1991 Ford Ranger Fuel Pump Relay Location: Find It Fast & Fix Your Fuel Problem

For owners of the 1991 Ford Ranger experiencing fuel delivery issues, the fuel pump relay is almost certainly located in the underhood power distribution box**, commonly found on the driver's side fender well near the battery.** Identifying and checking this crucial relay is often the first step in diagnosing a no-start or sputtering engine caused by fuel pump failure.

The Heart of Power Delivery: Why the Relay Matters

Before diving into the exact spot, understand the relay's job. Your fuel pump draws significant electrical current. Running this high power directly through the ignition switch and fuel pump switch (like an inertia switch) would quickly damage them. The fuel pump relay acts as a heavy-duty electrical switch, controlled by a low-current signal. When the ignition switch is turned to the "Run" or "Start" position (and crucially, after the Engine Control Module - ECM/PCM - receives a signal from the Crankshaft Position Sensor), it energizes the relay's coil. This pulls internal contacts closed, allowing battery current to flow directly to the fuel pump through thicker wiring. If the relay fails, this critical power path is cut, starving the fuel pump and preventing the engine from running.

Pinpointing the 1991 Ranger Fuel Pump Relay Location

Ford typically placed the relays and fuses responsible for engine and accessory functions in the engine compartment for the first-generation Ranger. For the 1991 model year, here’s the definitive location:

  1. Open the Hood: Ensure the vehicle is parked safely on level ground with the parking brake engaged. Pop the hood release inside the cab and secure the hood safely with the prop rod.
  2. Locate the Power Distribution Box (Fuse/Relay Box): Stand facing the engine bay from the front of the truck. Look towards the driver's side (left side in North American models). You will see a rectangular or square-ish black plastic box mounted on the inner fender well.
  3. Position Relative to Battery: This box is almost always positioned very close to the battery and often directly behind it or just slightly towards the front of the vehicle relative to the battery. It might be partially obscured by the battery or its hold-down bracket depending on battery size and placement.
  4. Identify the Box: The box will have a lid that can be removed. The lid usually features a molded diagram indicating the position and function of the fuses and relays inside. Look for text like "Power Distribution Box" or simply "Relays/Fuses."
  5. Opening the Box: Release the latches or clips holding the lid in place (often plastic tabs you squeeze together or pull upwards). Carefully lift the lid off. Place it aside safely.
  6. ️ Find the Fuel Pump Relay: Inside the box, you’ll see several cube-shaped or mini-cube-shaped relays (about 1 inch square or slightly larger). Locate the relay designated for the fuel pump.
    • Use the Diagram: This is the most reliable method. Examine the underside of the lid you removed. There will be a molded plastic map showing the position of each relay slot and its corresponding fuse. Find the slot labeled "Fuel Pump" or "FP."
    • Relay Slot Position: While Ford standardized layouts somewhat, variations can exist between production runs, different plants, or specific cab/chassis configurations. Generally, however, in the 1989-1992 Ranger power distribution box layout, the fuel pump relay is frequently found in the front row, often the position closest to the front of the truck (i.e., farthest from the firewall). Consult the diagram!
    • Relay Appearance: The fuel pump relay will look identical to other standard relays in the box (like the EEC Power relay, Horn relay, etc.). It usually has a gray or black plastic housing. Do not rely solely on color; rely on the lid diagram or physical position corresponding to the diagram. The diagram always trumps assumptions.
  7. Confirmation Check: Once you identify the relay based on the diagram's labeling in its specific slot position, you've found the fuel pump relay.

Why Location Matters: Symptoms & Testing

Knowing where it is empowers you to check it when troubleshooting:

  • Common Failure Symptoms: Intermittent no-start (engine cranks but won't fire), sudden engine stall while driving (especially on bumps), no fuel pump priming sound when you first turn the key to "Run," sputtering under load. Crucially, these symptoms can also point directly to the pump itself, the inertia switch, wiring faults, or the ECM. A failed relay is just one possible cause, but often the simplest and cheapest fix if diagnosed correctly.
  • Simple Relay Swap Test: The easiest way to test a suspected relay failure is by swapping it with a known good, identical relay from another slot (like the horn relay, which often uses the same type). To do this safely:
    1. Turn the ignition OFF.
    2. Identify the fuel pump relay (FP) using the lid diagram.
    3. Identify the horn relay (often nearby) using the diagram. Confirm they are the same physical type/part number.
    4. Carefully pull each relay straight up and out of its socket.
    5. Install the horn relay into the fuel pump relay socket.
    6. Turn the key to "Run" (do not start). Listen carefully near the fuel tank or have a helper listen. You should hear the fuel pump energize for 1-2 seconds (the priming sound). If you now hear the sound (which was previously absent), the original fuel pump relay is almost certainly faulty.
    7. Important: Immediately turn the key off. Reinstall the original horn relay back into its socket. Drive the vehicle only after installing a new fuel pump relay, as the horn circuit is now compromised.
  • Multimeter Testing (More Advanced): Using a digital multimeter, you can test the relay:
    1. Check Control Side (Coil): Set the multimeter to Ohms (Ω). Measure resistance between terminals 85 and 86 on the relay (terminal numbers are usually tiny markings on the bottom). A reading between 50-120 Ohms is typical. Infinite resistance indicates an open coil (bad relay). Zero resistance indicates a shorted coil (bad relay).
    2. Check Load Side (Contacts): Set the multimeter to Continuity (beep mode). With the relay removed, check between terminals 30 and 87a - there should usually be continuity (closed contact). Now check between terminals 30 and 87 - there should be no continuity. Apply 12V power to terminals 85 (+) and 86 (-). You should hear/feel an audible click. Now re-test continuity: 30 to 87a should become open, and 30 to 87 should now have continuity. If the relay doesn't click or the contacts don't switch states correctly, it's faulty. (Note: Some relays omit 87a; refer to specific terminal layout for Ford relay).
  • Power Probe Testing (Even Easier in Context): The fastest test is often done in the vehicle. Carefully remove the suspected fuel pump relay. Turn the ignition key to "Run." Using a power probe or multimeter set to DC Volts:
    1. Probe terminal 30 in the relay socket (refer to diagram or relay base numbering). Should read battery voltage (~12V) at all times.
    2. Probe terminal 86. Should read ground at all times (use continuity to chassis ground to confirm).
    3. Probe terminal 85. This is the control signal. When the key is turned to "Run," it should receive battery voltage for 1-2 seconds.
    4. Probe terminal 87 (the output to the pump). With the key cycled "Run," it should receive battery voltage for 1-2 seconds if the control circuit (85) and ground (86) are working correctly and fed by the ECM. If terminals 30, 85, and 86 all have correct signals but terminal 87 has no output during the key-on prime cycle, the relay is bad.
  • Listen! Always listen carefully for the pump's brief whine when turning the key to "Run" as a preliminary diagnostic step before even opening the hood.

Beyond the Relay: Related Systems to Consider

Knowing the relay location doesn't isolate the fault entirely. Diagnosing involves considering interconnected components:

  1. The Inertia Fuel Shutoff (Safety) Switch: This is a critical safety switch designed to cut power to the fuel pump in the event of a collision. Located in various spots depending on cab type (regular cab often passenger footwell kick panel near center hump, extended cab often on back wall behind driver seat), it can be tripped by a significant jolt (sometimes even a pothole) or become faulty. It must be manually reset by pressing a red button on its top. ALWAYS check this switch before diving into relay or pump replacement. Reset it if found popped up. No reset? Test power in/out using a multimeter similar to relay testing methods when keyed "Run".
  2. Fuel Pump Itself: Located inside the fuel tank. Requires draining the tank or running it extremely low before replacement. Diagnosis involves confirming power at the pump electrical connector (usually accessible near the tank under the truck) when the relay should be active, or checking fuel pressure at the fuel rail Schrader valve with a gauge. A silent pump despite confirmed power and ground means a dead pump.
  3. Fuel Filter: A severely clogged filter mimics fuel pump failure symptoms (loss of power, stalling). It's a critical maintenance item and easier/cheaper to replace than a pump or relay. The location varies (inline near tank, frame rail, engine bay).
  4. Wiring Harness: Damage, corrosion, or breaks in the wiring connecting the relay to the inertia switch, to the fuel pump, or providing power/ground/signal to the relay itself will cause failure. Inspect visually, check continuity/resistance and voltage drop tests at key points during cranking or priming.
  5. Engine Control Module (ECM/PCM): This computer controls the ground signal to the fuel pump relay coil (via terminal 85). If the ECM isn't getting signals it needs (like from the Crankshaft Position Sensor - CKP) or has failed internally, it won't trigger the relay. Advanced diagnostics needed. A bad CKP sensor is a very common cause of no-start conditions that mimic fuel pump failure (cranks but no start, no pump prime).
  6. Ignition Switch: Faults internal to the ignition switch can prevent power from reaching the ECM or the critical "start" and "run" circuits that initiate the fuel pump relay activation sequence. Requires switch testing.

Replacing a Faulty 1991 Ford Ranger Fuel Pump Relay

If testing confirms the relay is bad, replacement is straightforward:

  1. Obtain the Correct Part:
    • Use the number printed on the side of the old relay.
    • Go to a dealership parts counter and ask for the fuel pump relay for a 1991 Ford Ranger.
    • Order online using your VIN or make/model/year details. Ensure the part number matches Ford specifications (common numbers include F1DF-14B192-AA, F1SF-14B192-AA, equivalents from Bosch, Duralast, Standard Motor Works, etc.).
    • Visit any major auto parts store (NAPA, AutoZone, O'Reilly, Advance Auto Parts).
  2. Turn Off the Ignition: Ensure the key is OFF.
  3. Locate the Relay (as above).
  4. Remove the Old Relay: Firmly grasp the faulty relay and pull it straight up and out of its socket. Don't twist or pry; it should release with moderate force.
  5. Install the New Relay: Align the pins on the bottom of the new relay with the slots in the socket. Press straight down firmly until it seats completely.
  6. Test: Turn the ignition key to "Run" without starting the engine. Listen for the characteristic 1-2 second fuel pump priming whine. If you hear it, the new relay is working correctly at this stage.
  7. Reassemble: Put the lid back securely onto the Power Distribution Box, ensuring all clips latch properly.
  8. Attempt Start: If problem symptoms were isolated to the relay, the engine should now start and run normally.

Critical Safety Precautions

Working with electrical and fuel systems demands caution:

  • Disconnect the Battery: Before performing any electrical work beyond simple relay swapping/testing (especially pump replacement), disconnect the NEGATIVE (-) battery terminal to prevent shorts, sparks, or accidental engagement.
  • Relieve Fuel Pressure: Even with the battery disconnected, fuel pressure remains trapped in the fuel rail and lines downstream of the pump. Before disconnecting any fuel lines (e.g., at the pump connector or filter), relieve fuel pressure at the Schrader valve on the fuel rail using a dedicated pressure release tool or carefully wrapping rags around a screwdriver pressed onto the valve core (shield eyes/follow safety protocols).
  • Fire Risk: Gasoline vapors are extremely flammable. Work in a well-ventilated area. Keep sparks, flames, and cigarettes far away. Have a fire extinguisher rated for fuel/chemical fires readily accessible. Never work under the fuel tank with a test light or perform actions that could cause sparks near fuel components.
  • Ground Yourself: Prevent static discharge when working near the fuel pump by touching a clean, unpainted metal part of the vehicle chassis before handling the pump or related electrical connectors.
  • Support Vehicle Securely: If lifting the truck or crawling under it, always use proper jack stands on solid, level ground. Never rely solely on a hydraulic jack. Use wheel chocks.
  • Correct Replacement Parts: Using the incorrect relay type or rating can lead to electrical overload or fire hazard. Always match the OEM specification.

Maintenance and Troubleshooting Tips

  • Keep Contacts Clean: Relay sockets can develop corrosion or dirt over time. If a relay is suspect, carefully remove it and inspect the socket terminals. Use electrical contact cleaner and a soft brush to clean if necessary. Apply a tiny amount of dielectric grease to the relay pins before reinstalling to prevent future corrosion.
  • Carry a Spare: Fuel pump relays are relatively inexpensive and small. Consider carrying a spare in your glove box. Knowing its location empowers you to swap it quickly if it fails unexpectedly away from home.
  • Document Repairs: Note the date and mileage of relay (or pump/filter) replacements. Helps track maintenance and future diagnostics.
  • Systematic Diagnosis: Fuel delivery problems are frustrating. Always start with the simplest, cheapest, and easiest-to-check items: Check/Reset Inertia Switch > Listen for pump prime > Check Fuses > Swap/Test Relay > Test Fuel Pressure > Check for power at pump. Jumping straight to replacing the fuel pump is often costly and unnecessary if the real culprit is a $15 relay, blown fuse, or tripped inertia switch.

Conclusion: Knowledge is Power (Delivery)

For the 1991 Ford Ranger driver confronting a cranking engine that refuses to start, or unexpected stalling, the fuel pump relay nestled in the underhood power distribution box near the battery is a prime suspect. Locating this unassuming yet critical component is the gateway to an accurate diagnosis. While simple relay testing or swapping can often confirm failure and lead to a quick, inexpensive fix, always remember that these symptoms point to a system issue. Utilize the knowledge of the relay's location alongside a methodical approach – checking the inertia switch, confirming fuse integrity, inspecting wiring, and finally verifying actual pump operation or pressure – to accurately and efficiently resolve your Ranger's fuel delivery woes. Knowing precisely where to find the 1991 Ford Ranger fuel pump relay saves time, frustration, and potentially a significant repair bill. Keep that fuse box lid diagram handy – it's your roadmap to electrical troubleshooting under the hood.

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