Engine Controls - Basic Engine Testing - 5.0L: Other Ford Pickup F350

Compression

Check engine mechanical condition using a compression gauge, vacuum gauge or engine analyzer. If using engine analyzer, see engine analyzer manual for specific instructions. Compression pressures are considered within specifications if lowest reading cylinder is within 75 percent of highest reading cylinder.

Exhaust System Backpressure

Using a vacuum or pressure gauge, check exhaust system. Remove Heated Oxygen Sensor (HO2S) or air injection check valve (if equipped). Connect a 0-5 psi pressure gauge, and run engine at 2500 RPM. If exhaust system backpressure is greater than 2 psi, exhaust system or catalytic converter is plugged.

If using a vacuum gauge, connect vacuum gauge hose to intake manifold vacuum port, and start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge reading slowly drops after stabilizing, check exhaust system for restrictions.

PRELIMINARY CHECKS

Ensure following systems and components are in good condition and operating properly before diagnosing problems in fuel injection system.

1. Check battery and charging system condition.
2. Check all wiring and vacuum connections.
3. Check air cleaner and ducting.
4. Check state of tune.
5. Check fuel delivery system.
6. Check cooling system.
7. Check inertia fuel shutoff switch.
8. Check for hydrostatic lock (liquid in cylinder).
9. Check fuel tank contents and fuel gauge accuracy.
10. Check for dirt, water or other contamination in fuel.
11. Check fuel lines and fittings for leaks.
12. Check fuel delivery system for proper pressure and volume.
13. Check for inoperative fuel injectors.
14. Check for improperly installed electronic equipment such as anti-theft system, CB radio, cellular telephone or stereo.

Engine Does Not Crank

Check for enabled anti-theft system. Check starting and charging system for correct operation. Check for hydrostatic lock (liquid in cylinder). Repair as necessary.

Engine Cranks But Will Not Start

1. Check fuel tank contents and fuel gauge accuracy. Check for dirt, water or contamination in fuel.
2. Check fuel lines and fittings for leaks. If no leaks are found, check fuel delivery system for proper pressure and volumes. Reset Inertia Fuel Shutoff (IFS) switch (if necessary).
3. Check for damaged or contaminated fuel injector wiring harness and connector. Ensure fuel injectors pulse when engine is cranked.
4. Check ignition system for strong secondary current at spark plugs. If no spark exists or if spark is weak, repair ignition system. See the «TESTS W/CODES - 5.0L»(ref-23596) article.

FUEL SYSTEM PRESSURE RELEASE

1. Remove fuel tank cap. Connect Fuel Pressure Gauge (T80L-9974-B) to pressure relief valve (Schrader valve), located on fuel injection manifold rail. Place fuel pressure gauge in a suitable container. Using gauge, release pressure from system.
2. If fuel pressure gauge is not available, disconnect Inertia Fuel Shutoff (IFS) switch. See «INERTIA FUEL SHUTOFF (IFS) SWITCH LOCATION»(ref-23708-S06557768782002010900000) table. Remove fuel cap to release fuel tank pressure. Crank engine for 15 seconds to release system pressure.

INERTIA FUEL SHUTOFF (IFS) SWITCH LOCATION

FUEL PRESSURE

Note. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article.

1. Release fuel pressure. Install fuel pressure gauge. Turn ignition on and read fuel pressure. Start engine and read fuel pressure. Compare fuel pressure reading on fuel pressure gauge with specifications. For fuel pressure specifications, see «FUEL PRESSURE SPECIFICATIONS»(ref-123322) article.
2. If fuel pressure is not within specifications, check fuel pressure regulator. With engine running, connect hand vacuum pump and apply vacuum to regulator.
3. Ensure fuel pressure changes as vacuum at regulator is increased and decreased. If no pressure change occurs, replace regulator and recheck system. For additional testing information, see FUEL SYSTEM in the «TESTS W/CODES - 5.0L»(ref-23596) article.

Scheme 392

FUEL PUMP PERFORMANCE

Fuel Injector Check

1. Connect tachometer to engine. Run engine at idle. Disconnect and reconnect injectors individually. When disconnected, each injector should cause a momentary drop in engine speed of at least 100 RPM. Engine RPM drop should only be momentary as Powertrain Control Unit (PCM) will attempt to re-establish correct idle RPM.
2. Replace any injectors that do not cause sufficient drop in engine speed. When test is complete, check idle speed. Refer to emission control specifications on decal in engine compartment. See «IDLE SPEED & IGNITION TIMING»(ref-23708-S10498834622001010300000) .

Fuel Injector Resistance

Disconnect injector harness connectors. Using digital ohmmeter, measure resistance between injector terminals. See INDIVIDUAL INJECTOR RESISTANCE table. Replace any injector not within specification.

Note. For additional testing and information, see FUEL SYSTEM in the TESTS W/CODES - 5.0L article.

INDIVIDUAL INJECTOR RESISTANCE (1)

INERTIA SWITCH

1. In event of a collision, electrical contacts in inertia switch open, automatically shutting off fuel pump. Fuel pump shuts off even if engine does not stop running. Engine will stops due to lack of fuel.
2. Engine cannot be restarted until inertia switch is manually reset. To reset inertia switch, depress button on switch. See «INERTIA FUEL SHUTOFF (IFS) SWITCH LOCATION»(ref-23708-S34643849082002010900000) table.

INERTIA FUEL SHUTOFF (IFS) SWITCH LOCATION

DEFINITION

No-start is defined as engine cranks okay, but does not start. Engine may fire a few times.

Before diagnosing problems in ignition system, ensure following systems and components are in good condition and operating properly.

1. Battery.
2. State of engine tune.
3. Fuel delivery and injection system.
4. All wiring and vacuum connections.
5. Air cleaner and ducts.
6. Cooling system.

Spark Check

1. Perform self diagnostic QUICK TEST to check for ignition-related fault codes, and repair as necessary. See QUICK TEST in the «TESTS W/CODES - 5.0L»(ref-23596) article. If no fault codes are retrieved, check ignition system wiring harness connectors for corrosion and tight fit. See the «WIRING DIAGRAMS - 5.0L»(ref-23666) article. Clean or repair connectors as necessary.
2. If wiring and connectors are okay, use Neon Bulb Spark Tester (D89P-6666-A) to check for spark at each spark plug wire while cranking engine. If spark is strong and consistent at each spark plug (one spark per crankshaft revolution), ignition system is okay. If spark is not present, see test procedures under IGNITION SYSTEMS in the «TESTS W/CODES - 5.0L»(ref-23596) article.

IGNITION COIL RESISTANCE

IGNITION COIL RESISTANCE

IDLE SPEED & IGNITION TIMING

Ensure idle speed and ignition timing are set to specification. See appropriate table. For adjustment procedures, see the ADJUSTMENTS - 5.0L article.

Note. Always refer to Emission Control Label in engine compartment before attempting service. If manual and label differ, always use emission label specifications.

IDLE RPM SPECIFICATION

BASE IGNITION TIMING

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to TESTS W/CODES - 5.0L article. If no trouble codes found in self-diagnostics, proceed to TESTS W/O CODES - 5.0L article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.