1998 Ford Mustang Fuel Pump Fuse: Location, Troubleshooting, and Essential Fixes

The 20-amp fuse located in the Power Distribution Box (PDB) under your Mustang's hood is the primary electrical protector for the 1998 Ford Mustang fuel pump. If your Mustang cranks but won't start, or suddenly dies while driving, a blown fuel pump fuse is one of the most critical and easiest things to check first.

Identifying and addressing issues with the fuel pump fuse is often the quickest path to resolving a no-start condition or stalling problem in your 1998 Mustang. This fuse acts as a safety device. It cuts power to the fuel pump circuit if an electrical overload occurs, preventing potential damage to wiring, the fuel pump relay, or the fuel pump itself. Knowing exactly where to look and how to properly diagnose this fuse is fundamental for any Mustang owner or mechanic.

Where to Find the 1998 Mustang Fuel Pump Fuse

  • The Location: Open the hood of your 1998 Ford Mustang. Locate the Power Distribution Box (PDB). This is a rectangular, usually black, plastic box situated near the back of the engine compartment, close to the firewall, on the passenger side. It contains multiple high-current fuses and relays vital for engine operation and accessories.
  • Identifying the Correct Fuse:
    • Look for the Diagram: The underside of the PDB cover has a detailed diagram and listing of every fuse and relay inside the box. Carefully lift off this cover.
    • Find Fuse #9: According to Ford's specifications and the diagram on the cover, the fuel pump fuse for the 1998 Mustang is Fuse #9. This fuse slot is typically labeled as "Fuel Pump," "FP," or "Fuel Pump/PCI".
    • The Fuse Itself: The fuel pump fuse is a standard 20-amp mini-blade fuse. You will recognize it by its blue plastic housing. Visually inspect it. If the thin metal strip inside the clear plastic body is broken or shows signs of melting/burning, the fuse is blown and must be replaced.
    • Visual Reference: Find the row closest to the front of the car (towards the headlights). Fuse #9 is usually in this front row, often the second or third fuse from the right-hand side (passenger side fender). Double-check this against the diagram on your specific PDB cover, as variations can occur, especially with different engine options (V6 or V8).

How to Check if the Fuel Pump Fuse is Blown

  1. Safety First: Ensure the ignition is OFF and the key is removed. Set the parking brake firmly. Allow the engine bay to cool if the engine was recently running.
  2. Access the Fuse: Open the hood and locate the Power Distribution Box (PDB) on the passenger side near the firewall. Carefully pry off the plastic cover. It usually clips on at each corner. Set the cover aside safely.
  3. Locate Fuse #9: Refer to the diagram on the underside of the PDB cover to visually identify Fuse #9. Remember, it should be a blue 20-amp mini-blade fuse.
  4. Visual Inspection: Carefully examine Fuse #9 through its clear plastic top. Look closely at the thin metal strip connecting the two metal blades.
    • Intact Fuse: The metal strip will be continuous and unbroken. It should look identical to a known good fuse of the same amperage (blue, 20A).
    • Blown Fuse: The metal strip will be visibly severed, melted, or show signs of discoloration (often black or brown) within the plastic housing. This interruption breaks the circuit.
  5. Physical Test (Optional): Use a fuse puller tool (often included in the PDB lid or your car's toolbox) to gently extract Fuse #9 from its slot. With the fuse removed, visually inspect it again. You can also use a multimeter set to the continuity setting (which beeps when there's a connection). Touch one probe to each of the fuse's metal blades:
    • Beep/Sound: The fuse is good (has continuity).
    • No Beep/Silence: The fuse is blown (no continuity) and must be replaced. Only use an identical replacement: a 20-amp mini-blade fuse (blue).
  6. Examine the Fuse Slot: Before inserting a new fuse, briefly inspect the empty fuse slot in the PDB. Ensure the metal contacts inside the slot look clean and undamaged, with no signs of melting or corrosion. Corrosion can be gently cleaned with electrical contact cleaner and a small brush.

Replacing a Blown Fuel Pump Fuse

  1. Confirm the Blown Fuse: Ensure you've correctly identified the blown fuse via visual or continuity check.
  2. Obtain Correct Replacement: Use only a new 20-amp mini-blade fuse with a blue plastic housing. Never use a fuse with a higher amperage rating (e.g., 25A or 30A), as this removes the critical safety protection and risks causing a fire by allowing excessive current to flow in a damaged circuit. Using a lower amp fuse is also incorrect; it will blow prematurely under normal operation.
  3. Insert New Fuse: Firmly press the new 20-amp fuse into the empty Fuse #9 slot until it seats completely. You should feel it click into place.
  4. Test Operation: Turn the ignition key to the "ON" position (do not start the engine yet). You should hear the fuel pump prime for approximately 2-3 seconds – it sounds like a distinct humming or buzzing noise coming from the rear of the car (fuel tank area). This is the prime cycle pressurizing the fuel system. If you hear this, the fuse and initial circuit are working. Attempt to start the engine.
  5. Cover Replacement: Once confirmed the fuse is seated and you've tested, securely snap the Power Distribution Box cover back into place.

What to Do If the New Fuse Blows Immediately

A common and critical situation arises: you replace the blown fuel pump fuse, turn the key to "ON," and the new fuse blows instantly, or blows as soon as you try to start the engine. This is a clear warning sign. It means there is a significant electrical short circuit somewhere in the fuel pump circuit. Continuing to replace the fuse repeatedly without addressing the underlying cause is extremely dangerous. Stop immediately.

A short circuit causing repeated fuse blowouts can result from:

  • Damaged Wiring: Wires pinched, frayed, rubbed through insulation (commonly near sharp edges, clamps, or where wiring passes through the body near the fuel tank). Rodent damage is a frequent culprit.
  • Faulty Fuel Pump: An internal short circuit within the fuel pump motor itself.
  • Damaged Fuel Pump Sender Assembly: Issues with the wiring connections or terminals on the pump hanger assembly mounted in the fuel tank.
  • Faulty Fuel Pump Relay: A relay that has failed internally in a shorted state (less common than fuse or wiring, but possible). The relay is also located in the PDB – check the diagram on the cover for its location (e.g., Relay #201). Swapping it with an identical relay (like the horn relay) can be a basic test, but a direct short will usually still blow the fuse even if the relay is good.
  • Aftermarket Accessory Conflicts: Improperly installed aftermarket stereo amplifiers, security systems, or other devices tapping into the fuel pump circuit can cause overloads.
  • Corrosion: Severe corrosion in wiring harness connectors related to the fuel pump circuit.

Essential Safety Precautions

  • Fire Hazard: Gasoline is highly flammable and explosive vapors are present. Never work on the fuel pump electrical circuit with the engine running or immediately after shutting it off. Allow time for heat to dissipate. Always have a suitable fire extinguisher (Class ABC or BC) nearby when performing any electrical work near the fuel system. Keep sparks, flames, and ignition sources far away.
  • Electrical Shock: While the voltages in the fuse box are relatively low (12V DC), it's still good practice to disconnect the negative (-) battery cable before handling fuses or relays if you suspect a serious short circuit or need to do extensive probing. This prevents sparks that could ignite fumes and eliminates accidental shorts while working.
  • Use Correct Amperage: As emphasized before, only use a 20-amp mini-blade fuse. Substituting a higher amperage fuse creates a severe fire risk. Using a lower amperage fuse will cause unnecessary failure under normal operating loads.
  • Seek Professional Help: If replacing the fuse doesn't solve the problem, or if the new fuse blows immediately, stop troubleshooting and seek assistance from a qualified automotive technician. Diagnosing short circuits requires specialized tools (like wiring diagrams and multimeters) and experience to avoid damage or injury, especially when dealing with the fuel tank wiring. Do not attempt to drop the fuel tank yourself unless you have the proper knowledge, tools, and safety equipment.

Beyond the Fuse: Related Troubleshooting

While the fuse is the most common failure point causing a sudden loss of fuel pump operation, it's not the only one. If your fuel pump fuse is intact, but the pump isn't running, consider these components next:

  1. Fuel Pump Relay: Located in the same Power Distribution Box (PDB) under the hood. It controls the high-current flow to the fuel pump based on signals from the Powertrain Control Module (PCM). A failed relay is a frequent cause of no-fuel conditions. Symptoms are identical to a blown fuse – no pump prime sound, engine cranks but won't start. Diagnosis involves swapping with an identical relay known to be good (check the PDB diagram for which relay is the fuel pump relay – often R201, and find a non-essential identical relay like the horn relay to swap for testing). Relays can also be bench-tested with a multimeter or power supply.
  2. Inertia Fuel Shutoff (IFS) Switch: A safety device designed to cut fuel pump power in the event of a collision impact. Located in either the passenger footwell kick panel or the trunk near the spare tire (exact location varies slightly by model year). If the switch is tripped, it disables the fuel pump. If your Mustang won't start after hitting a bump or pothole hard, this switch might have triggered. Resetting it is simple (press a prominent reset button on the switch), but you should also investigate why it tripped if there wasn't a major impact. These switches can also fail internally.
  3. Fuel Pump Wiring: Beyond the fuse box, the wiring runs from the engine bay to the fuel tank at the rear of the car. Check for damage along the entire route – under carpets, through bulkheads, and near heat sources. Look for corroded, loose, or broken connections, especially at the fuel pump inertia switch, fuel pump relay socket, and the connector at the fuel tank sender assembly. Bad grounds can also prevent the pump from running.
  4. Fuel Pump Driver Module (FPDM) - Note: The 1998 Mustang does not have an external FPDM. This component, which controls pump speed, was introduced in later years. On a 1998 Mustang, the fuel pump is controlled directly by the relay, based on commands from the PCM. Don't waste time looking for a non-existent FPDM.
  5. Fuel Pump Sender Assembly: This unit sits inside the fuel tank. It houses the fuel pump motor, the fuel level sending unit (float), and the main electrical connector. The pump motor itself can wear out or fail due to age, running the tank frequently on low fuel (overheating the pump), or contamination. The wiring harness connector on top of the assembly can become corroded. The fuel pump strainer (sock) can clog, though this usually causes poor performance rather than a complete no-pump situation.
  6. Powertrain Control Module (PCM): The vehicle's main computer controls the fuel pump relay. If the PCM does not receive the correct signals (like from the ignition switch or anti-theft system) or fails internally, it might not command the relay to turn on. This is less common than fuse, relay, or pump failure, but becomes more likely if other unrelated systems controlled by the PCM are malfunctioning.

Diagnosing a Non-Operational Fuel Pump (Fuse Intact)

If you hear the fuel pump run briefly when you turn the key to "ON," but the engine doesn't start, your issue may be elsewhere – bad fuel pressure (clogged filter, failing regulator, weak pump even if running), ignition problems, or lack of engine compression.

If you do not hear the fuel pump prime at all when the ignition is turned "ON," and you've confirmed the fuse is intact:

  1. Check the Fuel Pump Relay: Swap it as described above. Tap the relay – sometimes internal contacts stick. Check for power and control signals at the relay socket using a multimeter (requires wiring diagram).
  2. Reset the Inertia Switch: Locate the IFS switch (check trunk or passenger footwell) and firmly press the reset button.
  3. Test for Power at the Fuel Tank: This is a critical diagnostic step but requires accessing the fuel pump electrical connector. It's usually located near the top of the fuel tank, accessible by removing the trunk trim or rear seat cushion, depending on the body style (Coupe vs. Convertible). With the key turned to "ON," use a multimeter or a test light to check for battery voltage (approx. 12V) at the appropriate pins of the connector for those 2-3 seconds during the prime cycle. If you have power there, the problem is the fuel pump/sender assembly itself. If you do not have power there, the problem is upstream (wiring, relay, inertia switch, or PCM). This test involves working near the fuel tank – exercise extreme caution regarding sparks and fumes. Disconnecting the battery negative terminal is strongly recommended before probing this connector.

Conclusion: Your First Step When the Fuel Pump Stops

The 20-amp fuse dedicated to the fuel pump circuit within the under-hood Power Distribution Box (PDB) is the absolute first component you should inspect if your 1998 Ford Mustang cranks but refuses to start, or unexpectedly dies while running. Knowing its precise location (Fuse #9, blue 20A mini-blade fuse), how to visually and electrically test it, and understanding the necessity of replacing it only with the correct 20-amp fuse are critical pieces of knowledge for Mustang ownership.

While checking this fuse is simple, never underestimate the significance of a blown fuse. A replacement fuse solving the problem offers a quick fix. However, if that new fuse blows immediately upon restoring power, this demands immediate professional attention due to a dangerous short circuit lurking somewhere in the wiring or within the fuel pump assembly itself. Your safety and the integrity of your Mustang depend on correctly diagnosing and resolving fuel system electrical problems. The fuel pump fuse is the starting gate for this vital process.

Back to blog