1985 Camaro Fuel Pump Relay Location: Find It Fast & Fix Fuel Issues

The fuel pump relay for your 1985 Chevrolet Camaro is located inside the passenger compartment, specifically under the dashboard on the passenger side footwell area, mounted on or near the main fuse block assembly.

If you're experiencing fuel delivery problems like a no-start condition or the engine sputtering and dying, a faulty fuel pump relay is a prime suspect. Knowing exactly where to find this critical relay is the first step in diagnosing and resolving the issue. This guide provides detailed, step-by-step instructions to locate, identify, test, and replace the fuel pump relay in your third-generation F-Body.

Understanding the Fuel Pump Relay's Role

Before diving under the dash, it's helpful to understand what the relay does and why its location matters. The fuel pump relay acts as a heavy-duty switch controlled by a smaller electrical signal. Its primary job is to provide the high current necessary to power the electric fuel pump located inside the fuel tank. When you turn the ignition key to the "Run" position, the Powertrain Control Module (PCM) or a separate fuel pump control module (depending on the exact 1985 configuration) sends a signal to energize the relay. This closes the relay's internal contacts, allowing battery voltage to flow through the relay and directly to the fuel pump, priming the fuel system. When you start the engine, the pump continues to run as long as the engine is cranking or running. If the relay fails, it cuts power to the pump, preventing fuel delivery and causing the engine to stall or not start at all.

Detailed Location: Passenger Side Footwell

Finding the relay requires accessing the area beneath the dashboard on the passenger side:

  1. Prepare the Vehicle: Ensure the ignition is OFF. Park the Camaro on a level surface and engage the parking brake firmly. For safety and easier access, it's highly recommended to disconnect the negative (-) battery cable. Use the appropriate size wrench (usually 5/16" or 8mm) to loosen the clamp bolt on the negative terminal. Remove the cable and place it away from the battery post.
  2. Access the Passenger Footwell: Open the passenger door fully. You'll need to position yourself on the floor or crouch down outside the vehicle, looking up under the dashboard towards the firewall (the metal wall separating the engine compartment from the passenger compartment).
  3. Locate the Main Fuse Block: Directly above the passenger's feet, mounted vertically on the firewall or very close to it, you will find a rectangular black plastic housing. This is the main fuse block assembly. It contains numerous fuses protecting various circuits and several electrical relays.
  4. Identify the Relay: The fuel pump relay is one of several similar-looking relays plugged into sockets on this fuse block. Relays are typically cube-shaped components, larger than fuses, often black or gray in color. They plug into sockets with multiple electrical terminals. The exact position of the fuel pump relay socket can vary slightly depending on the specific model (e.g., Z28, Berlinetta, IROC-Z) and options, but it will be among the relays on this fuse block assembly.

Identifying the Correct Relay

Since multiple relays look identical, you need a reliable way to identify the fuel pump relay:

  1. Consult the Fuse Block Cover Diagram: The most accurate method is to check the diagram printed on the inside of the fuse block cover. Carefully remove the cover by pressing any retaining clips and pulling it straight off. Look for the legend or diagram. The fuel pump relay socket should be clearly labeled. Common labels include "FP," "FUEL PUMP," "F/PMP," or "ECM B" (as it was often tied to the Engine Control Module/PCM power circuit). Sometimes it might be labeled by its function number, like "Relay #10" (a common designation for the fuel pump relay in GM vehicles of this era). Match the label on the diagram to the physical socket on the fuse block.
  2. Relay Characteristics: If the diagram is missing or faded, you can look for identifying features:
    • Terminals: The fuel pump relay typically has four or five spade terminals on the bottom.
    • Socket: The socket it plugs into will have corresponding female terminals.
    • Position: While not foolproof, the fuel pump relay is often positioned near other critical relays like the main power relay (sometimes labeled "ECM" or "PCM") or the horn relay.
  3. Electrical Schematics: For absolute certainty, especially if modifications have been made, consulting a factory service manual wiring diagram for your specific 1985 Camaro is the definitive way to identify the correct relay and socket.

Symptoms of a Failing Fuel Pump Relay

Knowing the location is crucial when you experience these common signs of relay failure:

  • Engine Cranks But Won't Start: The most obvious symptom. The engine turns over normally when you turn the key, but it never fires up because no fuel is being delivered to the engine.
  • Engine Stalls Suddenly While Driving: The relay fails while the engine is running, cutting power to the fuel pump instantly, causing the engine to die as if the ignition was turned off.
  • Intermittent Starting Problems: The relay works sometimes and fails other times. You might experience a no-start condition that mysteriously resolves itself after waiting a while (as a failing relay contact might temporarily re-make connection when it cools down).
  • No Fuel Pump Prime Sound: When you turn the ignition key to the "Run" position (before cranking), you should hear a distinct whirring or humming sound from the rear of the car (near the fuel tank) for about 2 seconds. This is the fuel pump priming the system. If you hear no sound at all during this prime cycle, it strongly points to a lack of power reaching the pump, often due to a failed relay, fuse, or the pump itself.
  • Clicking Sound from Relay Area: Sometimes, a failing relay with sticking contacts might produce a rapid clicking sound from under the dash when the ignition is turned on, indicating it's trying but failing to engage properly.

How to Test the 1985 Camaro Fuel Pump Relay

Once you've located the suspected relay, testing it is straightforward. You have two main options:

  1. The Swap Test (Simplest Method):

    • Identify another relay on the fuse block that has the exact same physical shape, terminal configuration, and markings (often the horn relay or headlight relay).
    • Carefully pull the suspected fuel pump relay straight out of its socket. Note its orientation before removal.
    • Pull the known good relay (e.g., horn relay) from its socket.
    • Insert the known good relay into the fuel pump relay socket. Ensure it's fully seated and oriented correctly.
    • Turn the ignition key to the "Run" position (do not crank). Listen carefully near the rear of the car for the fuel pump priming sound (2-second whir/hum).
    • If the fuel pump now primes, the original relay in that socket is faulty.
    • If there's still no prime sound, the problem lies elsewhere (fuse, wiring, pump, PCM).
    • Remember to return the good relay to its original socket and replace the faulty fuel pump relay.

  2. Basic Bench Test with a Multimeter:

    • Remove the relay from its socket.
    • Identify the terminals on the relay bottom. Most standard automotive relays have terminals labeled or arranged in a standard pattern:
      • 85 & 86: These are the coil terminals (lower current control circuit).
      • 30: Common terminal (connected to battery power source via a fuse).
      • 87: Normally Open (NO) terminal (connects to 30 when coil is energized - this sends power to the fuel pump).
      • 87a: Normally Closed (NC) terminal (not always present; connects to 30 when coil is de-energized. Usually not used in fuel pump circuits).
    • Set your multimeter to measure resistance (Ohms Ω).
    • Measure resistance between terminals 85 and 86. You should read a relatively low resistance, typically between 50 and 150 Ohms. This indicates the coil winding is intact. An infinite reading (OL) means the coil is open and the relay is dead. A zero reading indicates a shorted coil.
    • Measure resistance between terminals 30 and 87. You should read infinite resistance (OL) when the relay is not energized. This confirms the contacts are open.
    • Testing Coil Activation & Contact Closure: This requires a 12V power source (like a small 12V battery or power supply) and your multimeter.
      • Connect the positive (+) lead from your 12V source to terminal 86.
      • Connect the negative (-) lead from your 12V source to terminal 85. You should hear and feel a distinct click as the relay energizes.
      • While keeping the 12V connected to 85 and 86, measure resistance between terminals 30 and 87. It should now read very low resistance (near 0 Ohms), indicating the contacts have closed. If it still reads OL, the contacts are faulty.
    • If the relay fails any of these tests, it needs replacement.

Step-by-Step Guide to Replacing the Fuel Pump Relay

Once you've confirmed the relay is faulty, replacing it is simple:

  1. Disconnect Battery: Always start by disconnecting the negative battery terminal for safety.
  2. Locate Relay: Access the passenger footwell fuse block and identify the faulty fuel pump relay socket using the methods described earlier.
  3. Remove Old Relay: Firmly grasp the relay and pull it straight out of its socket. Avoid excessive wiggling or pulling on the wires.
  4. Obtain Replacement: Purchase a new relay. The correct part number is crucial. Common original GM part numbers for this era include:
    • GM #25517647 (common replacement number)
    • GM #12020856
    • Standard Motor Parts RY-134 (Aftermarket equivalent)
    • ACDelco D1742A (Aftermarket equivalent)
    • BWD R3124 (Aftermarket equivalent)
    • Always double-check compatibility for a 1985 Camaro. Bring the old relay to the parts store if possible for visual matching. Ensure the terminal configuration (number and layout) matches exactly.
  5. Install New Relay: Align the new relay correctly with the socket (look for orientation tabs or mismatched terminal sizes). Push it firmly and evenly into the socket until it clicks or is fully seated.
  6. Reconnect Battery: Reattach the negative battery cable and tighten the clamp bolt securely.
  7. Test Operation: Turn the ignition key to the "Run" position. You should hear the fuel pump prime for about 2 seconds. If you do, the relay is functioning correctly. Attempt to start the engine.

Understanding the Fuel Pump Circuit

Knowing the relay's role within the larger circuit aids diagnosis:

  1. Power Source: Battery voltage flows through a fuse (often a 20A fuse labeled "FP" or "ECM B" in the underhood fuse box or sometimes on the same passenger fuse block) to relay terminal 30.
  2. Control Signal: When the ignition is turned to "Run" or "Start," the PCM (or fuel pump control module) provides a ground path on terminal 85 of the relay. Terminal 86 typically receives constant battery power (often via another fuse).
  3. Relay Activation: The ground on 85 completes the circuit through the relay coil (between 85 and 86), creating an electromagnetic field.
  4. Contact Closure: This magnetic field pulls internal contacts closed, connecting terminal 30 (power in) to terminal 87 (power out).
  5. Power to Pump: Voltage now flows from terminal 87, through wiring harnesses, to the electric fuel pump located inside the fuel tank. The pump runs, pressurizing the fuel system.
  6. Ground Completion: The fuel pump itself is grounded, usually via a wire attached to the vehicle chassis near the fuel tank, completing the circuit.

Troubleshooting Beyond the Relay

If replacing the relay doesn't solve the problem, other components in the circuit need checking:

  1. Check the Fuel Pump Fuse: Locate the fuse protecting the fuel pump circuit. This is usually a 20-amp fuse. Common locations:
    • Underhood Fuse Box: Often labeled "FP," "FUEL PMP," "ECM B," or "PCM."
    • Passenger Compartment Fuse Block: Sometimes located here, labeled similarly.
    • Visually inspect the fuse. A blown fuse will have a broken metal element visible through the clear plastic top. Replace with a fuse of the exact same amperage rating. If the new fuse blows immediately, there's a short circuit in the wiring or the pump itself is shorted.
  2. Inspect Wiring: Visually check the wiring harness near the relay socket, along the path to the fuel pump (especially where it passes through the firewall and along the frame rail to the tank), and at the fuel pump connector itself for any obvious damage, chafing, corrosion, or disconnections.
  3. Test for Power at the Relay Socket:
    • Reconnect the battery.
    • With the relay removed and ignition in "Run," use a multimeter set to DC Volts.
    • Check for battery voltage between terminal 30 in the socket and ground (a clean metal part of the chassis). You should see ~12V. If not, the fuse or wiring from the battery to terminal 30 is faulty.
    • Check for battery voltage between terminal 86 in the socket and ground. You should see ~12V (constant power for the coil). If not, trace that circuit back (check fuse if applicable).
    • Check for ground signal on terminal 85: Set multimeter to DC Volts. Place the red probe on terminal 85, black probe on ground. With ignition in "Run," you should see battery voltage (~12V) momentarily (during the prime cycle). Alternatively, set multimeter to Ohms. Place one probe on terminal 85, the other on ground. With ignition off, you should see infinite resistance (OL). With ignition on, you should see low resistance (near 0 Ohms), indicating the PCM is providing a ground path. If you don't get the expected ground signal on 85, the issue could be with the PCM, its wiring, or the ignition switch.
  4. Test for Power at the Fuel Pump Connector: This requires accessing the pump connector, usually near the top of the fuel tank or under the rear of the car. Disconnect the electrical connector to the pump. Turn ignition to "Run." Use a multimeter (DC Volts) to check for ~12V between the power wire terminal in the harness connector (consult wiring diagram for exact pin) and ground. If voltage is present during the prime cycle, the pump itself is likely faulty. If no voltage is present, the wiring between the relay (terminal 87) and the pump is faulty.
  5. Check the Fuel Pump Ground: Locate the ground wire connection point for the fuel pump (often near the fuel tank). Ensure the connection is clean, tight, and free of corrosion. Test continuity between the ground terminal on the pump harness connector and the vehicle chassis (should be near 0 Ohms).
  6. Fuel Pump Inertia Switch (If Equipped): Some later third-gen Camaros (though less common on 1985 models) might have an inertia safety switch that cuts power to the pump in an accident. Know if your car has one (consult manual) and check if it's been tripped (usually has a reset button on top).
  7. Fuel Pump Itself: If power and ground are confirmed at the pump connector during the prime cycle, but the pump doesn't run, the pump motor is likely defective and requires replacement.

Choosing a Replacement Relay: OEM vs. Aftermarket

  • OEM (Original Equipment Manufacturer): GM Genuine Parts (ACDelco) relays offer guaranteed compatibility and reliability, matching the original specifications exactly. They are typically the most expensive option but provide peace of mind.
  • Major Aftermarket Brands (Standard Motor Products, BWD/Standard Ignition, ACDelco Professional/Gold): These are reputable brands that produce high-quality relays meeting or exceeding OEM specifications. They offer a good balance of reliability and cost savings compared to dealer parts. Ensure the part number matches your application.
  • Economy Aftermarket/Generic Relays: These are the cheapest options. While they might work initially, quality control can be inconsistent, and they may not have the same durability or precise electrical characteristics as OEM or major brands. Reliability can be a gamble. For a critical component like the fuel pump relay, investing in a known quality brand is recommended.

Preventative Maintenance and Tips

  • Keep Connections Clean: Periodically inspect the relay socket and terminals for corrosion or dirt. A small amount of electrical contact cleaner can be used if needed.
  • Avoid Moisture: While inside the cabin, the fuse block area is generally protected, but leaks or high humidity can contribute to corrosion over time.
  • Carry a Spare: Given its critical role and relatively low cost, carrying a known-good spare relay in your glove box is excellent insurance against being stranded.
  • Quality Matters: When replacing, opt for a relay from a reputable brand (OEM or major aftermarket) to ensure longevity and reliability.
  • Check Related Fuses: When checking the fuel pump relay, it's good practice to also inspect the main engine/power relay fuse and other related fuses in both the underhood and passenger compartment boxes.

Conclusion

Locating the fuel pump relay in your 1985 Camaro under the passenger side dashboard is straightforward once you know where to look. By understanding its function, recognizing symptoms of failure, knowing how to test it, and following the replacement steps, you can quickly diagnose and resolve a common cause of fuel delivery failure. Remember to always prioritize safety by disconnecting the battery before working on electrical components and to use quality replacement parts. With this knowledge, you can keep your classic Camaro running smoothly.

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