The Complete Guide to 1990 Toyota Pickup Fuel Pump Wiring: Diagrams, Circuits & Fixes

Finding an accurate 1990 Toyota Pickup fuel pump wiring diagram is crucial because the exact circuit path depends heavily on whether you have a Standard Cab or Xtracab, and whether your engine is carbureted or Fuel Injected (EFI). This guide provides precise, model-specific wiring information, troubleshooting steps, and essential safety warnings to diagnose and fix your fuel pump electrical problems yourself. Forget generic diagrams; we break down the specifics for your 1990 Toyota Pickup.

Getting your 1990 Toyota Pickup back on the road often starts with diagnosing a fuel delivery issue, and a malfunctioning fuel pump circuit is a prime suspect. While the core function – delivering power from the battery to the pump – seems simple, the exact wiring path in your specific 1990 Pickup is not universal. This isn't about complex theories; it's about knowing where the electricity flows specifically in your truck. The critical factors determining the correct wiring path are the Cab Style (Standard Cab or Xtracab) and the Fuel System Type (Carbureted 22R or Fuel Injected 22RE). Using a diagram meant for the wrong configuration can lead you astray, wasting time and potentially causing further problems. Understanding these differences is the foundation of successful diagnosis and repair.

Safety First: Non-Negotiable Precautions

Before touching a single wire in your 1990 Pickup, adhere to these essential safety rules:

  1. Disconnect the Battery: Always disconnect the NEGATIVE (-) battery terminal before beginning any electrical work. Store it away from the post to prevent accidental contact.
  2. No Smoking or Open Flames: Fuel vapors are present around the pump and lines. A single spark can ignite them, causing severe injury or death. Work in a well-ventilated area.
  3. Relieve Fuel System Pressure: For EFI models (22RE), fuel pressure can exceed 40 PSI. Attempting to disconnect lines without relieving pressure can spray fuel uncontrollably. Locate the fuel pressure pulsation damper (often near the cold start injector on the fuel rail), cover it with shop towels, and carefully loosen the bolt connecting it to the fuel rail slightly to allow pressure to bleed off before fully disconnecting any pump-related lines or the pump itself. Have rags ready to catch fuel.
  4. Secure the Vehicle: Ensure the truck is parked on a level surface with the parking brake firmly engaged. Use wheel chocks.
  5. Fire Extinguisher: Have a suitable fire extinguisher rated for gasoline fires readily accessible near your workspace.

Identifying Your 1990 Toyota Pickup Configuration

Your first step is determining exactly which setup you have:

  • Cab Style: Look at the area behind the driver and passenger seats. A Standard Cab has a single row of seats and a small, non-accessible space behind them. An Xtracab has access doors behind the main doors, leading to a small storage/jump seat area. The fuel pump location differs significantly between these cab styles.
  • Fuel System:
    • Carbureted (22R Engine): Look at the top of the engine. A carburetor is a distinct metal component bolted directly to the intake manifold, usually with a round air cleaner housing on top. Vehicles with manual transmissions were typically carbureted in 1990. Check your VIN or engine designation; the "R" suffix often indicates carbureted.
    • Fuel Injected (22RE Engine): Look for a large plastic or metal air intake tube running from the air cleaner box to a throttle body bolted onto the intake manifold. There is no traditional carburetor. Vehicles with automatic transmissions were typically fuel injected (22RE) in 1990. The "E" suffix usually denotes EFI.

Fuel Pump Location Depends on Cab Style

  • Standard Cab: The fuel pump is located inside the primary fuel tank itself. Access requires dropping the fuel tank (a major job).
  • Xtracab: The fuel pump is located in a dedicated cavity mounted on the outside frame rail on the driver's side, positioned roughly below the driver's seat (or the driver's-side jump seat). It is housed in a protective metal case and accessed relatively easily from underneath the truck without dropping the tank. This distinction is crucial for testing and accessing the pump's wiring connector.

Core Components of the 1990 Toyota Pickup Fuel Pump Circuit

Regardless of cab style or fuel system, several key components are involved in getting power to the pump:

  1. Battery: The primary source of electrical power.
  2. EFI Main Relay (EFI Models) / Circuit Opening Relay (Carb Models - if equipped): This relay is the master switch controlled by the ignition and other signals. Location: Typically found inside the cabin, under the dashboard on the driver's side, often near the steering column or fuse box. It might be clipped to metal brackets or bolted in place. In some 22RE trucks, it might also be located in the engine bay fuse/relay box. Function: It receives a switching signal (often from the ignition switch) and also a signal confirming the engine is cranking or running (like from the ignition coil or engine control unit - ECU). Only when both signals are present does it send main battery power down the circuit towards the pump. Its failure prevents pump operation.
  3. Fuel Pump Relay (Primarily EFI Models, sometimes Carb): While the EFI Main Relay often provides the main switched power source via the engine run signal, a dedicated Fuel Pump Relay further controls the circuit on many EFI models. Its operation is often directly controlled by the ECU based on engine signals. Location: Usually found near the EFI Main Relay under the dashboard or within the engine compartment fuse/relay box. Function: The ECU grounds the relay's control coil when it detects the engine is cranking or running (e.g., via the NE signal from the distributor). This closes the relay contacts, allowing power from the EFI Main Relay (or sometimes directly from the ignition switch circuit) to reach the fuel pump circuit.
  4. Ignition Switch: Initiates the signal path to activate the EFI Main Relay/Fuel Pump Relay when turned to the "ON" or "START" position.
  5. Engine Control Unit (ECU - 22RE EFI Models ONLY): The computer that manages engine functions. It monitors inputs (like crank/cam position, airflow) and controls outputs, including grounding the Fuel Pump Relay coil to activate the pump. It also monitors pump operation via circuitry. It stores Diagnostic Trouble Codes (DTCs).
  6. Fuel Pump Cut-off Switch (Often called "Fuel Pump Resistor" - EFI Models ONLY): Specific to 22RE EFI trucks. Located near the glove box, often taped to the wiring harness behind the passenger side kick panel. Function: During normal engine running conditions, the ECU routes power through this resistor to run the pump at a lower speed. When higher fuel pressure is needed (e.g., cold start, heavy acceleration), the ECU energizes a bypass relay, sending full battery voltage directly to the pump via a separate wire, skipping the resistor. Understanding this is key to troubleshooting "pump works sometimes" issues.
  7. Fuses: Protect the circuit from overloads. Critical fuses include:
    • EFI (15A): Powers the EFI Main Relay, ECU, injectors, sensors (EFI models). Critical for pump relay control.
    • AM2 (30A): High current feed often involved in starter and ignition circuits, feeding power to the EFI Main Relay/Fuel Pump control path.
    • IGN (7.5A): Powers the ignition switch signal circuit, initiating the control path.
    • CB FUEL PUMP (15A - EFI Models): Directly feeds the main power output leg from the EFI Main Relay / Fuel Pump Relay to the pump. Always check this fuse first!
    • Fusible Links: Large, thick wires near the battery positive terminal. Protect main circuits. A blown fusible link for the EFI or ignition circuits will disable the fuel pump. They look like short sections of wire with a plastic connector block and must be visually inspected and tested for continuity. Locate them near the battery positive terminal.
  8. Wiring Harness: Connects all components. Connectors can corrode, wires can break, especially near moving parts (hinges, frame flex points) or after modification. Pay special attention to grounds, often bolted to the engine block, firewall, or inner fenders. A bad ground connection anywhere in the circuit is a common fault.
  9. Fuel Pump: Located inside the tank (Standard Cab) or frame-mounted (Xtracab). Has a 2-pin connector (Power and Ground). Its performance degrades over time.

How the Circuit Works (22RE EFI Models - The Most Complex Scenario)

Understanding the sequence clarifies diagnosis:

  1. Ignition ON: Turning the key to "ON" powers the ECU and sends a signal (likely via the IGN fuse) to the EFI Main Relay. The EFI Main Relay may activate briefly for a few seconds to prime the system, then turn off unless the engine starts.
  2. Engine Cranking: When you turn to "START," several things happen:
    • The starter motor engages.
    • Power flows through the starter circuit to the EFI Main Relay (confirming the "engine cranking/running" signal).
    • The ECU receives a signal (Ne signal from distributor) that the engine is turning.
    • The ECU activates the EFI Main Relay (if not already on) and grounds the Fuel Pump Relay coil (if equipped).
    • This sends main battery power through the EFI fuse/CB FUEL PUMP fuse, through the EFI Main and Fuel Pump relay contacts, and towards the fuel pump.
    • Power is routed through the Fuel Pump Cut-off Resistor, running the pump at low speed.
  3. Engine Running: Once the engine starts, the ECU continues to receive the NE signal, keeping the EFI Main Relay and Fuel Pump Relay energized. The pump runs continuously, typically through the resistor.
  4. High-Speed Mode (Resistor Bypass): When the ECU determines more fuel pressure is required (e.g., cold engine, sudden throttle opening), it energizes the circuit bypassing the resistor. This sends full battery voltage directly to the pump via a different circuit wire, significantly increasing its speed and output. Failure of this bypass circuit can cause drivability issues under load.

(Simplified) Carbureted Models (22R):

While simpler, variations exist. Later carbureted models often incorporated an electric pump and relays similar to EFI, but without ECU control. A common pattern:

  1. Ignition ON/Engine Cranking: Similar path to EFI: Power flows through the EFI Main Relay (or a dedicated Circuit Opening Relay), controlled by ignition switch position and a signal confirming the engine is cranking/running (often taken from the ignition coil negative terminal). This signal might be generated via engine oil pressure (less common on Toyotas, more common on older US vehicles) or via the ignition primary circuit. Power is sent to the pump.
  2. Safety Aspect: The "engine running" signal is critical. If the engine stalls, the pump should stop, preventing a dangerous fuel flood in case of an accident or failure. Lack of this signal prevents the pump from running unless the engine is cranking/running.

Critical Wiring Colors & Connections for Diagnosis

Disclaimer: Wiring colors can fade, be repaired, or vary slightly. Always trace and verify using the circuit logic and your specific truck. Use terminal shape (Male/Female) and connector keying for positive identification. These are common colors for 1990:

  • Power Source to EFI Main Relay: Thick White/Black (W-B) wire from fusible link/battery positive.
  • EFI Main Relay Output (Main Power to Fuel System): Thick Black/Yellow (B-Y) or Black/Red (B-R). This powers the ECU, injectors, and provides the main power source for the fuel pump relay/fuel circuit via the CB FUEL PUMP fuse.
  • EFI Main Relay Control Coil: Switched Power (IGN ON signal) - Often Blue/Red (L-R). Ground Path - ECU controlled or Ignition Signal (for carb models).
  • Fuel Pump Relay (Control Side - Coil):
    • ECU Control Signal (Switched Ground): Brown/Yellow (Br-Y) - ECU grounds this to activate the relay.
    • Power Feed to Coil: Usually powered directly from EFI Main Relay output via a fuse (e.g., 7.5A INJ fuse). Color varies, often White/Red (W-R) or similar.
  • Fuel Pump Relay (Load Side - Contacts):
    • Power Input: Comes from EFI Main Relay output via CB FUEL PUMP fuse (15A). Often Black/Yellow (B-Y) or Black/Red (B-R).
    • Power Output: Runs directly to the fuel pump connector (via the resistor during low speed). Very important wire! Common colors: Black/Red (B-R) or Black/White (B-W). Test Point: This wire should have battery voltage when the relay is activated (engine cranking/running).
  • Fuel Pump Cut-off Resistor Circuit:
    • Input to Resistor: Black/Red (B-R) or Black/White (B-W) from Fuel Pump Relay output.
    • Resistor Output (to Pump during LOW speed): Often Blue or Black/Blue (B-L).
    • Fuel Pump Resistor Bypass Relay (Control): ECU controlled wire. Common color Red/White (R-W) or Yellow/Green (Y-G).
    • Direct HIGH Speed Power to Pump: Activated by the bypass relay when energized. Usually White/Black (W-B) or similar thick wire connected directly to main power.
  • Fuel Pump Ground: Critical! Very commonly Black (B) or Black/Green (B-G). Grounds directly to the vehicle chassis, usually at a point on the frame rail near the pump location (Xtracab) or via the chassis connection of the main wiring harness under the cab/tank. A poor connection here is a frequent cause of failure.
  • Engine Cranking/Running Signal (for EFI Main Relay on carb models): Often originates from the negative (-) terminal of the ignition coil. Look for a wire like Blue/White (L-W) or Blue/Red (L-R) connecting the coil (-) to the EFI Main Relay.

Step-by-Step Diagnosis: Finding the Fault

Follow this logical sequence:

  1. Verify the Pump is the Culprit: Before deep wiring dive, confirm the basics:

    • Listen: Have an assistant turn the key to "ON" (EFI models: listen for a brief 1-2 second prime whine near the pump location). Have them crank the engine – listen carefully for pump operation (hums, whines). Sometimes use a mechanic's stethoscope or long screwdriver pressed against the pump housing/frame, handle to your ear. No sound doesn't automatically mean bad pump!
    • Check Fuel: Is there fuel in the tank? Gauge accuracy isn't guaranteed. Add a few gallons to be sure.
    • Check Fuel Pressure: The most direct test. Rent/buy a gauge. For EFI (22RE), locate the fuel pressure test port on the fuel rail (often looks like a Schrader valve). Connect gauge. Turn key to "ON" (should show prime pressure briefly). Crank engine (should see ~35-42 PSI steady). Low or no pressure points to supply issues (pump, filter, regulator, wiring). For Carb (22R), you might need to disconnect the outlet hose carefully near the pump or carburetor inlet and crank into a container (BE SAFE!). Should see strong spurts. Skipping this step can lead to chasing electrical gremlins for a bad pump or clogged filter.

  2. Check Fuses & Fusible Links: Start simple! Visually inspect and test with a multimeter (set to continuity or Ohms) or test light:

    • EFI Main Fuse (15A - EFI Models): In cab fuse panel.
    • CB FUEL PUMP Fuse (15A - EFI Models): Often in a separate relay/fuse box under the hood or inside the cab (check owner's manual location). Test it.
    • IGN Fuse (7.5A): Powers ignition switch circuits.
    • AM2 Fuse (30A): Key starter/ignition power feed.
    • All Relevant Fusible Links: Located near battery (+) terminal. Visually check for burning/melting. Disconnect battery negative, then test each link end-to-end with a multimeter (should read near 0 Ohms). Replace entire link if blown. Specific links vary, but usually one for EFI/IGN circuits.

  3. Check for Power at the Fuel Pump Connector: Go straight to the source.

    • Locate Pump Connector:
      • Xtracab: Under driver's side (pump frame-mounted). Follow frame rail. Unplug the 2-pin connector (Pump Power & Ground).
      • Standard Cab: Access requires lowering the tank. Often easier to test wiring at the access panel near the tank top or inside cab where harness passes through before final run to the tank. Unplug the connector going to the tank sender/pump.
    • Test with Multimeter:
      • Reconnect battery negative for this test.
      • Set multimeter to DC Volts (~20V range).
      • Back-probe (carefully!) the Power terminal pin on the harness side of the connector (don't damage seals). Connect multimeter Negative lead to a known good ground point (battery negative terminal, clean bolt on engine).
      • Connect multimeter Positive lead to the Power pin you probed.
      • Have assistant turn key to "ON" (EFI models: watch for brief voltage pulse). Then crank the engine. What do you see?
      • Battery Voltage (12V+) Present While Cranking: Circuit up to the connector is working. The pump itself or its ground path is faulty. Proceed to test the pump directly and check its ground.
      • Low or No Voltage Present While Cranking: Problem lies back up the circuit (relays, fuses, wiring, switches, ECU).

  4. Testing the Ground Circuit: Often overlooked!

    • Disconnect the fuel pump connector.
    • Set multimeter to Ohms.
    • Connect one lead to the Ground pin in the harness side connector.
    • Connect the other lead to battery negative terminal or known good clean chassis ground.
    • Should read near 0.0 Ohms. Any resistance over 0.5 Ohms indicates a bad ground connection. Inspect the ground wire path, find where it bolts to chassis, clean connection point (wire brush, sandpaper) to bare metal, resecure bolt. Re-test.

  5. Testing the Fuel Pump Directly: If you have power and good ground at the connector but the pump doesn't run, the pump itself is suspect.

    • CAUTION: Sparks near fuel pump are dangerous! Work outdoors, no ignition sources. Have fire extinguisher ready. Minimize spilled fuel.
    • Disconnect the pump connector.
    • Using jumper wires, connect the pump side connector pins directly to a known good power source and ground:
      • (+) Pump pin to battery Positive terminal. Use appropriate gauge wire for short-term test (fused jumper is ideal).
      • (-) Pump pin to battery Negative terminal or clean chassis ground.
    • If the pump runs strongly, it's good. If it doesn't run, hums weakly, or is noisy, replace it. Note: This confirms electrical function but doesn't guarantee it can create sufficient pressure.

  6. Verifying Relay Operation: (Assuming No/Low Power at Pump Connector).

    • Locate Relays: Find EFI Main Relay and Fuel Pump Relay per locations described earlier (under dash driver side, engine bay fuse box). Identify each by feel (listen for click when key cycled), labels in manual, or tracing wires.
    • The Tap Test: With key in "ON" position, tap each relay firmly with a screwdriver handle. If you hear the pump briefly whir or the relay clicks erratically, the relay itself is likely bad (cold solder joints internally).
    • Swap Test: If you have an identical relay (e.g., the one for headlights, horn, or AC - verify ratings & pinout match!), swap it into the EFI Main or Fuel Pump Relay socket. See if the pump now works. Relays are often interchangeable for testing purposes.
    • Voltage Testing at Relay Socket: Requires multimeter and wiring diagram pinout for your exact relay type.
      • Identify terminals: Coil Control Side (Usually 2 pins: 1 gets switched power, 1 gets control ground) and Contact Side (Usually 3 pins: Common [power input], Normally Open [NO - power output], Normally Closed [NC - rarely used]).
      • With relay REMOVED, test socket:
        • Should have constant Battery Voltage (12V+) on the contact "Common" pin (thick wire). Verify with key OFF.
        • Should have Battery Voltage (12V+) on the coil "power" pin (thinner wire) when key is ON. Refer to diagram.
        • When cranking engine, the coil "ground" pin (thinner wire) should show continuity/voltage drop indicating the control module (ECU or ignition coil signal) is grounding it. Testing voltage here relative to ground when cranking: Should drop to near 0V when activated.

  7. Testing Specific Signals (EFI 22RE Models):

    • Fuel Pump Cut-off Resistor: Check the resistor value with multimeter set to Ohms. Consult manual for spec (often around 0.7 - 0.9 Ohms). Infinite resistance = open, replace. Check connection integrity.
    • Resistor Bypass Relay: Test similarly to main fuel pump relay. Check for power input, control signal from ECU, and output to pump.
    • ECU Signals: Requires deeper diagnostics or scan tool for codes. The ECU relies on signals to activate the relays:
      • Starter Signal: Confirms cranking.
      • IGf Signal (Ignition Fail Signal from Igniter): Essential for confirming spark/run condition.
      • NE Signal (RPM Signal from Distributor): Confirms engine rotation.
      • Check Engine Light (MIL): If it illuminates with key ON (bulb check), goes off, and potentially comes back on if a fault is stored. Retrieve codes if possible. An ECU failing to ground the Fuel Pump Relay control wire is possible but less common than relay/fuse/wiring faults.

Troubleshooting Scenarios

  • Pump Runs Continuously with Key ON: Likely a stuck Fuel Pump Relay or EFI Main Relay. Relay contacts welded closed.
  • Pump Doesn't Run at All:
    • No sound during key ON prime or cranking? Start with fuses (especially CB FUEL PUMP), grounds (pump and chassis), relay check (swap test). Confirm power at pump connector during crank.
    • Sound primes but doesn't run during crank? EFI Models: Check for NE signal, crank sensor (often part of distributor), engine ground straps, ECU power/grounds. May require code scan.
  • Pump Runs Intermittently / Weakly: Suspect bad connection:
    • Wiring Harness: Wiggle test the harness near pump, under dash, at relays while engine is running. Focus on connectors - corrosion or loose pins are common.
    • Connectors: Unplug and inspect pump connector, relays, ECU connectors. Look for green/white corrosion, bent/broken pins. Clean with electrical contact cleaner and reassemble. Apply dielectric grease after cleaning/drying.
    • Fuel Pump Cut-off Resistor Circuit: Faulty resistor, bypass relay, or wiring connecting them. Check resistor value and relay function.
    • Failing Fuel Pump: Deteriorating internals cause slow start or low pressure. Confirm with fuel pressure test.
  • Pump Runs But Engine Still Won't Start: Verify fuel pressure is adequate (test required). Pressure could be too low due to failing pump, clogged fuel filter, leaking fuel pressure regulator, or restricted lines. Also consider non-fuel issues (spark, timing, air intake).

Accessing and Replacing the Fuel Pump

Xtracab (Frame-Mounted):

  1. Disconnect battery negative.
  2. Relieve fuel pressure (EFI models only).
  3. Support vehicle securely on jack stands. Chock wheels.
  4. Locate pump housing on driver's side frame rail below driver's area. Clean surrounding area.
  5. Disconnect wiring harness plug.
  6. Loosen hose clamps on inlet and outlet hoses. Carefully disconnect hoses (expect fuel spill - capture with rags). Identify which is inlet (from tank) and outlet (to engine). Plug or clamp lines if possible.
  7. Remove bolts securing pump housing cover plate or bracket. The pump assembly slides out of the housing.
  8. Remove clamp(s) securing pump within housing.
  9. CAUTION: Note pump orientation. Fuel outlet connection is key. Many frame-mount 1990 pumps look symmetrical but must be installed pointing the correct way. Transfer gasket/seals. Use new seals!
  10. Install new pump assembly into housing, reassemble clamp/bracket, connect hoses/clamps securely.
  11. Connect wiring.
  12. Reconnect battery, turn key ON to prime. Check for leaks thoroughly before starting.

Standard Cab (In-Tank):

  1. Disconnect battery negative.
  2. Relieve fuel pressure (if EFI).
  3. Safely support vehicle high enough for tank removal. Ensure proper support.
  4. Syphon fuel out of the tank as much as possible.
  5. Disconnect filler neck hose, vapor return hoses (if equipped), electrical connector for pump/sender.
  6. Support tank securely (transmission jack preferred).
  7. Remove tank straps carefully. Tank will lower.
  8. Once accessible, disconnect the main fuel line from the pump assembly's hard line connector near the sender access plate. Plug line.
  9. Remove the large ring securing the pump/sender assembly to the tank (might require special tool or large hammer/chisel). Avoid sparking!
  10. Lift entire assembly out carefully. The sock filter is attached. Replace this filter and all seals/gaskets on the sender/pump assembly. Pay close attention to how the float arm is oriented.
  11. Install new pump/sender assembly (use new gasket/seal), secure lock ring.
  12. Connect fuel line, electrical plug.
  13. Carefully reinstall tank, connect filler neck/vapor lines, secure straps.
  14. Reconnect battery, prime, check for leaks obsessively.

Essential Wiring Diagram Information for 1990 Toyota Pickup Fuel Pump Circuits

While a visual diagram is invaluable, understanding the textual description of the paths is crucial:

EFI (22RE) - General Path:

  1. Battery (+) -> FUSIBLE LINK -> Thick W-B wire -> EFI Main Relay Terminal "Power Input" (Contact Side Common Pin - often labelled "BAT" or "C").
  2. Ignition Switch "ON" or "Start" -> IGN Fuse -> Wire (often L-R or similar) -> EFI Main Relay Terminal "Control Power" (Coil Side Power Pin - often labelled "IG" or "+").
  3. ECU (Receiving IGf, NE signals) -> Wire (Br-Y typically) -> Fuel Pump Relay Terminal "Control Ground" (Coil Side Ground Pin - often labelled "E" or "-").
  4. EFI Main Relay Terminal "Power Output" (Contact Side NO Pin - often "FUEL" or "OUT") -> CB FUEL PUMP Fuse (15A) -> Wire (B-Y or B-R) -> Fuel Pump Relay Terminal "Power Input" (Contact Side Common Pin - often "C" or "BAT").
  5. Fuel Pump Relay Terminal "Power Output" (Contact Side NO Pin - often "FP" or "OUT") -> Wire (B-R or B-W) to Fuel Pump Cut-off Resistor Input.
  6. Fuel Pump Cut-off Resistor Output -> Wire (B-L often) to Fuel Pump Connector POWER Pin.
  7. Fuel Pump Connector GROUND Pin -> Wire (B or B-G) -> Chassis Ground Point. Usually bolted nearby.
  8. (Resistor Bypass Path): ECU Control Signal (e.g., Y-G) -> Resistor Bypass Relay Control Coil.
  9. Resistor Bypass Relay Power Input -> Battery Source (e.g., W-B).
  10. Resistor Bypass Relay Power Output -> Wire (often thick W-B or similar) -> Fuel Pump Connector POWER Pin (provides direct voltage, bypassing resistor).

Carbureted (22R - Common Path with Electric Pump):

  1. Battery (+) -> FUSIBLE LINK -> Wire to EFI Main Relay / Circuit Opening Relay "Power Input".
  2. Ignition Switch "ON" or "Start" -> IGN Fuse -> Wire -> Relay "Control Power".
  3. Ignition Coil Negative Signal (Confirms Cranking/Running) -> Wire (often L-W or similar) -> Relay "Control Ground". This signal must be present while cranking or engine running for the relay to close.
  4. Relay "Power Output" -> Fuse (CB FUEL PUMP or equivalent) -> Wire -> Fuel Pump Connector POWER Pin.
  5. Fuel Pump Connector GROUND Pin -> Wire -> Chassis Ground Point.

Conclusion: Methodical Diagnosis is Key

Getting your 1990 Toyota Pickup's fuel pump circuit running again requires identifying your specific Cab and Fuel System configuration, understanding the key components (especially relays and fuses), performing systematic voltage and ground tests at the pump itself and working backwards through the relays and fuses when needed, and applying rigorous safety precautions. While this guide provides detailed textual descriptions based on the 1990 wiring, consulting a visual factory manual wiring diagram specific to your VIN is the ultimate resource for accurate terminal identification and connector views. Don't guess – test with a multimeter. Start with the simple stuff (fuses, grounds, listening) before delving into relays and complex ECU signals. Remember, most problems stem from bad connections, blown fuses, or failed relays, not necessarily the pump itself. Be patient, be safe, and this foundational circuit knowledge will get your Toyota Pickup back on the road.

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