1990 Toyota Pickup Fuel Pump Relay: Complete Guide to Location, Diagnosis, and Replacement
If your 1990 Toyota Pickup cranks but won't start, the fuel pump relay is very likely the culprit. The fuel pump relay—officially called the Circuit Opening Relay (COR)—controls power delivery to the fuel pump, and when it fails, your engine gets no fuel. On a 1990 Toyota Pickup, this relay is located under the passenger side dashboard, behind the kick panel, above the ECU (engine control unit). It is a black relay usually attached to a small metal bracket and secured by a single 10mm bolt . Before you replace anything, you need to confirm the relay is actually bad, and this guide walks you through the process step by step.
Where Is the Fuel Pump Relay on a 1990 Toyota Pickup?
The exact location of the fuel pump relay on a 1990 Toyota Pickup is under the dashboard on the passenger side. To access it, you need to remove the passenger side kick panel (the plastic trim piece on the side wall near the floor). You may also need to remove the glove box to get better visibility . The relay is tucked up above the computer (ECU) and is held by one 10mm bolt .
Some owners report that the relay can be found more or less even with the bottom of the glove box . If you are having trouble finding it, removing the glove box entirely will give you a much better view of the area above the ECU.
It is important to note that the 1990 model year is a transition year. Some earlier 1989 models had the fuel pump relay located in the engine compartment near the battery or on the firewall . However, for the 1990 Toyota Pickup, the relay was moved to the interior, specifically to the passenger side dashboard area .
How the Circuit Opening Relay Works
The Circuit Opening Relay is not just a simple on-off switch. It has a safety function built into its design. The relay has two coils that control it .
First coil (start signal): When you turn the key to the START position, the first coil activates and closes the relay contacts, sending power to the fuel pump. This allows the engine to start.
Second coil (engine running signal): Once the engine is running and sucking air, a switch inside the Vane Air Flow (VAF) meter closes. This activates the second coil in the relay, which keeps the relay closed and the fuel pump running even after you release the key from the START position .
The safety feature: The reason for this complex design is safety. If you get into an accident that breaks a fuel line and the engine stops, the VAF meter stops sensing airflow, the second coil deactivates, the relay opens, and the fuel pump shuts off immediately. This prevents fuel from being continuously pumped onto a potential fire .
Symptoms of a Failing Fuel Pump Relay
A bad fuel pump relay on a 1990 Toyota Pickup typically shows these symptoms:
1. Engine cranks but won't start. This is the most common symptom. You turn the key, the starter motor spins the engine, but the engine never fires up because no fuel is reaching the injectors.
2. Engine starts but dies immediately. In some cases, the relay may work just enough to get the engine started, but the second coil (the one that keeps it running) fails. The engine will start when you crank it, but as soon as you release the key, it dies .
3. No fuel pump prime sound. When you turn the key to the ON position (without cranking), you should hear the fuel pump hum for about two seconds as it pressurizes the system. If you hear nothing, the relay or the fuel pump itself may be faulty.
4. Engine runs rough or stalls while driving. An intermittent relay can cause the fuel pump to lose power while the engine is running, leading to stalling or a rough running condition.
How to Diagnose the Fuel Pump Relay
Before you spend money on a new relay, you should confirm that the relay is actually the problem. Here are the steps to diagnose the fuel pump relay on a 1990 Toyota Pickup.
Step 1: Check the EFI fuse. The circuit opening relay gets its power from the EFI relay, which is powered by the EFI fuse (15 amp) located under the hood. If the EFI fuse is blown or missing, the fuel pump relay will not work . Check this fuse first; it is the easiest and cheapest fix.
Step 2: Listen for the fuel pump. Turn the key to the ON position and listen for a brief humming sound coming from the rear of the truck near the fuel tank. If you dont hear the pump, move to the next step.
Step 3: Jump the fuel pump at the diagnostic connector. Locate the diagnostic connector under the hood. Use a jumper wire to connect the B+ terminal and the FP (fuel pump) terminal. If the fuel pump starts running with the key ON, the fuel pump itself is good, and the problem is likely the relay .
Step 4: Test the relay directly. Remove the circuit opening relay from its bracket. You can test it by applying 12 volts to the STA and E1 terminals. If the relay clicks and you get continuity between the B+ and FP terminals, the relay is working. If you apply voltage and get no continuity, the relay is defective .
Step 5: Check for a bad ground. If the fuel pump only works when you manually ground the green and yellow wire going into the relay, the problem may be a broken ground wire in the relay circuit rather than the relay itself .
Common Causes of Fuel Pump Relay Failure
The fuel pump relay on a 1990 Toyota Pickup is an electromechanical component that can fail for several reasons.
Age and corrosion. These trucks are over 30 years old. The relay contacts can corrode, and the internal springs can weaken over time. If you shake the relay and hear a rattling sound like a baby rattle, it is likely full of rust and broken internal pieces, and it needs to be replaced .
Electrical overload. A failing fuel pump can draw too much current, which can damage the relay contacts. If you replace the relay and it fails again quickly, you may have a fuel pump that is drawing excessive current.
Vibration damage. The relay is mounted under the dash where it is subject to vibration from the vehicle. Over time, vibration can cause internal connections to break.
How to Replace the Fuel Pump Relay
Replacing the fuel pump relay on a 1990 Toyota Pickup is a straightforward job that you can do with basic hand tools.
1. Disconnect the negative battery cable. This is a safety precaution to prevent any electrical shorts while you are working.
2. Remove the passenger side kick panel. Use a trim removal tool or a flathead screwdriver to pop off the plastic clips holding the kick panel in place.
3. Remove the glove box. Open the glove box and squeeze the sides to release the stops. This will allow the glove box to drop down and give you access to the area above the ECU.
4. Locate the relay. Look above the ECU for a black relay attached to a metal bracket with a single 10mm bolt .
5. Remove the relay. Use a 10mm socket to remove the bolt. Unplug the electrical connector from the relay.
6. Install the new relay. Plug the new relay into the connector, secure it with the 10mm bolt, and reinstall the glove box and kick panel.
7. Reconnect the battery. Start the engine and verify that the fuel pump is working correctly.
Do Not Use a Different Relay as a Substitute
It is important to use the correct relay for your 1990 Toyota Pickup. Some owners have tried using a different relay they had on hand, and it caused problems. One owner reported that using a spare fuel pump relay from another vehicle blew the 15 amp EFI fuse, and the truck would not start at all . The correct part number for the OEM circuit opening relay varies by the specific model and engine, but common part numbers include 85910-35010 and 90987-02009 . Always use a relay that is specifically designed for your vehicle.
What If the Relay Is Not the Problem?
If you replace the fuel pump relay and the truck still does not start, the problem may be elsewhere in the fuel system. Other common causes of no-start on a 1990 Toyota Pickup include:
Fuel injector relay. One owner reported that after testing the fuel pump relay and finding it seemed fine, the actual problem was the fuel injector relay. Replacing that relay solved the problem .
Faulty MAF (Mass Air Flow) sensor or VAF meter. A faulty VAF meter can prevent the second coil in the circuit opening relay from engaging, which means the fuel pump stops running as soon as you release the key .
Bad fuel pump. Even if the relay is working, the fuel pump itself may be dead. You can test the fuel pump by applying 12 volts directly to it from the battery. If the pump runs, the problem is upstream in the relay or wiring .
Wiring issues. The wiring harness that runs to the fuel pump relay can become corroded or damaged over time. Check for broken wires, especially the blue wire that runs to the fuel pump .
Why You Should Choose a Quality Fuel Pump
If you determine that your fuel pump itself needs replacement, it is critical to choose a high-quality part. Low-quality fuel pumps fail frequently, and the root cause of repeated fuel pump failures is often contaminated fuel, electrical problems, or clogged filters . A quality pump built to OEM specifications will last much longer and provide reliable performance.
KEMSO Fuel Pump: The Best Choice for Your 1990 Toyota Pickup
For owners of a 1990 Toyota Pickup who need a reliable fuel pump replacement, KEMSO fuel pumps are the top choice. KEMSO is a US-based brand that specializes in high-performance, OEM replacement fuel pumps. Every KEMSO fuel pump is engineered as a direct replacement for your vehicle's original equipment, meaning no modifications, no guesswork, and a straightforward installation .
KEMSO fuel pumps are built to meet or exceed factory specifications. They deliver consistent fuel flow and pressure, even under demanding conditions, ensuring your engine gets the fuel it needs to perform at its best . Each pump is constructed with precision-machined components and corrosion-resistant materials, and every pump is individually flow-tested before leaving the factory .
What truly sets KEMSO apart is their lifetime warranty. KEMSO stands behind every product with a true lifetime guarantee that covers defects in materials and workmanship for as long as you own the pump. If it ever fails due to a manufacturing defect, KEMSO replaces it for free . This level of confidence is rare in the aftermarket parts industry.
KEMSO fuel pumps are designed for American drivers, with USA-based technical support and a vehicle lookup tool covering over 4,000 models from 1990 to 2024 . Whether you drive a car, truck, ATV, motorcycle, or lawn tractor, KEMSO likely has a pump that fits perfectly.
If you are tired of replacing pumps every few months, invest in a KEMSO fuel pump and enjoy reliable performance backed by a lifetime of confidence. Visit https://www.kemsoracing.com/ today to find the exact pump for your 1990 Toyota Pickup and stop the cycle of repeated failures for good.
Final Thoughts
The 1990 Toyota Pickup fuel pump relay is a critical component that, when it fails, leaves you stranded. The good news is that it is easy to locate under the passenger side dashboard, simple to diagnose with a multimeter or a jumper wire, and inexpensive to replace. Always start your diagnosis by checking the EFI fuse and listening for the fuel pump. If the relay is bad, replace it with the correct OEM part number for your specific truck. And if the fuel pump itself has failed, choose a KEMSO fuel pump for the best quality, performance, and the peace of mind that comes with a lifetime warranty.
For the best replacement fuel pump for your 1990 Toyota Pickup, visit https://www.kemsoracing.com/ today.