Compression
Ensure battery is fully charged. Warm engine to normal operating temperature. Disconnect wire at ignition coil to prevent engine from starting. Check engine compression with all spark plugs removed and throttle wide open.
Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer manual for specific instructions.
| Application | Psi (kPa) | ||
|---|---|---|---|
| Normal Compression Pressure | (1) | ||
| Minimum Compression Pressure | |||
| Dakota | |||
| 2.5L | 120-150 (827-1034) | ||
| 4.7L | (1) | ||
| 3.9L & 5.9L | 100 (690) | ||
| Durango | 100 (690) | ||
| Ram Pickup | |||
| 3.9L, 5.2L & 5.9L | 100 (690) | ||
| 5.9L Diesel & 8.0L | (1) | ||
| Ram Van Ram Wagon | 100 (690) | ||
| Maximum Variation Between Cylinders | |||
| Except Dakota 2.5L | (1) | ||
| Dakota 2.5L | 30 (206) | ||
| (1) Information is not available from manufacturer. | |||
| (1) | Information is not available from manufacturer. |
COMPRESSION SPECIFICATIONS
FUEL PRESSURE RELEASE
| WARNING | Fuel system is under high pressure. ALWAYS release fuel pressure before attempting to open system for testing or component replacement. DO NOT allow fuel to flow onto engine or electrical parts while testing fuel system components. |
All Models
- Remove gas cap. Using a non-metallic tool, open flapper valve in filler neck to relieve pressure. Remove fuel pump relay from Power Distribution Center (PDC). Relays are identified on label under PDC cover. Start and run engine until it stalls. Attempt to start engine. Continue restarting engine until it will no longer run. Turn ignition off. CAUTION: DO NOT supply power to fuel injector for more than 4 seconds, or fuel injector may be damaged.
- Disconnect any fuel injector connector. Connect a jumper wire between either fuel injector terminal and positive battery terminal. Connect another jumper wire to other fuel injector terminal. Momentarily touch other end of jumper wire to negative battery terminal.
- Place a shop towel under fuel line quick-connector at fuel rail. Use care when disconnecting fuel lines, as some fuel pressure may still exist in fuel lines. Disconnect fuel line quick-connector. Reinstall fuel pump relay in PDC. Clear DTCs from PCM. To clear DTCs from PCM, see CLEARING DTCS under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article.
- Disconnect negative battery cable. Release fuel pressure. See «FUEL PRESSURE RELEASE»(ref-9164-S33206637422000100900000) . Install fuel pressure gauge with hose on fuel pressure test port.
- Start engine and allow to idle. Fuel pressure should be 44-54 psi (3.1-3.8 kg/cm 2 ). If no fuel pressure exists and engine will not start, fuel pump relay and control circuit may be defective. See «FUEL PUMP RELAY»(ref-9164-S40731193612000100900000) .
- If fuel pressure exceeds specification, fuel pump is okay, but fuel pressure regulator is defective. Replace fuel pressure regulator. Fuel pressure regulator is incorporated with the fuel filter. Fuel filter/fuel pressure regulator is located on top of fuel tank, in fuel pump module. See «REMOVAL, OVERHAUL & INSTALLATION - TRUCKS & RWD VANS - GASOLINE»(ref-9080) article.
Ram Pickup
If fuel pump relay or control circuit becomes defective, a Diagnostic Trouble Code (DTC) may be stored in the PCM. For additional information on diagnosis for fuel pump relay and control circuit, see DTC P1282: FUEL PUMP RELAY CONTROL CIRCUIT under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - RAM PICKUP - GASOLINE article.
Ram Van & Ram Wagon
If fuel pump relay or control circuit becomes defective, a Diagnostic Trouble Code (DTC) may be stored in the PCM. For additional information on diagnosis for fuel pump relay and control circuit, see DTC P1282: FUEL PUMP RELAY CONTROL CIRCUIT under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - RAM VAN & RAM WAGON article.
IGNITION CHECKS
Note. For ignition system spark testing and component testing, see SELF-DIAGNOSTICS - RAM PICKUP - GASOLINE or SELF-DIAGNOSTICS - RAM VAN & RAM WAGON article.
For no-start testing procedures, see TEST NS-SEL: NO START TEST SELECTION under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - RAM PICKUP - GASOLINE article.
For no-start testing procedures, see TEST NS-SEL: NO START TEST SELECTION under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - RAM VAN & RAM WAGON article.
Idle speed and mixture are controlled by Powertrain Control Module (PCM). No adjustment is required. PCM controls Idle Air Control (IAC) motor for proper idle speed. See DTC P0505: IDLE AIR CONTROL MOTOR CIRCUITS and/or TEST NTC-13: CHECKING IDLE AIR CONTROL MOTOR under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - RAM PICKUP - GASOLINE article.
Idle speed and mixture are controlled by Powertrain Control Module (PCM). No adjustment is required. PCM controls Idle Air Control (IAC) motor for proper idle speed. See DTC P0505: IDLE AIR CONTROL MOTOR CIRCUITS and/or TEST NTC-9: CHECKING MINIMUM IDLE AIR FLOW under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - RAM VAN & RAM WAGON article.
Ignition timing is controlled by PCM and is nonadjustable. If vehicle is equipped with a distributor, DO NOT attempt to adjust timing by rotating distributor. If distributor is rotated, fuel system synchronization will be changed. If distributor is rotated or removed, check fuel system synchronization. See FUEL SYSTEM SYNCHRONIZATION under FUEL SYSTEM in ON-VEHICLE ADJUSTMENTS - TRUCKS article.
SUMMARY
If no faults were found while performing basic diagnostic procedures, proceed to appropriate SELF-DIAGNOSTICS article. If no diagnostic trouble codes are found in self-diagnostics, proceed to TROUBLE SHOOTING - NO CODES - EXCEPT DIESEL article for diagnosis by symptom (i.e., ROUGH IDLE, NO-START, etc.) or intermittent diagnostic procedures.