1999 Harley Davidson Road King Fuel Pump Relay Location (The Definitive Guide)

The fuel pump relay on your 1999 Harley Davidson Road King (FLHR/FLHRI) is located under the rider's seat, mounted directly to the frame crossmember just behind the battery box.

Finding this crucial electrical component is essential when troubleshooting fuel delivery issues. Knowing exactly where it is saves significant time and frustration. This guide provides a detailed, step-by-step description of its position and related information vital for any 1999 Road King owner or mechanic.

Understanding the Fuel Pump Relay's Role

Before locating it, understanding what the fuel pump relay does clarifies why its position matters. The fuel pump relay acts as an electronically controlled switch for the fuel pump circuit. Your ignition switch sends a low-power "turn on" signal to the relay when you first turn the key to ON (before starting) and while the engine is running. The relay receives this signal and responds by closing a high-power circuit connection, sending the full battery voltage needed to operate the electric fuel pump inside the tank. This allows a small switch (ignition) to control the large current demands of the pump safely. Without a functioning relay, the pump receives no power, meaning no fuel pressure, and the engine won't start or will stall shortly after starting.

Precise Location Description: Under the Seat

Removing the rider's seat provides the primary access point to most electrical components on this model Road King. Once the seat is off, direct your attention to the rear fender area just behind the battery box. The battery itself sits within a black plastic or metal housing towards the front under the seat.

  1. The Crossmember: Look for a horizontal metal bar (the frame crossmember) that runs side-to-side, spanning the space between the upper rear sections of the frame rails. This crossmember sits directly above the rear fender.
  2. Near the Battery Box: Position yourself so you can see the back side of the battery box. The crossmember is immediately behind the back edge of this battery box housing.
  3. Relay Orientation: Mounted vertically (pointing up and down) on the RIGHT SIDE (starboard side, as if sitting on the bike) of this frame crossmember, facing generally towards the front of the bike. It will be oriented so its connectors point downward or slightly downward and towards the rear fender.
  4. Identifying Features: The relay itself is a roughly rectangular black plastic module, approximately 1.5 inches long, 1 inch wide, and 1 inch tall. It has multiple electrical terminals/pins (usually 4 or 5) protruding from its bottom, plugged into a matching socket which is attached to a metal mounting bracket. This bracket is bolted directly to the frame crossmember. You will see wires leading into the socket block plugged into the bottom of the relay. On most 1999 Road Kings, it is often the only relay-type component mounted on the right side of that rear crossmember. Look for the primary power cable leading towards the main fuse block/harness and the pump power cable heading down towards the tank.

Accessing the Fuel Pump Relay: Step-by-Step

Locating it is step one; accessing it requires a few simple tools:

  • Phillips head screwdriver or appropriate size hex key/Allen wrench (depending on your specific seat mounting hardware).
  • Optional but helpful: Flashlight for better visibility.
  1. Safety First: Ensure the motorcycle is parked securely on a stable level surface. Engage the jiffy stand (kickstand). Turn the ignition key to OFF and remove the key. Allow a few minutes for hot components to cool if the engine was recently running.
  2. Seat Removal: The solo rider's seat on the 1999 Road King is typically held on by either two bolts accessible from the sides or a single bolt at the front center near the gas tank.
    • If your seat uses two side bolts: Locate the bolt heads (often Phillips head) protruding horizontally near the rear of the seat on each side. Unscrew these bolts completely. Lift the seat straight up and back to remove it.
    • If your seat uses a single front bolt: Locate a bolt head (sometimes requiring a hex key) on a bracket protruding from the seat pan near the front center where the seat meets the tank. Unscrew this bolt completely. Lift the rear of the seat slightly, then slide the entire seat directly rearward until its front mounting hooks disengage from the frame/tank bracket. Lift the seat off.
  3. Gain Clearance: With the seat removed, you now have a clear view of the top of the rear fender, the battery box, and the frame crossmember behind the battery box. The wiring harness and relays are exposed.
  4. Locate the Specific Relay: Position yourself on the left side (port side) of the motorcycle facing across towards the right side of the frame crossmember. As described above, identify the horizontal crossmember bar. Scan along the right side of this bar. Look for the distinctive black plastic relay module mounted vertically. It should be easily visible.

Recognizing the Fuel Pump Relay

It's crucial to correctly identify the fuel pump relay, especially as there might be other relays nearby for the starter, ignition, or accessories. Here are key identifiers:

  1. Physical Appearance: Standard automotive/cubical style mini ISO relay. Black plastic housing, typically with the Harley Davidson part number and other markings molded on one side (e.g., common replacements might be marked H-D 70492-96, 31950-96, 70496-96, or Bosch 0332201150 - but markings can fade or differ).
  2. Terminals: It will have either four or five terminals (blades) protruding from the bottom, plugged into a socket. A 4-pin relay is simpler; a 5-pin often has two different output terminal types.
  3. Wiring: Trace the thickest wire leading out of the relay socket – this is usually the power wire from the main fuse/feed coming into the relay. Another thick wire should lead away from the relay socket downwards towards the fuel tank area – this is the critical power wire heading to the fuel pump itself.
  4. Functionality Check (If Necessary): If you need to confirm it's the fuel pump relay specifically, listen carefully when you turn the ignition key to ON. You should hear a distinct "CLICK" sound coming from the relay under the seat. Simultaneously, you should hear the fuel pump prime ("whirring" sound for 1-2 seconds) coming from the gas tank area. Hearing the relay click and the pump prime when turning the key on strongly indicates the relay is functioning correctly.

Why Does This Specific Location Matter?

Harley-Davidson places components based on accessibility, wire routing efficiency, environmental protection, and proximity to related systems. Placing the fuel pump relay under the seat offers several advantages:

  1. Centralized Access: Under-seat placement gathers key electrical components (battery, fuses, starter relay, ECM sometimes) into one service area, simplifying diagnostics and maintenance. Mechanics can access multiple components by removing just the seat.
  2. Wire Routing Efficiency: Locating the relay near the battery minimizes the length of the heavy-gauge power cable needed to supply high current from the battery to the relay (via the main fuse). The power feed wire from the main fuse block (also likely nearby) can be short. The output wire running from the relay to the fuel pump travels down behind the engine and along the frame to the tank, a reasonably direct path.
  3. Moderate Protection: While not fully weatherproof, the location under the seat provides significant protection from direct road spray, rain (unless parked uncovered for extended periods), and minor debris compared to components mounted lower on the frame. This area also stays cooler than locations near the exhaust headers. Harley-Davidson designed the under-seat area on touring models like the Road King to offer adequate protection for these critical electrical items during normal operation.
  4. Heat Mitigation: While the area near the engine can get very hot, the frame crossmember location is positioned relatively high and rearward, away from the primary heat sources like exhaust pipes and engine heads, helping prolong the relay's lifespan compared to lower or forward mounting positions.
  5. Security: Being under a locked seat deters casual tampering or theft attempts on critical electrical components.

Symptoms Pointing to a Faulty Fuel Pump Relay

Understanding the location becomes urgent when symptoms arise. A failing fuel pump relay is a common cause of fuel-related no-start conditions on older Harleys like the 1999 Road King. Be alert for these telltale signs:

  1. "Silent" Key On: The most diagnostic symptom: You turn the ignition key to ON (without hitting the starter), but you hear no click from under the seat and no priming whine from the fuel pump inside the tank. Your bike's fuel system should prime briefly at key-on.
  2. Failure to Start: The engine cranks strongly (the starter spins the engine over) but refuses to fire up or run. This indicates spark might be present but no fuel is being delivered to the injectors.
  3. Sudden Engine Cut-Out: While riding, the engine abruptly shuts off as if the ignition was turned off. Often accompanied by loss of electrical power (gauges, lights).
  4. Intermittent Starting Issues: The bike starts normally sometimes, but then refuses to start at other times, often correlated with engine temperature (a failing relay can become intermittent as heat affects the internal connections). You might get lucky turning the key on and off multiple times until you finally hear the pump prime.
  5. Engine Runs, Then Dies Shortly After Starting: The bike starts and might run for a few seconds (fuel already in the rail) but then stalls as the pump isn't being powered continuously by the faulty relay.

Verifying the Problem: Testing the Relay

Before replacing parts, confirmation is wise. Relays are inexpensive, so replacement is often the simplest fix, but testing can be done:

  • Audible & Tactile Test (Key ON): As described earlier, listen carefully for the relay "click" under the seat and feel for a slight clicking vibration when touching its housing as someone turns the key to ON. No click strongly suggests failure. Hearing the pump prime confirms both relay and pump are working at that moment.
  • Swap Test (Simplest Method): Identify other relays in the same under-seat area (e.g., starter relay, which shares very similar electrical characteristics and might be identical). Swap the suspect fuel pump relay with a known good relay from another critical system like the starter circuit. Turn the key ON. If the fuel pump now primes (and you hear the audible click), your original fuel pump relay is faulty. Note: Make sure the relay you swap in has the same pin configuration (4 or 5 pin).
  • Basic Voltage Test (Requires Meter):
    1. Turn ignition OFF.
    2. Identify the relay's terminals. You may need a wiring diagram, but generally: Two terminals are for the control coil (one gets switched ignition power, one typically goes to ground). Two terminals are the high-current switch (one gets fused battery power, one feeds power to the pump).
    3. Set your multimeter to DC Volts (20V scale).
    4. Check for constant battery voltage: Find the terminal that has constant 12V+ relative to ground (bike frame), regardless of key position. This is the main power feed into the relay.
    5. Check for ignition-switched voltage: Find the coil terminal that gets +12V only when the ignition is ON. You'll need to probe while turning the key on.
    6. Check for coil ground: The opposite coil terminal should show continuity to ground (ohmmeter, key OFF) or near 0V when the ignition is ON relative to battery negative.
    7. Check output while activating: If you have a helper turn the key ON, the output terminal (going to the pump) should jump to nearly full battery voltage (12V+) relative to ground when the relay clicks.
  • Continuity Check (Relay Removed):
    1. Remove the relay from its socket.
    2. Identify the coil terminals (typically terminals 85 & 86). Use your multimeter on ohms (lowest scale). There should be measurable resistance (typically 50-150 ohms) between these two pins. Infinite resistance (open circuit) or zero resistance (short) indicates a bad coil.
    3. Identify the switch terminals (typically 30 & 87, and 87a if 5-pin). On a standard normally-open relay (like the fuel pump), terminals 30 and 87 should show infinite resistance (open) with no power applied. When you apply 12V DC power (use jumper wires or a 9V battery carefully) to terminals 85 (+) and 86 (-), you should hear a click and the meter should show near zero resistance (closed) between terminals 30 and 87. Removing power should cause it to "click" open again.

Replacing the 1999 Road King Fuel Pump Relay

Once you've confirmed the relay is faulty, replacement is straightforward:

  1. Obtain Correct Replacement: Get the right relay. Common Harley part numbers for this era include 70492-96, 31950-96, 70496-96, 70433-96. OEM Harley relays or high-quality Bosch/HELLA equivalents like Bosch 0332201150 are recommended. Verify pin configuration (4 or 5 pin) before purchase. Genuine Harley relays often have a metal bracket attached which is necessary for mounting. Generic relays may require reusing your existing bracket.
  2. Access: Remove the rider's seat as described earlier.
  3. Identify Old Relay: Locate the faulty relay on the right side of the frame crossmember behind the battery box.
  4. Disconnect: Firmly grasp the relay body (not the wires) and pull it straight out of its plastic socket block. Sometimes it takes a bit of force. If it feels stuck, wiggle slightly while pulling. DO NOT pull on the wires connected to the socket block underneath.
  5. Remove from Bracket (If Necessary): Most relays are snapped into a metal bracket bolted to the frame. Carefully pry or depress any small locking tabs holding the relay into the metal bracket and remove the old relay.
  6. Transfer Bracket (If Needed): If your new relay didn't come with a bracket, transfer the mounting bracket from the old relay to the new one. Ensure it clicks securely into place.
  7. Install New Relay: Align the pins on the bottom of the new relay with the holes in the socket block. Press down firmly and evenly until you hear it click fully home into the socket.
  8. Re-Mount Bracket (If Removed): If you needed to unbolt the entire metal bracket/socket assembly to access it better, bolt it securely back onto the frame crossmember.
  9. Function Test: DO NOT replace the seat yet. Turn the ignition key to ON. You should immediately hear a distinct "CLICK" from the new relay and a simultaneous 1-2 second fuel pump priming sound from the gas tank area. This confirms correct installation and function.
  10. Reassemble: If the test is successful, replace the rider's seat securely.

Related Components and Troubleshooting

Sometimes the problem isn't the relay itself. Consider and check these related areas:

  1. Fuel Pump Fuse: This is arguably the first thing to check if the pump isn't priming. This vital fuse protects the entire fuel pump circuit. On the 1999 Road King, you will typically find two primary fuse locations:
    • Main Fuse Block: Under the seat, near the battery. Look for a small black plastic box containing several blade-type fuses. The fuel pump fuse is usually clearly labeled "F/PMP" or "FUEL" and is commonly a 15-amp fuse (blue color). Visually inspect it to see if the metal strip inside is intact. Test it for continuity with your meter.
    • Circuit Breaker: Older Harleys sometimes used a self-resetting circuit breaker instead of a fuse for the pump. You might see it labeled "Fuel Pump" near the main fuse block. Press its button to see if it's tripped.
  2. Ignition Switch: Provides the signal power that activates the relay coil. A problem here means no signal reaches the relay to tell it to turn on the pump. Symptoms might be broader electrical issues, not just the pump.
  3. Wiring Harness & Connections: Damage or corrosion anywhere in the relay control circuit or power circuit can mimic a bad relay. Inspect connectors at the relay socket, battery terminals, fuse holders, and where the pump wire exits the main harness to go to the tank. Look for fraying, chafing, corrosion, or loose pins.
  4. Ground Points: Poor grounding, especially the ground for the relay coil, will prevent the relay from activating. Locate the main ground points under the seat and near the battery; ensure connections are clean, tight, and rust-free.
  5. Fuel Pump Itself: While the relay is a common failure point, the pump itself can also fail. If you hear the relay click strongly but hear no pump prime from the tank (and the fuse is good), the pump is suspect. Replacing it requires tank removal.
  6. ECM Issues: While less common than a relay or fuse failure, a problem with the Electronic Control Module (ECM) could theoretically prevent it from signaling the relay correctly. This is more complex to diagnose and requires specialized tools or dealer support.

Maintenance Tips to Prevent Relay Issues

Relays are wear items, especially on frequently ridden motorcycles exposed to vibration and temperature cycles. However, you can prolong their life:

  1. Keep Under-Seat Area Clean: Regularly remove the seat and blow out accumulated dust, grime, and leaf debris that can hold moisture and lead to corrosion on terminals over time. Wipe surfaces down. A clean environment prevents poor conductivity and overheating at connections.
  2. Inspect Connections: Periodically, especially at the start of the riding season or after long storage, inspect the relay socket terminals and the relay pins for any signs of burning, corrosion (green/white powder), or looseness. Spraying dielectric grease sparingly onto the relay pins before insertion can help prevent moisture ingress and corrosion formation on critical contacts.
  3. Address Electrical Gremlins Promptly: If you notice any flickering lights, intermittent gauge operation, or other electrical quirks, investigate promptly. These can indicate underlying issues (like poor grounding or a failing alternator/battery) that stress the electrical system and components like the fuel pump relay more than necessary.
  4. Carry a Spare Relay: Given their relatively low cost and critical importance, it's highly recommended for owners of bikes this age to carry a known-good spare relay. Taping it securely under the seat for roadside emergencies can save you from needing a tow. Knowing exactly where it is makes swapping it quick and easy.

Conclusion: Key Takeaway

The fuel pump relay is a critical but simple component on your 1999 Harley Davidson Road King. When seeking the 1999 Harley Davidson Road King Fuel Pump Relay Location, remember: it's mounted vertically on the frame crossmember under the rider's seat, positioned on the right-hand side just behind the battery box. Removing the seat provides direct access. Understanding this precise location, learning to recognize the relay, knowing how to test it, and performing basic preventive checks empowers you to quickly diagnose and resolve a common cause of fuel delivery failure on these iconic touring motorcycles, keeping you confidently on the road.

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