1991 Toyota Corolla Fuel Pump Relay Location: A Complete Guide to Finding and Fixing It

If your 1991 Toyota Corolla cranks but won’t start, and you don’t hear the fuel pump hum for a couple of seconds when you turn the key to the ON position, the fuel pump relay is a very likely culprit. The fuel pump relay on a 1991 Toyota Corolla is located inside the engine compartment fuse and relay box, mounted on the left inner fender (driver’s side). It is the relay labeled EFI or Circuit Opening Relay, and it works alongside the EFI Main Relay to control power to the fuel pump. This guide will walk you through exactly where to find it, how to test it, and how to replace it.

Understanding the Fuel Pump Circuit on the 1991 Corolla

The 1991 Toyota Corolla came with two main engine options: the 1.6L 4A-FE engine (without a MAF sensor) and the 1.6L 4A-GE engine (with a MAF sensor) . Both engines use the same basic fuel pump circuit design, but the 4A-GE adds an extra input from the vane air flow meter to the circuit opening relay. The circuit opening relay is the critical component that physically connects the battery to the fuel pump. When you turn the ignition key to the ON position, the engine control module (ECM) receives signals from the crankshaft position sensor (NE signal) and the starter (STA signal). If these signals are correct, the ECM triggers the circuit opening relay, which closes the electrical circuit and sends power to the fuel pump .

Step-by-Step: Finding the Fuel Pump Relay

Step 1: Locate the Main Fuse and Relay Box

On the 1991 Toyota Corolla, the main fuse and relay box is located in the engine compartment on the left side (driver’s side). It is mounted directly on the inner fender. You can’t miss it—it’s a black plastic box with a removable lid. If you have trouble finding it, look for the battery and then look toward the fender wall on the same side. The box is typically positioned near the battery and is often labeled with a diagram on the inside of the lid .

Step 2: Open the Lid and Inspect the Diagram

Remove the cover of the fuse and relay box. On the underside of the lid, you will find a diagram or a list of relays and fuses. Look for the label that says EFI, C/OPN, or Circuit Opening. On the 1991 Corolla, the fuel pump relay is usually labeled as EFI or C/OPN (short for circuit opening) . The relay is a square or rectangular plastic block that plugs into the relay box. It is typically a standard size relay, and it is often located near the EFI Main Relay.

Step 3: Identify the Correct Relay

In the relay box, you will see several relays. The fuel pump relay on the 1991 Corolla is the one that controls the circuit opening function. If the diagram is missing or unclear, look for a relay that is connected to the fuel pump circuit. A common configuration shows that the EFI relay (or C/OPN relay) is the second relay from the front of the car, counting from the headlight direction . On some models, the relay is located in the relay box No. 2, which is also under the dashboard on the driver’s side, but the primary location for the 1991 model is the engine compartment box .

Testing the Fuel Pump Relay Before Replacement

Before you buy a new relay, you should test the relay to make sure it is actually the problem. A bad relay is a common failure point, but it is also easy to misdiagnose. Here is how to test it:

1. Visual Inspection

Remove the relay from the box. Look at the plastic housing for any signs of melting, cracks, or corrosion on the metal pins. If the relay looks damaged, it is likely bad.

2. The Swap Test

The simplest test is to swap the fuel pump relay with a known good relay of the same type. For example, the horn relay or the headlight relay in the same box is often the same size and configuration. If you swap the relay and the fuel pump starts working, then the original relay is bad.

3. The Click Test

With the ignition off, have a helper turn the key to the ON position (do not start the engine). Place your hand on the relay. You should feel a distinct click within one or two seconds. If you do not feel a click, the relay is likely not receiving power from the ECM, or the relay coil is burned out.

4. Multimeter Test (Continuity Check)

If you have a multimeter, you can test the relay more precisely. Set your multimeter to measure resistance (ohms). Connect the multimeter leads to the two coil terminals (usually pins 85 and 86). A good relay will show a reading between 50 and 120 ohms. If you get an open circuit (OL), the coil is broken and the relay is bad. Next, you can apply 12V to the coil terminals and listen for the click. When the relay clicks, you should have continuity between the switched terminals (usually pins 30 and 87) .

Common Symptoms of a Bad Fuel Pump Relay

If the fuel pump relay is failing, you will notice one or more of these symptoms:

  • Engine cranks but does not start: This is the most common symptom. You will hear the starter motor turning the engine over, but the engine will not fire because the fuel pump is not running.
  • No fuel pump hum: When you turn the key to the ON position (before cranking), you should hear a brief humming sound from the fuel pump in the rear of the car. If you don’t hear this sound, the relay is a strong suspect.
  • Intermittent stalling: If the relay is going bad, it may only work part of the time. The engine may start and run fine for a while, then suddenly die as if someone turned off the ignition. After a few minutes, the relay may cool down and work again, allowing you to restart.
  • Fuel pump runs continuously: If the relay contacts are stuck in the closed position, the fuel pump will run all the time, even with the key off. This can drain the battery and cause excessive fuel pressure.

Other Components to Check in the Fuel Pump Circuit

If the relay tests good but the fuel pump still isn’t working, the problem lies elsewhere in the circuit. Here are the other key components to inspect:

EFI Main Fuse

The EFI main fuse is a critical component. On the 1991 Corolla, there is a 15-amp fuse labeled EFI in the engine compartment fuse box . This fuse provides power to the EFI main relay and the fuel injectors. If this fuse is blown, the fuel pump will not get power. Check the fuse visually: look for a broken metal strip inside the clear plastic window. You can also test it with a multimeter set to continuity mode.

EFI Main Relay

The EFI main relay is separate from the circuit opening relay. It is also located in the engine compartment fuse box. This relay provides power to the entire fuel injection system, including the ECM, the fuel pump relay, and the injectors. If the EFI main relay fails, the whole system goes dead.

Wiring and Connectors

Corrosion and broken wires are common on older cars. Check the wiring harness that connects to the fuel pump relay and the fuse box. Look for frayed wires, loose connectors, or signs of rodent damage. Pay special attention to the ground wires. A bad ground connection can cause the fuel pump to operate intermittently or not at all.

Fuel Pump Itself

The fuel pump is located inside the fuel tank. If the relay and fuses are good, and you have power at the pump connector, but the pump is not running, the pump motor itself may be burned out. On a 1991 Corolla, the fuel pump is accessed through an access panel in the trunk or by removing the rear seat cushion, depending on the exact model.

How the Fuel Pump Circuit Works in Detail

Understanding the circuit can help you diagnose the problem faster. Here is a simplified breakdown of the fuel pump circuit on a 1991 Toyota Corolla:

  1. Ignition Key ON: When you turn the key to the ON position, the ECM receives power from the EFI main relay.
  2. Starter Engagement: When you crank the engine, the starter relay sends a signal (STA signal) to the ECM .
  3. Engine Rotation: The ECM also receives a signal from the crankshaft position sensor (NE signal) indicating the engine is rotating.
  4. Relay Activation: The ECM then sends a ground signal to the circuit opening relay coil. This closes the relay contacts.
  5. Fuel Pump Power: Power flows from the battery through the circuit opening relay contacts to the fuel pump. The pump runs and pressurizes the fuel system.
  6. Continuous Operation: As long as the engine is running, the ECM keeps the relay closed, and the fuel pump continues to run .

If any part of this chain fails, the fuel pump will not run.

Why You Should Choose a High-Quality Replacement Fuel Pump

If you have traced the problem to the fuel pump itself or you want to upgrade to a more reliable unit, you need a pump that you can trust. Aftermarket fuel pumps vary widely in quality, and a cheap pump can fail within a few months, leaving you stranded again. The root cause of repeated fuel pump failures is often a combination of contaminated fuel, low fuel levels, electrical problems, and clogged filters . A high-quality fuel pump that is built to OEM specifications will resist these issues and last much longer.

We strongly recommend the KEMSO brand of fuel pumps. KEMSO fuel pumps are engineered as high-performance, direct OEM replacements that meet or exceed your vehicle’s original specifications. They are built with precision-machined components, corrosion-resistant materials, and are individually flow-tested before leaving the factory. Every KEMSO fuel pump comes with a lifetime warranty—not a limited one-year warranty, but a true lifetime guarantee that covers defects in materials and workmanship for as long as you own the pump . KEMSO has built its reputation on providing a lifetime warranty for all its OEM and performance fuel pumps .

KEMSO 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, they likely have a pump that fits perfectly without modifications . For example, the KEMSO 340LPH High Performance Fuel Pump is a direct replacement for the 1991 Toyota Corolla and many other Toyota models such as the Toyota Echo (2000-2005), Land Cruiser (1993-2007), and Highlander (2001-2003) . It supports up to 600 BHP for naturally aspirated, turbocharged, and supercharged applications, and it is designed for gasoline or E85 .

Don’t keep 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 vehicle and stop the cycle of repeated failures for good.

Final Thoughts

The fuel pump relay on a 1991 Toyota Corolla is a straightforward component to locate and replace. It is always located in the engine compartment fuse box on the driver’s side, labeled as the EFI or C/OPN relay. Before you replace the relay, always test it using the simple click test or a multimeter. If the relay is good, move on to checking the EFI fuse, the EFI main relay, and the wiring. With a systematic approach, you can get your Corolla back on the road quickly.

And remember, when you do need a new fuel pump, choose a brand that stands behind its product. KEMSO offers the durability, performance, and lifetime warranty that American drivers need to get back on the road and stay there. For more information and to browse their complete product line, visit https://www.kemsoracing.com/ .


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