter is mounted on the frame, above rear of fuel tank, near fuel pump module on top of fuel tank. If fuel return line is not kinked or restricted, replace fuel pressure regulator. Fuel pressure regulator is mounted inside fuel tank, on fuel pump module. See procedures in «REMOVE/INSTALL/OVERHAUL - 2.5L»(ref-24888) article. Go to step 14).
- If fuel pressure is less than specified, release fuel pressure. Install Adapter (6539) and fuel pressure gauge between fuel filter outlet line and chassis fuel supply line. Fuel filter is mounted on the frame, above rear of fuel tank, near fuel pump module on top of fuel tank. Turn ignition on. Using scan tool, actuate ASD fuel system test. Note fuel pressure.
- If fuel pressure is now within specification, check for kinked or restricted chassis fuel supply line, and then go to step 14). If fuel pressure is still less than specified, go to next step.
- Release fuel pressure. Remove fuel pressure gauge and adapter from between fuel filter outlet line and chassis fuel supply line. Reconnect chassis fuel supply line to fuel filter. Install adapter and fuel pressure gauge between fuel pump module and fuel supply line to fuel filter.
- Turn ignition on. Using scan tool, actuate ASD fuel system test. Note fuel pressure. If fuel pressure is within specification, replace fuel filter along with fuel lines. Fuel lines are permanently attached to fuel filter. Go to step 14). If fuel pressure is still less than specified, go to next step.
- Release fuel pressure. Check for restriction in fuel supply line between fuel pump module and fuel filter. If restriction exists, replace fuel filter along with fuel lines, as fuel lines are permanently attached to fuel filter. Go to step 14).
- If no restriction exists, check for restricted fuel pump inlet strainer. Fuel pump inlet strainer located inside fuel tank, on bottom of fuel pump module. see scheme 3 Turn ignition on.
- Using scan tool, actuate ASD fuel system test to activate fuel pump and pressurize fuel system. Note fuel pressure. Fuel pressure should be within specs. See FUEL PRESSURE SPECIFICATIONS table. If no fuel pressure exists, fuel pump relay and control circuit may be defective. See «FUEL PUMP RELAY»(ref-24887-S15446479962001010500000) under FUEL SYSTEM. If fuel pressure is correct, go to step 14).
- If fuel pressure is less than specified, go to step 7). If fuel pressure exceeds specification, check for kinked or restricted fuel return line from fuel filter to fuel pump module. Fuel filter is mounted on the frame, above rear of fuel tank, near fuel pump module on top of fuel tank. If fuel return line is not kinked or restricted, replace fuel pressure regulator. Fuel pressure regulator is mounted inside fuel tank, on fuel pump module. See procedures in «REMOVE/INSTALL/OVERHAUL - 2.5L»(ref-24888) article for fuel pump module removal procedure.
- If fuel pump inlet strainer is restricted, replace fuel pump inlet strainer, and go to step 14). If fuel pump inlet strainer is not restricted, fuel pressure regulator or fuel pump are defective. Fuel pressure regulator and fuel pump are mounted inside fuel tank, on the fuel pump module. See the Fig. see scheme 4. Turn ignition on.
- Using scan tool, actuate ASD fuel system test to activate fuel pump and pressurize fuel system. Note fuel pressure. Fuel pressure should be within specs. See FUEL PRESSURE SPECIFICATIONS table. If no fuel pressure exists, fuel pump relay and control circuit may be defective. See «FUEL PUMP RELAY»(ref-24887-S15446479962001010500000) under FUEL SYSTEM. If fuel pressure is correct, go to step 14).
- If fuel pressure is less than specified, go to step 7). If fuel pressure exceeds specification, check for kinked or restricted fuel return line from fuel filter to fuel pump module. Fuel filter is mounted on the frame, above rear of fuel tank, near fuel pump module on top of fuel tank. If fuel return line is not kinked or restricted, replace fuel pressure regulator. Fuel pressure regulator is mounted inside fuel tank, on fuel pump module. See procedures in «REMOVE/INSTALL/OVERHAUL - 2.5L»(ref-24888) article. Go to step 14). CAUTION: After installing chassis fuel supply line on fuel line at front of fuel rail, ensure chassis fuel supply line is secured in place by pulling on chassis fuel supply line. If chassis fuel supply line is fully seated and secured in place, tabs on side of connector will be visible in each opening on side of the connector.
- Release fuel pressure. Remove test equipment. Before reinstalling chassis fuel supply line on fuel line at front of fuel rail, ensure fuel line and fittings are clean. Apply engine oil to fitting before installing fuel lines. Install chassis fuel supply line until click sound is heard. Pull on chassis fuel supply line to ensure fuel line is secured in place. Ensure tabs are fully seated and visible in openings on the side of the connector.
| Application | Psi (kg/cm 2 ) |
|---|---|
| Cirrus & Stratus | (1) 47-51 (3.3-3.6) |
| (1) Manufacturer lists fuel pressure with engine off, ignition on and using scan tool to activate fuel pump. | |
| (1) | Manufacturer lists fuel pressure with engine off, ignition on and using scan tool to activate fuel pump. |
FUEL PRESSURE SPECIFICATIONS
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 - 2.5L article. For additional information on diagnosis for fuel pump relay and control circuit, see NO START (NS) TEST in the TESTS W/CODES - 2.5L 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 the TESTS W/CODES - 2.5L article.
IDLE SPEED & IGNITION TIMING
Ensure idle speed and ignition timing are set to specification. For adjustment procedures, see appropriate ADJUSTMENTS - 2.5L article.
SUMMARY
If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to the TESTS W/CODES - 2.5L article. If no diagnostic trouble codes are found in self-diagnostics, proceed to the TESTS W/O CODES - 2.5L article for diagnosis by symptom (i.e., ROUGH IDLE, NO-START, etc.) or intermittent diagnostic procedures.