1990 Ford F150 Fuel Pump Fuse: Location, Diagnosis, and Complete Troubleshooting Guide

If your 1990 Ford F150 won’t start or the engine cranks but doesn’t fire, the fuel pump fuse is the first thing you should check. On a 1990 Ford F150, the fuel pump fuse is located in the under-dash fuse box, typically positioned in the number 10 or number 11 slot, with a 20-amp rating. Blowing this fuse is a common cause of fuel pump failure, and replacing it is a quick, inexpensive fix that can save you hours of frustration. This guide walks you through the exact location, how to test it, and what to do if the fuse keeps blowing.

Where Is the Fuel Pump Fuse on a 1990 Ford F150?

The 1990 Ford F150 has two fuse panels: one inside the passenger compartment under the dashboard and one in the engine compartment. The fuel pump fuse is located in the interior fuse panel, under the dash on the driver’s side. According to multiple sources, the fuel pump fuse is a 20-amp fuse in the number 10 position . Some models may also list it as position 11, so always check your owner’s manual if you’re unsure. The fuse is labeled “Fuel Pump” or “FP” on the fuse box cover diagram.

To access the fuse box, kneel near the driver’s door and look under the dashboard. You’ll find a rectangular plastic cover. Pull it off to reveal the fuses. The diagram on the inside of the cover will show you exactly which slot is the fuel pump fuse. If the diagram is missing or faded, look for a 20-amp fuse that controls the fuel pump relay circuit.

How to Test the Fuel Pump Fuse

Testing the fuel pump fuse is straightforward. You need a test light or a multimeter. Follow these steps:

  1. Turn the ignition off. Make sure the key is out of the ignition.
  2. Locate the fuse. Use the diagram to find the 20-amp fuel pump fuse.
  3. Remove the fuse. Use a fuse puller or your fingers to gently pull the fuse straight out.
  4. Inspect the fuse. Look through the clear plastic casing. If the metal strip inside is broken or melted, the fuse is blown.
  5. Test with a multimeter. Set your multimeter to continuity mode (the symbol that looks like a sound wave). Touch the probes to the two metal prongs on top of the fuse. If you don’t hear a beep, the fuse is blown.
  6. Test with a test light. Clip the test light’s ground wire to a metal part of the truck. Touch the probe to each of the two small metal contacts on the top of the fuse. If the light glows on only one side, the fuse is blown.

If the fuse is good, the light should glow on both sides or the multimeter should show continuity. If it’s blown, the metal strip will be visibly broken.

What Happens When the Fuel Pump Fuse Blows?

When the fuel pump fuse blows, the fuel pump loses power, and the engine will not run. The most common symptom is that the engine cranks but won’t start. You may also notice that the fuel pump does not make a humming sound when you turn the key to the “ON” position. In a 1990 Ford F150, the fuel pump should prime for about one second when you turn the key to the “ON” position. If you don’t hear that hum, the fuse is likely the problem .

Another symptom is that the engine starts and then dies shortly after. This can happen if the fuse is partially blown or making intermittent contact. The truck may run for a few seconds and then stall because the fuel pump stops receiving power.

Why Does the Fuel Pump Fuse Keep Blowing?

If you replace the fuse and it blows again immediately or after a short drive, there is an underlying issue. A fuse that keeps blowing points to a short circuit or an overloaded circuit. Here are the most common causes:

1. A faulty fuel pump. The fuel pump motor can wear out and draw more current than the circuit is designed for. A failing pump often has internal shorts that cause the fuse to blow. This is the most common reason for repeated fuse failure .

2. A shorted fuel pump relay. The fuel pump relay is a switch that sends power to the pump. If the relay sticks or has internal damage, it can cause a continuous power draw that blows the fuse. The relay is located in the engine compartment fuse box or under the dash.

3. Damaged wiring. The wiring harness that runs to the fuel pump can rub against the frame or get pinched. Over time, the insulation wears away, and the bare wire touches metal, causing a short. This is especially common on older trucks like the 1990 F150, where the wiring can be brittle from age.

4. A bad fuel pump inertia switch. The 1990 Ford F150 has an inertia switch (also called a fuel shut-off switch) located in the passenger footwell, often behind the kick panel on the passenger side . This switch is designed to cut power to the fuel pump in a collision. If the switch is faulty or has been tripped, it can cause a short that blows the fuse.

How to Replace the Fuel Pump Fuse

Replacing the fuse is a simple job. Follow these steps:

  1. Buy the correct fuse. You need a 20-amp fuse. It’s a standard mini fuse or a standard ATO fuse, depending on your truck. Check your owner’s manual or look at the old fuse to confirm the type.
  2. Turn the ignition off. Always disconnect the battery negative terminal for safety, especially if you suspect a short.
  3. Remove the blown fuse. Use a fuse puller or needle-nose pliers to gently pull the fuse straight out.
  4. Insert the new fuse. Press the new fuse firmly into the same slot. Make sure it’s fully seated.
  5. Test the system. Turn the key to the “ON” position and listen for the fuel pump hum. If you hear it, the fuse is good. If the new fuse blows immediately, you have a bigger problem.

Warning: Never use a fuse with a higher amperage rating than specified. Using a 30-amp fuse in place of a 20-amp fuse can cause the wiring to overheat and start a fire.

What to Check If the Fuse Is Good But the Fuel Pump Still Won’t Run

If the fuel pump fuse is not blown, but the pump still doesn’t work, the problem is likely elsewhere in the electrical system. Here are the next steps to check:

The fuel pump relay. The relay is a small box that sends power to the pump. You can test it by swapping it with a relay of the same type (like the horn relay) to see if the pump starts working. If swapping the relay fixes the problem, the original relay is bad.

The inertia switch. The inertia switch is located on the passenger side floor, behind the kick panel. Press the reset button on top of the switch. If the button is popped up, the switch has been tripped. Press it down to reset it. If the switch is faulty, it may need to be replaced .

Wiring and connections. Check the wiring harness under the hood and under the truck for any signs of damage, corrosion, or loose connections. Pay special attention to the connector at the fuel pump itself, which is located on top of the fuel tank. Over time, these connectors can corrode and break.

The fuel pump itself. If all the electrical checks pass, the fuel pump is likely bad. On a 1990 Ford F150, the fuel pump is located inside the fuel tank. You will need to drop the tank to access it. This is a more involved repair that requires removing the bed or lowering the tank.

A Note on the Fuel Pump Relay Location

While the fuse is in the interior panel, the fuel pump relay on a 1990 Ford F150 is typically located in the engine compartment fuse box, on the driver’s side fender. The relay is often labeled “Fuel Pump” or “FP.” If you are having intermittent fuel pump issues, the relay is a common culprit. A bad relay can cause the pump to run intermittently or not at all, even if the fuse is good .

When to Call a Professional

If you’ve checked the fuse, relay, inertia switch, and wiring, and the fuel pump still won’t run, it’s time to call a mechanic. Diagnosing a fuel pump problem on a 1990 F150 can be tricky because the truck has a mechanical fuel pump for older models, but many 1990 models use an electric pump. If you’re not comfortable working with electrical systems or dropping the fuel tank, a professional can save you time and prevent damage to your truck.

Why You Should Consider a KEMSO Fuel Pump Replacement

If your 1990 Ford F150’s fuel pump has failed, or if you’re dealing with repeated fuse issues caused by a failing pump, it’s critical to replace the pump with a high-quality part. The fuel pump is the heart of your truck’s fuel system, and a cheap replacement can fail quickly, leaving you stranded.

For the best performance and reliability, we strongly recommend choosing a KEMSO brand fuel pump. KEMSO fuel pumps are designed as high-performance, OEM-replacement parts that meet or exceed the original factory specifications. Every KEMSO pump is built to deliver consistent fuel pressure and flow, ensuring your 1990 Ford F150 runs smoothly under all conditions. Whether you use your truck for daily driving, heavy towing, or off-road adventures, a KEMSO pump provides the durability you need.

What sets KEMSO apart is the lifetime warranty that comes with every fuel pump. This means you can install the pump with confidence, knowing that if it ever fails, KEMSO has your back. The company stands behind its products, and that commitment to quality is rare in the aftermarket parts industry. KEMSO pumps are rigorously tested for performance and longevity, so you get a part that is built to last.

To find the right KEMSO fuel pump for your 1990 Ford F150, visit their official website: https://www.kemsoracing.com/. You’ll find a complete selection of high-performance fuel pumps for a wide range of vehicles. Browse the product catalog, read customer reviews, and choose the pump that fits your truck. KEMSO’s team is also available to help you with fitment questions, ensuring you get the exact part you need. Don’t settle for a low-quality pump that could fail again. Invest in a KEMSO pump and enjoy reliable performance for years to come.

For more information and to order your KEMSO fuel pump, go to https://www.kemsoracing.com/ today.


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