Engine Controls - Basic Testing - 5.2l Dodge Pickup R3500

INTRODUCTION

The following diagnostic steps will help prevent overlooking a simple problem. This is also where 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 the conditions the problem reportedly occurred.

Before entering self-diagnostics, perform a careful and complete visual inspection. Most engine control problems result from mechanical breakdowns, poor electrical connections or damaged/misrouted vacuum hoses. Before condemning the computerized system, perform each test listed in this article.

Note. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure.

VISUAL INSPECTION

Visually inspect all electrical wiring, looking for chafed, stretched, cut or pinched wiring. Ensure electrical connectors fit tightly and are not corroded. Ensure vacuum hoses are properly routed and are not pinched or cut. Inspect air induction system for possible vacuum leaks.

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.

COMPRESSION SPECIFICATIONS

FUEL PRESSURE RELEASE

Vehicles With Fuel Rail Test Port

1. Loosen fuel tank filler cap. Ensure ignition is off. Remove protective cap from fuel rail test port.
2. Place one end of Fuel Pressure Release Hose (C-4799-1) into an approved fuel container. Attach remaining end of hose to fuel rail test port. Use care, as fuel system may be under pressure. Fuel pressure will be released from fuel system. Remove hose, reinstall protective cap, and fuel tank filler cap.
3. Wait 5 seconds. Use care when disconnecting fuel lines, as some fuel pressure may still exist in fuel lines.

Note. One or more DTCs may set when fuel pump relay is removed. Clear DTCs from PCM after fuel pressure release procedure. To clear DTCs from PCM, see CLEARING DTCS under SELF-DIAGNOSTIC SYSTEM in TESTS W/CODES - 5.2L article.

Vehicles Without Fuel Rail Test Port

1. 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.
2. 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.
3. 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 TESTS W/CODES - 5.2L article.

FUEL PRESSURE TEST

Note. For additional information on fuel pressure and fuel pump testing procedures, see appropriate NO TROUBLE CODE (NTC) TEST and NO START (NS) TEST in TESTS W/CODES - 5.2L article.

1. Disconnect negative battery cable. Release fuel pressure. See FUEL PRESSURE RELEASE under FUEL SYSTEM. Install fuel pressure gauge with hose on fuel pressure test port.
2. 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 under FUEL SYSTEM.
3. 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, at fuel pump module. See appropriate REMOVE/INSTALL/OVERHAUL - 5.2L article.

1. Disconnect negative battery cable. Release fuel pressure. See FUEL PRESSURE RELEASE under FUEL SYSTEM. Fuel pressure gauge is installed between fuel supply line and fuel line fitting on fuel rail.
2. To disconnect fuel supply line from fuel rail, ensure area around fuel supply line and fuel rail are clean. Note direction of latch clip installation. Latch clip is located on top of fuel supply line at fuel rail. (Scheme 2) Using 2 screwdrivers, pry latch clip upward, and remove from fuel rail.
3. Pull fuel supply line from fuel rail. Install Adapter (6923) into fuel rail. Ensure adapter is fully seated in fuel rail. Install latch clip into fuel rail, with latch clip fingers pointing downward. If latch clip will not fully seat so latch clip fingers extend downward below fitting on fuel rail, adapter may not be fully seated in fuel rail.
4. Connect fuel supply line to adapter. Ensure fuel supply line fully seats in adapter. Remove protective cap from test port, and install Fuel Pressure Gauge/Hose (5069) at test port.
5. 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 under FUEL SYSTEM.
6. 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, at fuel pump module. See appropriate REMOVE/INSTALL/OVERHAUL - 5.2L article.
7. Release fuel pressure. See FUEL PRESSURE RELEASE under FUEL SYSTEM. Remove latch clip. Remove test equipment. Before reinstalling fuel supply line, ensure fuel supply line fitting and fitting on fuel rail are clean.
8. Lubricate fuel supply line fitting and fitting on fuel rail with engine oil. Install fuel supply line on fuel rail.
9. Install latch clip into fuel rail, with latch clip fingers pointing downward. Ensure latch clip is fully seated. Latch clip fingers should extend downward below fitting on fuel rail when fully seated.
10. Pull on fuel supply line to ensure fuel supply line is fully locked on fuel rail. Reinstall negative battery cable. Start engine and check for fuel leaks.

Scheme 2

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, fuel pump will operate for approximately one second unless engine is running, or starter is engaged and engine is cranking. If engine cranking signal is not received, PCM will de-energize fuel pump relay.

Fuel pump relay receives battery voltage from fuse No. 9, located in junction block (fuse box). Junction block is located just inboard of left end of instrument panel.

Fuel pump relay is located in Power Distribution Center. Relays are identified on label under PDC cover. PDC is located near battery in left front corner of engine compartment.

If fuel pump relay or control circuit becomes defective, a Diagnostic Trouble Code (DTC) may be stored in the PCM. See DTC TEST in TESTS W/CODES - 5.2L article. For additional information on diagnosis for fuel pump relay and control circuit, see TEST TC-101A in TESTS W/CODES - 5.2L article.

IGNITION CHECKS

Note. For ignition system spark testing and component testing, see TEST NTC-2A in TESTS W/CODES - 5.2L article.

NO-START TESTING PROCEDURES

For additional information on no-start testing procedures, see TEST NS-1A in TESTS W/CODES - 5.2L article.

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 TESTS W/CODES - 5.2L 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 ADJUSTMENTS - 5.2L article.

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to TESTS W/CODES - 5.2L article. If no diagnostic trouble codes are found in self-diagnostics, proceed to TESTS W/O CODES - 5.2L article for diagnosis by symptom (i.e., ROUGH IDLE, NO-START, etc.) or intermittent diagnostic procedures.