INTRODUCTION
Note. For diagnostic procedures on systems used in common with gasoline powered vehicles, proceed to BASIC TESTING - 5.2L GASOLINE article in the ENGINE PERFORMANCE section.
The following diagnostic steps can help prevent overlooking a simple problem. Also use this article to begin diagnosis for a no-start condition. The first step in diagnosing any driveability problem is verifying the customer's complaint with a test drive under conditions in which the problem reportedly occurs.
Before entering self-diagnostics, perform a careful and complete visual inspection. Most driveability and no-start problems are not related to computerized engine control systems, but are simple mechanical, electrical, fuel or vacuum related faults. Most engine control problems are the result of mechanical breakdowns, poor electrical connections, or damaged or misrouted vacuum hoses. Before condemning the computerized engine control system, perform each test listed in this article.
Note. All voltage tests should be performed using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance unless stated otherwise in testing procedures.
VISUAL INSPECTION
Perform a visual inspection of all electrical wiring. Look for chafed, stretched, cut or pinched wiring. Inspect electrical connectors and connections for tight fit and corrosion. Repair as necessary. Inspect all vacuum hoses for improper routing, cuts and pinches. Repair as necessary. Inspect air induction system for possible vacuum leaks.
FUEL PRESSURE
Note. Before testing is attempted, ensure fuel tanks are 1/4 full (minimum). Low fuel level (1/8-1/4) may cause poor performance and/or no-start condition.
Begin basic diagnosis of fuel system by determining fuel pressure.
Fuel System Pressure Test
- On Ram Van/Wagon, remove engine cover. Remove air cleaner assembly. On all models, connect pressure gauge (0-300 psi) to service port on fuel injector rail. Start engine and monitor fuel pressure.
- Minimum operating pressure is 90 psi, and maximum operating pressure is 140 psi. Operating pressures can be affected by: Outside ambient temperature. Low-pressure fuel shutoff solenoid condition. Fuel injector(s) condition. High-pressure fuel shutoff solenoid and solenoid relay condition. Engine load requirements.
- If fuel pressure is more than 140 psi (fuel tanks 1/8 full-minimum), replace fuel pressure regulator. See «REMOVE/INSTALL/OVERHAUL - 5.2L CNG»(/dodge/ram-van-b1500/b-pre-1995-1995/remont/removal-installation/#engine-controls-removeinstalloverhaul-52l-cng) article in the ENGINE PERFORMANCE section.
- If fuel pressure is less than 90 psi, ensure all fuel cylinders have sufficient fuel level (1/8 or more). Ensure manual shutoff valve and all fuel control valves are fully open. Inspect fuel tubes for kinks and restrictions.
- Inspect and test low-pressure fuel shutoff solenoid, high-pressure fuel shutoff solenoid and fuel injectors. See «SYSTEM/COMPONENT TESTS - 5.2L CNG»(/dodge/ram-van-b1500/b-pre-1995-1995/remont/testing-diagnostics/#engine-controls-systemcomponent-tests-52l-cng) article in the ENGINE PERFORMANCE section. Inspect fuel system for leaks. See «LEAK TESTING»(/dodge/ram-van-b1500/b-pre-1995-1995/remont/testing-diagnostics/#engine-controls-basic-testing-52l-cng) . Remove fuel pressure gauge. On Ram Van/Wagon, install air cleaner assembly and engine cover.
System Leak Testing
If a fuel system leak is suspected, inspect system tubing with a commercially available liquid leak detector. Ensure fuel system is fully pressurized. Apply a generous amount of leak detector fluid to suspected leak area. Monitor area for 3-5 minutes. A steady source of bubbles should appear at leak area. Repair as needed. See SYSTEM/COMPONENT TESTS - 5.2L CNG article in the ENGINE PERFORMANCE section. If fuel cylinder leak is suspected, cylinder must be replaced.
NO-START TEST (FUEL)
Note. Perform TESTING SPARK AT COIL under IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES - GASOLINE article before proceeding with test.
Note. Before testing is attempted, ensure fuel tanks are 1/4 full (minimum). Low fuel level (1/8-1/4) may cause poor performance and/or no-start condition. For testing and repair procedures for no-start fault, see appropriate test in TESTS W/CODES - 5.2L CNG article in the ENGINE PERFORMANCE section.
AUTO SHUTDOWN (ASD) & FUEL SOLENOID SHUTOFF RELAY
Note. If auto shutdown or fuel solenoid shutoff relay is suspected in causing no-start fault, see appropriate test in TESTS W/CODES - 5.2L CNG article in the ENGINE PERFORMANCE section.
SUMMARY
If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, go to TESTS W/CODES - 5.2L CNG article in the ENGINE PERFORMANCE section. If no Diagnostic Trouble Codes (DTCs) are found in self-diagnostics, go to TESTS W/O CODES - CNG article in the ENGINE PERFORMANCE section for diagnosis by symptom (i.e., ROUGH IDLE, NO-START, etc.) or intermittent diagnostic procedures.