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 | 185 (13.0) |
| Minimum Compression Pressure | 139 (9.8) |
| Maximum Variation Between Cylinders | 14 (.9) |
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.
Scheme 115
Scheme 116
- Disconnect negative battery cable. Release fuel pressure. See «FUEL PRESSURE RELEASE»(ref-24878-S33269055812001010500000) under FUEL SYSTEM. CAUTION: Cover fuel plate with shop towel when removing, as some fuel pressure may exist in fuel rail.
- Remove bolts and fuel plate from end of fuel rail. Fuel plate is located on driver's side of front (radiator side) fuel rail. (Scheme 115) Fuel plate is near the air intake hose.
- Install Hose Adapter (MD998742), Adapter Hose (MD998709) and fuel pressure gauge on end of fuel rail. (Scheme 115) Connect scan tool to Data Link Connector (DLC), located below driver's side of instrument panel. (Scheme 116)
- 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 specification. See FUEL PRESSURE SPECIFICATIONS table. If no fuel pressure exists, fuel pump relay and control circuit may be defective. See FUEL PUMP RELAY under FUEL SYSTEM. If fuel pressure is correct, go to step 9). FUEL PRESSURE SPECIFICATIONS Application psi (kg/cm 2 ) Avenger & Sebring (1) 47-50 (3.3-3.5) (1) Manufacturer lists fuel pressure with engine off, ignition on and using scan tool to activate fuel pump.
- If fuel pressure exceeds specification, go to step 8). If fuel pressure is less than specified, check for clogged fuel filter. Fuel filter is located on frame rail, near fuel tank. Replace fuel filter if clogged, and recheck fuel pressure. If fuel pressure is now okay, go to step 9). If fuel pressure is still not within specification, go to next step.
- Check for fuel pressure in fuel return hose at fuel pressure regulator. Fuel pressure regulator is installed at "T" fitting at end of fuel filter, located on frame rail, near fuel tank.
- If fuel pressure exists in fuel return hose, fuel pressure regulator is leaking. If no fuel pressure exists in fuel return hose, low fuel pressure is caused by defective fuel pump. Fuel pump is located in fuel tank. Replace components as necessary. 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 specification. See FUEL PRESSURE SPECIFICATIONS table. If no fuel pressure exists, fuel pump relay and control circuit may be defective. See FUEL PUMP RELAY under FUEL SYSTEM. If fuel pressure is correct, go to step 9). FUEL PRESSURE SPECIFICATIONS Application psi (kg/cm 2 ) Avenger & Sebring (1) 47-50 (3.3-3.5) (1) Manufacturer lists fuel pressure with engine off, ignition on and using scan tool to activate fuel pump.
- If fuel pressure exceeds specification, go to step 8). If fuel pressure is less than specified, check for clogged fuel filter. Fuel filter is located on frame rail, near fuel tank. Replace fuel filter if clogged, and recheck fuel pressure. If fuel pressure is now okay, go to step 9). If fuel pressure is still not within specification, go to next step.
- Check for fuel pressure in fuel return hose at fuel pressure regulator. Fuel pressure regulator is installed at "T" fitting at end of fuel filter, located on frame rail, near fuel tank.
- If fuel pressure exists in fuel return hose, fuel pressure regulator is leaking. If no fuel pressure exists in fuel return hose, low fuel pressure is caused by defective fuel pump. Fuel pump is located in fuel tank. Replace components as necessary. See «REMOVE/INSTALL/OVERHAUL - 2.5L»(ref-24879) article.
- If fuel pressure exceeds specification, check for restricted fuel return hose or pipe. If fuel return hose or pipe are not restricted, check for a binding valve in the fuel pressure regulator. Fuel pressure regulator is installed at "T" fitting at end of fuel filter, located on the frame rail, near fuel tank. See «REMOVE/INSTALL/OVERHAUL - 2.5L»(ref-24879) article.
- If fuel pressure exceeds specification, check for restricted fuel return hose or pipe. If fuel return hose or pipe are not restricted, check for a binding valve in the fuel pressure regulator. Fuel pressure regulator is installed at "T" fitting at end of fuel filter, located on the frame rail, near fuel tank. See «REMOVE/INSTALL/OVERHAUL - 2.5L»(ref-24879) article. Once correct fuel pressure is obtained, go to next step.
- With scan tool actuated and fuel pressure obtained, turn ignition off and note fuel pressure. Fuel pressure should not decrease within 2 minutes.
- If fuel pressure decreases gradually after ignition turned off, check for leaky fuel injector/leaky valve in fuel pressure regulator. Fuel pressure regulator is installed at "T" fitting at end of fuel filter, located on frame rail, near fuel tank. Replace components as necessary. See the «REMOVE/INSTALL/OVERHAUL - 2.5L»(ref-24879) article. Go to step 12).
- If fuel pressure decreases immediately after ignition is turned off, check valve in fuel pump is held open. Replace fuel pump, located in fuel tank. See the «REMOVE/INSTALL/OVERHAUL - 2.5L»(ref-24879) article. Go to step 12).
- Ensure ignition is off. Remove scan tool. Release fuel pressure. Remove fuel pressure gauge. Reinstall fuel plate.
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 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.