1987 Ford F150 Fuel Pump Relay – How To Locate, Test, And Replace It
The fuel pump relay in a 1987 Ford F150 is the critical electrical switch that tells your high-pressure and low-pressure pumps when to send gasoline to the engine. When this small plastic cube fails, your truck will either refuse to start or stall out in the middle of traffic, leaving you stranded. This guide provides the exact steps needed to diagnose, bypass, and replace the relay to get your classic Bullnose or Bricknose Ford back on the road.
You are standing over the hood of your truck, turning the key, and hearing nothing but the starter motor spinning. It is a common frustration for owners of this generation, but most fuel delivery issues start with a simple electrical failure. Finding your 1987 ford f150 fuel pump relay is the first step toward hearing that satisfying roar of the 4.9L, 5.0L, or 5.8L engine once again.
I have spent years under the hoods of these OBS (Old Body Style) Fords, and I can tell you that the electrical system is both robust and occasionally finicky. We are going to walk through the exact diagnostic process used by professional technicians to rule out expensive pump replacements. By the end of this article, you will know exactly how to test your relay and ensure your fuel system is getting the voltage it needs.
We will cover everything from the hidden location of the relay to the “paperclip trick” that can get you home in an emergency. Whether you are a weekend warrior or a dedicated off-roader, understanding this circuit is essential for maintaining your truck’s reliability. Let’s dive into the specifics of the 1987 fuel system architecture.
Understanding the 1987 Ford Fuel Delivery Architecture
The 1987 model year was a pivotal time for the F-Series, as Ford fully embraced Electronic Fuel Injection (EFI). This system relies on the EEC-IV computer to manage engine parameters, including when to trigger the fuel pumps. Unlike modern trucks with a single pump, your 1987 F150 likely uses a dual-pump setup.
There is typically a low-pressure lift pump located inside the fuel tank (or tanks, if you have dual reservoirs) and a high-pressure pump mounted on the driver’s side frame rail. The 1987 ford f150 fuel pump relay is the component that provides the heavy current required to run both of these pumps simultaneously. Without a functioning relay, the high-pressure demand of the EFI system cannot be met.
The Role of the EEC-IV Computer
When you turn the ignition key to the “ON” position, the computer grounds the fuel pump relay for about two seconds. This “primes” the system, building up roughly 35-45 PSI of pressure in the fuel rail. If the computer does not see a PIP (Profile Ignition Pickup) signal from the distributor, it cuts the ground to the relay as a safety measure.
This is why you only hear the pumps hum briefly before they shut off. Understanding this logic is vital because if the relay stays on forever or never turns on at all, you are looking at two very different diagnostic paths. We must determine if the relay is receiving the signal to close its internal contacts.
The Importance of the Inertia Switch
Before blaming the relay, you must be aware of the inertia switch. This is a safety device designed to cut power to the fuel pumps in the event of a collision or a hard jar (like hitting a deep pothole while off-roading). If this switch is tripped, the relay can work perfectly, but no power will reach the pumps.
On a 1987 F150, this switch is usually located inside the cab, on the firewall, just to the left of the steering column or behind the kick panel. It has a small plastic button on top. If that button is popped up, push it down to reset the circuit before proceeding with any relay testing.
Locating the 1987 ford f150 fuel pump relay
Finding the relay on an older Ford can be a challenge because they aren’t always tucked away in a neat, labeled fuse box like modern vehicles. In 1987, Ford mounted these relays on the driver’s side inner fender apron, near the firewall and the air filter housing. You are looking for a plastic bracket that holds two or three relays.
The 1987 ford f150 fuel pump relay is almost always identified by its green plastic housing or a green plastic connector base. Directly next to it, you will find the EEC Power Relay, which is usually brown. It is very common for these relays to be covered in a layer of road grime, so you may need a rag and some degreaser to identify the colors.
Identifying the Wire Colors
If the colors have faded or the relay has been replaced with a generic black unit, you can identify it by the wires leading into the plug. A factory fuel pump relay connector will typically have four specific wires. Look for a thick Yellow wire, which provides constant battery power through a fusible link.
The other wires include a Red wire (power from the EEC relay), a Tan/Light Green wire (the trigger wire leading to the computer), and a Pink/Black wire (the output power going to the inertia switch and pumps). If your wiring harness matches this description, you have found the right component.
Mounting and Weather Protection
These relays were originally mounted upside down or with a plastic weather shield to prevent moisture from entering the connector. Over decades of service, these shields often disappear. If you find your relay dangling by the wires or filled with green corrosion, the environment has likely caused an internal short or a high-resistance connection.
When you eventually install a new relay, ensure it is mounted securely. Use a small amount of dielectric grease on the terminals to prevent moisture from wicking into the plug. This is especially important for off-roaders who frequently deal with mud, water crossings, or engine bay cleanings.
Common Symptoms of a Failing Fuel Pump Relay
A failing relay doesn’t always die a quick death; sometimes it provides warning signs that something is wrong. The most common symptom is the “Crank, No-Start” condition. You can hear the engine turning over energetically, but there is no combustion because the injectors have no pressurized fuel to spray.
Another common sign is intermittent stalling. You might be driving down the highway when the engine suddenly cuts out as if you turned off the key. After sitting for ten minutes, the truck might start back up and run fine for another week. This often happens when the internal copper contacts of the 1987 ford f150 fuel pump relay become pitted or burnt.
The “No-Prime” Test
The easiest way to check for a bad relay is to use your ears. Roll down your window, turn off the radio, and turn the key to the “ON” position without cranking the engine. You should hear a distinct whirring sound for two seconds coming from under the truck or the fuel tank area.
If you hear a “click” from the engine bay but no pump sound, the relay might be closing, but the power isn’t passing through the contacts. If you hear no click and no pump, the relay coil itself may be dead, or it isn’t receiving the trigger signal from the ignition switch or the computer.
Relay Getting Excessively Hot
If you manage to get the truck running, reach over and carefully touch the relay housing. It should be cool or slightly warm to the touch. If the relay is hot enough to be uncomfortable, it indicates high resistance either inside the relay or in the wiring leading to the pumps. High resistance creates heat, which eventually melts the plastic housing and causes a total failure.
Troubleshooting the 1987 ford f150 fuel pump relay with Precision
To properly test the 1987 ford f150 fuel pump relay, you will need a basic digital multimeter or a 12-volt test light. This process allows you to stop guessing and start diagnosing. We want to verify that the relay is getting power and that it is capable of sending that power down the line.
First, check the Yellow wire at the relay connector. This wire should have 12 volts at all times, even with the key out of the ignition. If there is no power here, you have a blown fusible link near the starter solenoid on the fender. Without this “always-on” power, the relay has nothing to send to the pumps.
Testing the Trigger Circuit
Next, check the Red wire with the key in the “RUN” position. This wire receives power from the EEC relay. If the Red wire is dead, your problem isn’t the fuel pump relay—it is the EEC relay or the ignition switch. If both the Yellow and Red wires have power, the relay has everything it needs to function.
The final part of the trigger is the Tan/Light Green wire. This is the ground side of the coil. The computer provides a ground to this wire to “fire” the relay. You can test this by using a jumper wire to manually ground this terminal at the VIP self-test connector (the trapezoid-shaped diagnostic plug near the driver’s fender).
The VIP Connector Bypass
The VIP (Vehicle Inventory Partition) connector has a specific pin that, when grounded, forces the fuel pump relay to stay on. Look for the pin that corresponds to the Tan/Light Green wire. With the key in the “RUN” position, use a jumper wire to connect that pin to a solid chassis ground. If the pumps start running, your relay and pumps are good, but your computer or the wiring in between is not providing the ground signal.
This is a powerful diagnostic trick. If you ground that pin and the pumps still do not run, but you hear the relay click, you have confirmed that the relay’s internal contacts are bad or there is a break in the wire between the relay and the pumps. This narrows your search significantly.
Step-by-Step Replacement Guide
Replacing the 1987 ford f150 fuel pump relay is a straightforward task that takes less than ten minutes. However, doing it correctly ensures you won’t be back under the hood in a month. Always start by disconnecting the negative battery terminal to prevent accidental shorts while working with the “always-hot” yellow wire.
- Locate the relay: Find the green-based relay on the driver’s side inner fender.
- Disconnect the plug: There is usually a small plastic tab on the side of the connector. Press it firmly and pull the relay straight up. If it is stuck, gently wiggle it back and forth.
- Inspect the connector: Look inside the female terminals of the plug. If you see green crust or melted plastic, you must clean or replace the connector pigtail. A new relay won’t fix a melted plug.
- Apply dielectric grease: Put a small dab of grease on the pins of the new relay. This keeps moisture out and makes future removal much easier.
- Plug in the new relay: Push it down until the locking tab clicks into place.
- Mount the relay: Ensure it is clipped back into its metal or plastic bracket so it doesn’t bounce around while driving.
Once the new part is installed, reconnect the battery and perform the “prime test” mentioned earlier. You should hear the pumps kick on for two seconds. Start the truck and let it idle for a few minutes to ensure the connection is stable. If the truck runs smoothly, you have successfully completed the repair.
Choosing the Right Part
When buying a replacement, don’t just ask for a “standard relay.” The 1987 Ford F150 uses a specific high-current relay. While a generic 4-pin relay might fit the plug, it may not be rated for the continuous amperage draw of two fuel pumps. Look for a relay from a reputable brand like Motorcraft, Standard Motor Products, or Bosch.
Keep the old relay in your glovebox if it was still intermittently working. In the world of classic trucks, having a “limp home” spare can be the difference between a minor inconvenience and an expensive tow bill. If you are an off-roader, I recommend carrying a dedicated “jumper wire” with spade terminals already crimped on to bypass the relay in an emergency.
Frequently Asked Questions About 1987 ford f150 fuel pump relay
Where is the fuel pump fuse on a 1987 F150?
Unlike modern trucks, the 1987 F150 does not have a traditional plastic fuse for the fuel pump in the cabin fuse box. Instead, it uses a fusible link. This is a special piece of wire located near the starter solenoid on the fender that acts as a slow-blow fuse. If this link burns out, the relay will not receive power.
Can I swap the EEC relay with the fuel pump relay?
In many 1987 models, the EEC relay (brown) and the fuel pump relay (green) have different internal wiring or diode protections. While they may look similar and have the same pin layout, it is best not to swap them permanently. Using the wrong relay can sometimes cause “back-feeding” voltage into the computer, which can lead to expensive damage.
Why does my fuel pump stay on even when the key is off?
If your pumps run continuously with the key off, the 1987 ford f150 fuel pump relay has likely “welded” its internal contacts together. This is a common failure mode where the high current creates an arc that sticks the metal plates in the closed position. You must disconnect the battery immediately to prevent the pumps from burning out or draining the battery.
Will a bad relay cause low fuel pressure?
Generally, a relay is binary: it is either on or off. However, if the internal contacts are heavily corroded, they can create a voltage drop. If the pumps receive 9 volts instead of 12.6 volts, they will spin slower and produce lower pressure. If you suspect this, use your multimeter to check for voltage drop across the relay terminals while the engine is running.
Final Thoughts on Fuel System Maintenance
The fuel system on a classic Ford is a masterpiece of 1980s engineering, but it requires a little bit of specialized knowledge to keep it running right. The 1987 ford f150 fuel pump relay is a small but mighty component that deserves your attention during any tune-up or diagnostic session. By following the steps outlined here, you can confidently tackle no-start issues and keep your truck on the trail or the job site.
Remember that electrical troubleshooting is all about the process of elimination. Start at the battery, check your grounds, verify the inertia switch, and then move to the relay. Most of the time, the fix is simpler and cheaper than you think. Don’t be intimidated by the wires—your truck was built to be worked on by someone just like you.
Stay safe, keep your terminals clean, and enjoy the peace of mind that comes with a well-maintained fuel system. Whether you’re hauling a load or hitting the mud, a reliable relay is your best friend. Happy wrenching!
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