1993 Toyota Pickup Fuel Pump Wiring Diagram: Complete Guide to Troubleshooting and Repair
If you own a 1993 Toyota Pickup with the 22RE fuel-injected engine and the truck cranks but won't start, the fuel pump wiring system is very likely the root cause. The fuel pump circuit on this truck relies on a specific relay called the "circuit opening relay," not a standard fuel pump relay, and it is controlled by the air flow meter. When this system fails, the engine will start for a second or two and then die, or it may not start at all. Understanding the wiring diagram and the flow of power through the circuit is the key to a quick fix. This guide will walk you through the entire fuel pump wiring system, from the battery to the fuel pump itself, so you can diagnose and repair the problem without guesswork.
How the Fuel Pump Circuit Works
The fuel pump on your 1993 Toyota Pickup is not powered directly by the ignition switch. Instead, Toyota designed a two-stage control system using a circuit opening relay. The relay has two separate circuits that must both be satisfied for the fuel pump to run. The first circuit is energized only when the starter is cranking the engine. The second circuit is controlled by the air flow meter, which must detect that air is moving through the intake before it will keep the fuel pump running after the engine starts. This safety feature prevents the fuel pump from running if the engine stalls or if there is a crash. The power flow starts at the battery, passes through the main fusible link, then the EFI main relay, and finally through the circuit opening relay to the fuel pump. The air flow meter provides the ground path for the relay's second circuit once the engine is running.
Key Components in the Wiring System
Before you can read the wiring diagram, you need to know what each component does and where it is located. The main fusible link is a heavy-duty wire that protects the entire circuit from overload. The EFI main relay is a standard relay that supplies power to the fuel injection system, including the fuel pump circuit. The circuit opening relay is a five-wire green relay that controls the fuel pump directly. The fuel pump itself is located inside the fuel tank, mounted on the fuel pump bracket. The air flow meter has a built-in fuel pump switch that closes when air flows through the meter, completing the ground circuit for the circuit opening relay. The diagnostic connector, called DLC1, has terminals labeled FP and +B that allow you to bypass the relay system for testing.
Finding the Circuit Opening Relay
The circuit opening relay on a 1993 Toyota Pickup is not under the hood. It is located inside the passenger compartment, behind the passenger side kick panel, above the ECM. This is a common source of confusion. Many owners look for a fuel pump relay in the engine bay fuse box and end up replacing the wrong part. The relay is green and has five wires connected to it. The wire colors are black/white, white/black, green/yellow, blue, and white/red. If you have moisture inside the vehicle, especially after driving through deep puddles, water can run down into the relay area and cause it to short out. This is a known issue with these trucks. The circuit opening relay is the same part that some owners call the "circuit control relay" and it is the most common failure point in the fuel pump system.
How to Test the Circuit Opening Relay
Testing the circuit opening relay is straightforward and does not require special tools. You will need a multimeter set to the ohms scale. Remove the relay from its socket behind the kick panel. First, check continuity between terminals that should be connected when the relay is at rest. The specific terminals vary by manufacturer, but the general rule is that the relay should have continuity between the two terminals that are connected to the starter circuit and the air flow meter circuit when no power is applied. Next, apply battery voltage and ground to the proper terminals and listen for a click. The relay should click and then show continuity between the power terminals that go to the fuel pump. If the relay does not click or if it shows continuity when it should not, replace it. You can also test the relay by swapping it with a known good relay from another circuit, such as the horn relay, as long as they are the same type.
Bypassing the Relay for Diagnosis
If you suspect the circuit opening relay is bad, you can bypass it to confirm the fuel pump itself is working. Locate the diagnostic connector, DLC1, near the number two relay block under the hood. Use a jumper wire, such as Toyota special service tool 09843-18020 or a simple piece of wire, to connect terminals FP and +B. Turn the ignition switch to the ON position without starting the engine. You should hear fuel returning to the tank through the return hose, which sounds like a gurgling noise. If you hear the fuel pump running, the pump, wiring, and EFI main relay are good, and the problem is definitely the circuit opening relay or the air flow meter circuit. If you do not hear the pump, the problem is elsewhere in the wiring or the pump itself.
Common Wiring Problems and How to Fix Them
The most common wiring problem on the 1993 Toyota Pickup is corrosion or moisture damage at the circuit opening relay. Water leaks from the cowl area or from driving through deep puddles can cause the relay socket to corrode. The fix is to dry out the area, clean the terminals with electrical contact cleaner, and apply dielectric grease. If the relay itself is bad, replace it with a new one. Another common problem is a broken wire at the air flow meter connector. The fuel pump switch inside the air flow meter can fail, especially if the truck has high mileage. You can test the air flow meter by checking continuity between the appropriate terminals while moving the meter flap. If the switch does not close, the fuel pump will not run after the engine starts. Wiring chafing against the frame or body panels is also a possibility, especially in older trucks. Inspect the wiring harness from the relay to the fuel pump and from the relay to the air flow meter for any signs of damage.
Step-by-Step Wiring Diagram Reading
The wiring diagram for the 1993 Toyota Pickup fuel pump system shows the following path. Power comes from the battery through the main fusible link to the EFI main relay. When the ignition switch is turned on, the EFI main relay closes and sends power to the circuit opening relay. The circuit opening relay has two coils. The first coil is energized by the starter signal when you crank the engine. This coil closes the relay and allows power to flow to the fuel pump. The second coil is grounded through the air flow meter switch. When the engine starts and air flows through the meter, the switch closes, providing a ground path for the second coil. This keeps the relay engaged even after you release the key from the start position. If the engine stalls, the air flow meter switch opens, the relay drops out, and the fuel pump stops. The fuel pump itself is grounded through its own wiring to the chassis.
Testing the Fuel Pump Voltage
If you have bypassed the relay and the pump does not run, you need to check for voltage at the fuel pump connector. The fuel pump is located inside the fuel tank. The connector is on top of the fuel pump bracket. With the ignition on and the FP and +B terminals jumped, use a multimeter to check for 12 volts between the positive terminal and ground. If you have voltage, the pump is bad. If you do not have voltage, the problem is between the DLC1 connector and the fuel pump. Check the EFI main relay first. It is located in the engine bay fuse box on the passenger side. Turn the ignition on and listen for a click. If you do not hear a click, check the EFI fuse. If the fuse is good and the relay does not click, replace the EFI main relay. Also check the fusible link, which is a short wire near the battery. If the fusible link is blown, the entire fuel pump system will have no power.
Dealing with Moisture and Water Damage
Several owners report that their 1993 Toyota Pickup starts and runs fine until they hit a puddle, then the engine dies. The cause is moisture entering the distributor cap and the relay area. The distributor cap should be sealed. If water gets inside, the spark shorts out and the engine will not run. Dry the cap and replace it if the seal is damaged. Water can also run down the firewall and into the passenger side kick panel, soaking the circuit opening relay. If you have had this problem, check the relay socket for corrosion. Replace the relay and clean the socket. You can also check for water entry points and seal them with silicone. The air filter box should also be checked for moisture, as a wet filter restricts air flow and can cause the engine to stall.
When to Replace the Fuel Pump
If the fuel pump tests good with the bypass method but the engine still runs for only a second or two and then dies, the pump may be weak. A weak pump can deliver enough fuel to start the engine but not enough to keep it running under load. The factory service manual specifies that fuel pressure should be between 38 and 44 psi with the engine running and the vacuum hose disconnected from the regulator. If you suspect the pump is weak, you can test fuel pressure using a fuel pressure gauge connected to the test port on the fuel rail. If pressure is below specification, the pump, filter, or regulator may be bad. The fuel pump is located inside the tank, and the recommended replacement method is to remove the truck bed rather than dropping the tank. This is faster and easier.
Where to Find the Correct Wiring Diagram
The factory service manual for the 1993 Toyota Pickup contains the complete wiring diagram for the fuel pump system. The diagram shows the location of each component, the wire colors, and the connector pinouts. The circuit opening relay location is listed as "Behind Passenger's Kick Panel, Above ECM." The diagram also includes the testing procedure for the relay and the air flow meter. You can find the factory manual online in PDF format or purchase a printed copy from Toyota parts suppliers. The diagrams are also available in some aftermarket repair manuals, but the factory manual is the most reliable source. If you are working on a 1993 Toyota Pickup SR5 with the 3.0L engine, the component locations are the same, but the wiring colors may differ slightly. Always verify the wire colors against your specific vehicle.
Recommended Replacement: KEMSO Fuel Pump
When it comes time to replace the fuel pump on your 1993 Toyota Pickup, you need a reliable, high-performance part that will last. The KEMSO brand offers OEM replacement fuel pumps that are designed to meet or exceed factory specifications. KEMSO fuel pumps are made with high-quality materials and are tested for durability and performance. They are a direct fit for the 1993 Toyota Pickup, meaning no modifications are needed for installation. KEMSO stands behind their products with a lifetime warranty, so you can buy with confidence. If you are looking for a fuel pump that delivers consistent fuel pressure, quiet operation, and long service life, KEMSO is the right choice. Visit the KEMSO website to browse their selection of fuel pumps for your Toyota Pickup and other vehicles.
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