1999 Ford Expedition Fuel Pump Fuse: Location, Testing, and Troubleshooting Guide

If your 1999 Ford Expedition cranks but won't start, and you suspect a fuel delivery problem, checking the fuel pump fuse is the absolute first and easiest step. Located in the main under-hood Power Distribution Box (PDB), specifically fuse position #17, this 20 Amp mini fuse is critical for supplying power to the fuel pump relay and ultimately the fuel pump itself. A blown fuse here is a common culprit causing a sudden no-start condition or engine stalling. This comprehensive guide details everything you need to know to locate, inspect, test, and replace this vital fuse, helping you diagnose this issue quickly and safely.

The Vital Role of the Fuel Pump Fuse

Automotive fuses are safety devices designed to protect electrical circuits from overloads caused by excessive current flow, such as from a short circuit or component failure. The fuel pump circuit draws significant power. The fuse designated for this circuit acts as the first line of defense. If an electrical fault occurs downstream – perhaps a short in the fuel pump wiring, a failing pump motor drawing too much current, or a problem with the relay – the fuse will blow (the thin metal strip inside melts). This breaks the circuit, cutting power to the fuel pump relay and the fuel pump itself, preventing potential fire hazards or damage to more expensive components like the relay or the Powertrain Control Module (PCM). Simply put, no power through the fuel pump fuse equals no fuel pump operation and no engine start if the truck relies solely on the in-tank pump for fuel delivery to the engine.

Precise Location in the Power Distribution Box (PDB)

For the 1999 Ford Expedition, the fuel pump fuse resides solely in the primary fuse and relay box located under the hood. This is officially called the Battery Junction Box (BJB) or Power Distribution Box (PDB). It is typically a large, rectangular black plastic box, usually found near the battery or against one of the fender walls.

  1. Open the Hood: Secure the hood prop rod safely.
  2. Locate the PDB: Identify the main black plastic fuse/relay box. Consult your owner's manual if unsure; it will have a diagram showing its location. On most 1999 Expeditions, it's on the driver's side near the firewall or battery.
  3. Remove the PDB Cover: The cover is secured with clips or simple screws. Release these and lift the cover off. Attached to the underside of this cover you will find the most crucial resource: a detailed fuse and relay layout diagram. Do not proceed without this diagram! Labels on the box itself can fade or be inaccurate.
  4. Identify Fuse #17: Locate the section for the mini blade fuses. Using the diagram on the underside of the cover, find the position labeled "#17".
  5. Confirm Fuse Rating: According to official Ford service manuals (such as those published by Helm Inc.), wiring diagrams, and common repair practices, the fuel pump fuse for the 1999 Expedition is a 20 Amp mini blade fuse. This specific amperage is critical. Using a lower-rated fuse risks it blowing prematurely under normal operation. Using a higher-rated fuse removes the critical protection it provides and risks damage to wiring.
  6. Optional Relay Identification (Adjacent): While not the fuse, the fuel pump relay is also located within this same PDB. The relay diagram on the cover will show its position (often labeled "Fuel Pump," "FP," "EEC," or "PCM Relay" – consult the diagram). Knowing its location is helpful for advanced troubleshooting steps covered later. Fuse #17 powers the control side of this relay.

Essential Tools for Fuse Testing and Replacement

Handling fuses requires minimal tools, but having the right ones is important:

  1. Fuse Puller: Most PDB covers include a small plastic fuse puller tool clipped onto the cover. This is the safest and easiest way to remove fuses without damage.
  2. Needle-Nose Pliers (Alternative): If no puller is present, small needle-nose pliers can carefully grasp the fuse body. Crucially, never pull on the fuse blades themselves. Squeeze the pliers on the plastic body.
  3. Flashlight/Work Light: Good illumination is necessary to clearly see the fuse's internals through the plastic body and to navigate the PDB.
  4. Replacement Fuses: Always have spare fuses on hand. You need a 20 Amp mini blade fuse. Confirm it's the physical mini blade size (ATR style is incorrect). Ensure it's the same color as the original (yellow for 20 Amp). Good quality replacements (e.g., Bussmann, Littelfuse) are recommended.
  5. Multimeter (Recommended for Best Accuracy): While a visual inspection is common, a digital multimeter is the definitive tool for confirming a fuse is blown and for advanced electrical testing. Set it to continuity (usually a diode symbol or sound icon) or the lowest Ohms (Ω) setting.
  6. Safety Glasses: Protect your eyes when working under the hood.
  7. Gloves: Nitrile or mechanics gloves protect hands from minor abrasions and dirt.

Step-by-Step Guide to Removing and Inspecting Fuse #17

  1. Ensure Safety: Park the vehicle on a level surface, engage the parking brake firmly, and remove the ignition key.
  2. Locate & Open PDB: As described above, open the hood and locate the Power Distribution Box. Remove its cover and identify fuse #17 using the diagram.
  3. Remove the Fuse: Use the dedicated plastic fuse puller tool. Insert it over the top of the fuse and gently squeeze the puller legs to grip the fuse body, then pull straight up. If using pliers, grip the plastic body firmly but gently and pull straight up.
  4. Perform a Visual Inspection: Hold the fuse up to a bright light source. Look through the transparent plastic body at the thin metal strip connecting the two blade terminals. A good fuse will show a completely intact, unbroken metal strip from one blade to the other. A blown fuse will show a visible break (gap) in the metal strip, often accompanied by discoloration (black or metallic residue) or cloudiness inside the plastic. This indicates the fuse has failed.
  5. Perform a Multimeter Test (Highly Recommended):
    • Set the multimeter to the continuity test setting (audible beep symbol) or Ohms (Ω). If using Ohms, select the lowest range (like 200 Ohms).
    • Touch one multimeter probe to each of the fuse's metal blades.
    • Continuity Test: If the multimeter beeps continuously, the fuse is good. No beep means the fuse is open (blown).
    • Ohms Test: A reading very close to 0.0 Ohms indicates a good fuse. A reading of O.L. (Over Limit) or infinite resistance means the fuse is blown.
    • This test is definitive even if visual inspection is ambiguous.

What to Do If Fuse #17 is Blown

  1. Replace with the Correct Fuse: Insert a brand new 20 Amp mini blade fuse into position #17. Ensure it's fully seated in the socket.
  2. Critical Warning: Do not simply replace the fuse repeatedly. A blown fuse is a symptom of a problem elsewhere in the circuit. Repeatedly replacing blown fuses without finding the root cause is ineffective and potentially dangerous. The new fuse will blow again until the underlying fault is fixed.
  3. Check for Immediate Re-blowing: Turn the ignition key to the ON position (do not start the engine). Listen carefully: you should hear the fuel pump run for about 2-3 seconds to prime the system. If you hear it, turn the key to OFF. Now turn the key ON again; the pump should cycle again. If the new fuse blows immediately when turning the key ON, this confirms a severe short circuit exists downstream. Proceed with caution to advanced troubleshooting.

Troubleshooting Beyond a Blown Fuse

If replacing the fuse fixed the problem immediately and the truck starts normally, and only if it was a one-time isolated incident like a known power surge (very rare), you might be lucky. However, a fuse blowing without an obvious external cause always indicates an underlying electrical fault. Here's how to proceed:

  1. Confirm the Problem Persists: After replacing the fuse, does the truck start? If yes, carefully monitor for recurrence. If it blows again or the truck won't start/stalls again, move to advanced troubleshooting.
  2. Inspect the Fuel Pump Relay (Adjacent in PDB): Consult the diagram to locate the fuel pump relay. Swap this relay with another identical one in the PDB (common compatible relays might be for the horn, blower fan, or similar). Turn the key ON. If the fuel pump now runs (and the original problem - like horn not working - moves to the other circuit), the relay is faulty and needs replacement.
  3. Check for Wiring Damage: This requires more advanced skills. Inspect the wiring harness near the relay, along the frame rails, and especially where it passes through the floor near the rear of the truck to reach the fuel pump in the tank. Look for chafed wires, melted insulation, or damaged connectors. Pay close attention to the harness routing above the rear axle. Damage here is common due to vibration and debris. Use the wiring diagram for the 1999 Expedition fuel system for reference (available in factory service manuals or reputable online repair databases like ALLDATA or Mitchell1).
  4. Fuel Pump Resistance Test (Requires Access): This usually requires accessing the fuel pump connector near the tank or dropping the tank. Safety is paramount - fuel vapors are explosive. Disconnect the pump's electrical connector. Set your multimeter to Ohms (Ω). Measure the resistance between the pump's power and ground terminals (consult wiring diagrams for exact pinout). Compare this reading to the specification for the specific pump (typically 0.5 - 3.0 Ohms; exact specs vary). A reading significantly lower than spec (near 0 Ohms) indicates a shorted pump motor. A reading much higher than spec or O.L. indicates an open circuit within the pump motor. A pump drawing excessive current internally can blow the fuse even if its resistance seems normal during a static test.
  5. Circuit Voltage Testing: With the ignition ON (or during cranking), use a multimeter to check voltage:
    • At Fuse #17 Socket: Should have battery voltage (approx. 12V).
    • At the Fuel Pump Relay Socket: Test the control circuit voltage (when key ON, voltage should appear on the coil terminals briefly). Test the main power feed to the relay input terminal (should have constant battery voltage). Test the relay output terminal (power going to the pump) when the relay should be active (should get voltage when the pump should be running). Requires understanding relay operation.
    • At the Fuel Pump Connector (Backprobe Safely): With the key ON or while cranking (requires a helper), voltage should appear at the pump's power wire. Use caution to avoid shorts.
  6. Inertia Switch: While not powered by fuse #17 directly, the fuel pump circuit on the 1999 Expedition passes through an inertia safety switch, typically located on the firewall, passenger footwell, or rear cargo area wall. This switch shuts off the fuel pump during a significant impact. Check if this switch has been tripped (a button on top pops up). Reset it by firmly pressing the button down. Ensure its wiring is intact.
  7. Ground Point Inspection: Locate the ground connections for the fuel pump circuit. Common ground points might be near the battery, along the frame, or near the pump itself. Ensure connections are clean, tight, and free of corrosion. A poor ground can cause circuit malfunctions.

When Replacement Becomes Necessary

  • Fuse: Only replace the 20A mini fuse with an identical new fuse after diagnosing why it blew. Never substitute with a higher amperage fuse.
  • Relay: If confirmed faulty by swapping, replace it with the correct Ford part number or a direct high-quality automotive equivalent.
  • Fuel Pump: If testing confirms the pump is failed (open circuit, shorted, or mechanically seized/drawing excessive current), replacement is necessary. This is a significant job usually requiring dropping the fuel tank. Consider replacing the fuel filter and the pump's strainer sock while you have access. Use a reputable brand pump assembly (Airtex, Carter, Bosch, Delphi, or Motorcraft).
  • Wiring: Damaged wiring must be repaired properly. Cut out the damaged section and splice in a new section of the correct gauge wire using quality crimp connectors (preferably adhesive-lined heat shrink butt connectors) or soldering with heat shrink tubing insulation. Ensure repairs are protected from abrasion and moisture. If harness damage is extensive or near the PCM, professional help is strongly advised.

Safety Warnings - Critical Considerations

  1. Fire Hazard: Fuel and electrical sparks are a dangerous combination. Disconnect the battery negative terminal before beginning any work involving potential sparks near the fuel tank, pump, or lines (like wiring repairs or tank removal). Have a fire extinguisher rated for gasoline fires (Class B) nearby.
  2. Gasoline Handling: Gasoline is toxic and flammable. Avoid skin contact and breathing vapors. Work in a well-ventilated area, away from ignition sources. Plug open fuel lines immediately when disconnected. Relieve fuel system pressure using the Schrader valve on the fuel rail before opening fuel lines, if possible (requires a specific tool).
  3. Electrical Safety: Disconnect the battery negative terminal when performing any wiring repairs or testing that could cause a short. Use appropriate insulated tools.
  4. Vehicle Support: If lifting the vehicle or dropping the fuel tank, use proper jack stands rated for the vehicle's weight on a solid, level surface. Never work under a vehicle supported only by a jack.
  5. Know Your Limits: If you are uncomfortable with electrical diagnosis, working with fuel systems, or lifting the vehicle, seek professional help from a qualified mechanic. Dealing with the fuel system electrical circuits involves significant risks if done improperly. Incorrect diagnoses or repairs can be costly and potentially dangerous.

Conclusion: Start Simple with the Fuse

A sudden no-start condition in your 1999 Ford Expedition where the engine cranks but won't fire can be caused by numerous issues. However, checking the fuel pump fuse (#17, 20A mini fuse in the Power Distribution Box under the hood) is always the fastest and simplest initial diagnostic step. A visual or multimeter check takes only moments. While replacing a blown fuse might temporarily restore function, it is vital to understand that a blown fuse signals a deeper problem within the fuel pump circuit, such as a short in the wiring, a failing relay, or an internal fault in the fuel pump itself. Simply replacing the fuse without further diagnosis is ineffective and potentially hazardous due to fire risks. Follow the systematic location, testing, and troubleshooting steps outlined here to safely and effectively diagnose whether the fuse is the root cause or merely pointing you toward the true culprit in your fuel delivery system. Always prioritize safety when working with automotive electrical systems and fuel.

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