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Home >> Ford >> 2003 >> Excursion 5.4 L, 4WD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 3 (Engine Controls - System & Component Testing - 7.3L Diesel) >> Hard Start/No-Start Diagnostic Procedures >> Test 10: Glow Plug System Operation >> Recommended Procedure (Federal)
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Recommended Procedure (Federal)

WARNING: This page is about a different variant/trim than selected.

Insufficient glow plug "On" time will not allow enough heat to accumulate in combustion chamber resulting in a hard start condition. If glow plug system "On" time is insufficient, probable cause is a faulty wiring harness connector, bad ground connection or defective glow plug relay. If glow plug resistance to ground is high, probable cause is an open circuit in Under Valve Cover (UVC) wiring harness or an open glow plug.

    NOTE: The glow plug relay will not come on if EOT is above 131°F (55°C) for F250-550, and 86°F (30°C) for Econoline.
    Fig 1: Checking Power To Glow Plug Relay
    G99J02503Courtesy of FORD MOTOR CO.
    NOTE: Each valve cover gasket has 2 glow plug/fuel injector connectors that are part of the gasket. Each connector is responsible for 2 glow plugs/fuel injectors. If connector is faulty, replace valve cover gasket.
  1. Connect a DVOM between ground and Black/Orange wire at glow plug relay. If battery voltage is not present, locate and repair open in Black/Orange wire between glow plug relay and starter relay. If battery voltage is present, connect DVOM between ground and Brown wire at glow plug relay. See Fig 1. Turn ignition on and note how long glow plug relay stays energized, then de-energizes ("On" time). Relay will make a loud click noise when it energizes. Compare relay "On" time to specifications. See GLOW PLUG RELAY SPECIFICATIONS  table. If relay "On" time is not within specification, check wiring and connections. If wiring and connections are okay, replace relay. If "On" time is within specification, go to next step.
    GLOW PLUG RELAY SPECIFICATIONS (1)

    Engine Oil Temperature - °F (°C) "On" Time - Seconds
    Econoline
    32 (0) 120
    50 (10) 60
    68 (20) 30
    86 (30) 0
    Excursion & F250-550
    14 (-10) 120
    68 (20) 70
    122 (50) 40
    131 (55) 0
    (1) Specification listed is with vehicle at sea level and battery voltage at 12 volts. Specification is approximate.
    2. NOTE: All injector connectors must be disconnected at both valve cover gaskets, or resistance measurements will be incorrect.
  2. Turn ignition off. Disconnect all 4 glow plug/fuel injector connectors at valve cover gaskets. Install Glow Plug Injector Adapter (014-00935) to any injector connector at valve cover gasket. See Fig 2. Using DVOM, measure resistance between negative battery terminal and each glow plug test point at glow plug injector adapter. If all resistances are .1-2.0 ohms, go to next step. If any resistance is not .1-2.0 ohms, probable cause is an open in Under Valve Cover (UVC) wiring harness or an open glow plug. Repair as necessary.
  3. Using DVOM, measure resistance between Brown wire at glow plug relay and each glow plug test point at glow plug injector adapter. If all resistances are less than 1.0 ohm, no problem is indicated at this time. If any resistance is 1.0 ohm or more, locate and repair open circuit.
Fig 2: Checking Glow Plug Resistance
G99B02504Courtesy of FORD MOTOR CO.
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