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 | Specification | ||
|---|---|---|---|
| Compression Ratio | |||
| Ram Pickup (8.0L) | 8.4:1 | ||
| All Others | 9.1:1 | ||
| Normal Compression Pressure | (1) | ||
| Minimum Compression Pressure | |||
| Dakota | |||
| 2.5L | (1) | ||
| 3.9L, 5.2L & 5.9L | 100 psi (690 kPa) | ||
| Durango | 100 psi (690 kPa) | ||
| Ram Pickup | 100 psi (690 kPa) | ||
| Ram Van Ram Wagon | 100 psi (690 kPa) | ||
| Maximum Variation Between Cylinders | (1) | ||
| (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. |
FUEL PUMP RELAY
On all models, 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 TEST TC-101A in appropriate SELF-DIAGNOSTICS article.
3.9L, 5.2L & 5.9L
- Disconnect ignition coil secondary cable from center tower of distributor cap. Hold cable terminal about 1/2" (12 mm) from a good engine ground. Crank engine and observe cable terminal for a steady arc. If steady arcing occurs, go to step 3 . If steady arcing does not occur, go to next step.
- Check secondary coil cable resistance. Resistance should be 3000-12,000 ohms per foot. Also, inspect distributor cap and rotor for cracks or burn marks. If problem is found, repair as necessary. If problem is not found, go to next step.
- Connect ignition coil cable to distributor cap. Remove a cable from one spark plug. Using insulated pliers, hold cable terminal about 1/2" (12 mm) from engine cylinder head or block while cranking engine.
- If steady arcing occurs, it can be expected that ignition secondary system is operating correctly. If steady arcing occurs, but engine will not start, see appropriate NO START (NS) TEST in appropriate SELF-DIAGNOSTICS article.
8.0L
Information is not available from manufacturer.
IGNITION COIL
Note. For a complete test of ignition coil and its circuits, see TEST NTC-2A in appropriate SELF-DIAGNOSTICS article. Perform the following to test ignition coil only.
| Application | Primary | Secondary | ||
|---|---|---|---|---|
| Dakota & Durango | ||||
| Diamond (1) (2) | .97-1.18 | 11,300-15,300 | ||
| Toyodenso (1) | .95-1.20 | 11,300-13,300 | ||
| Ram Pickup | ||||
| Except 8.0L | ||||
| Diamond (1) (2) | .97-1.18 | 11,300-15,300 | ||
| Toyodenso (1) | .95-1.20 | 11,300-13,300 | ||
| 8.0L | .53-.65 | 10,900-14,700 | ||
| Ram Van & Ram Wagon | ||||
| Diamond (1) (2) | .97-1.18 | 11,300-15,300 | ||
| Toyodenso (1) | .95-1.20 | 11,300-13,300 | ||
| (1) This is the manufacturer of ignition coil. (2) Brass terminals. | ||||
| (1) | This is the manufacturer of ignition coil. |
| (2) | Brass terminals. |
IGNITION COIL RESISTANCE - Ohms @ 70-80°F (21-27°C)
Inspect ignition coil for arcing. Test coil according to coil tester manufacturer's instructions. Test coil primary and secondary resistance. See IGNITION COIL RESISTANCE - OHMS @ 70-80°F (21-27°C) table. Replace coil if resistance is not with specification of if there is evidence or arcing.
- To test secondary resistance of each individual paired coil, attach an ohmmeter across coil towers. This must be done across corresponding cylinders (3/2, 7/4, 1/6, 9/8 or 5/10). (Scheme 6) See «IGNITION COIL RESISTANCE - OHMS @ 70-80°F (21-27°C)»(ref-555-S19827420092003121800000) table.
- To test primary resistance of front coil pack, attach an ohmmeter between B+ coil terminal and corresponding coil terminal. (Scheme 7) Replace coil pack if resistance is not as specified.
Scheme 6
Scheme 7
IDLE SPEED & IGNITION TIMING
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 TEST TC-25A in appropriate SELF-DIAGNOSTICS 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 & RWD VANS - CNG & GASOLINE 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 - GASOLINE article for diagnosis by symptom (i.e., ROUGH IDLE, NO-START, etc.) or intermittent diagnostic procedures.