Inspect and make the system safe
- Follow fuel-system safety procedures and inspect the tank, lines, filter, regulator arrangement and engine bay for leakage, restriction or incorrect routing.
Technical Training Module 22
EFI: Fuel Delivery & Injection Control
EFI: Fuel Delivery & Injection Control for EFI fuel supply, injector control, air measurement, closed-loop trim, and correct diagnostic order.
voltagecurrentresistancegroundrelaysolenoidsensorECU
How The System Works
The fuel-delivery system uses a pump, relay or control module, filter and regulator arrangement to supply fuel under the conditions defined by the donor design. The injectors normally share a power source, while the ECU controls each injection event. Delivered fuel depends on supply pressure, injector condition and ECU command, not injector pulse alone.
A swap must preserve the correct pump-control logic, wiring capacity, grounds and regulator or return-system arrangement. A no-start, lean condition, rich condition or cylinder misfire can result from lost pump command, voltage drop, inadequate volume, incorrect pressure, leakage or an injector electrical or mechanical fault.
Step By Step Test Procedure
Confirm ECU enable conditions
- Record codes and confirm cranking-speed and authorization information before treating a missing fuel command as a pump fault.
Measure delivery
- Test fuel pressure and volume at the approved point against the exact donor procedure during prime, cranking, running and load as applicable.
Load-test pump wiring
- Measure pump-feed and ground voltage drop while operating and verify the relay or control circuit under load.
Prove injector control
- Verify common feed and ECU pulse with an approved noid light, oscilloscope or current probe; isolate the circuit before resistance or short testing.
Check balance and leakage
- Where supported, perform injector balance or leakage checks, repair the identified fault, confirm no leaks and repeat pressure, running and scan-data checks.
Expected Readings And What They Mean
| Check | Expected Evidence | Diagnostic Meaning |
|---|---|---|
| Pump control and loaded supply | Pump command, feed and ground are present under the conditions defined by the donor system | Command without proper loaded voltage indicates relay, wiring, connector or ground resistance. |
| Fuel pressure and delivery volume | Pressure and volume meet the exact engine and regulator specification during the required tests | Correct static pressure with inadequate volume can still cause lean operation under load. |
| Pressure retention or leakage | Residual pressure behaviour follows the donor service procedure after shutdown | Excessive loss can indicate pump check-valve, regulator, injector or external leakage. |
| Injector feed, pulse and contribution | Common feed is present, ECU pulses are consistent and cylinder contribution meets the specified test method | Missing common feed affects all injectors; an individual electrical or flow fault isolates one cylinder. |
Use This Carefully
This training page is an independent Lexus V8 Engines LLC rewrite for educational and diagnostic support. Lexus V8 Engines LLC is not affiliated with or endorsed by Toyota Motor Corporation. Always use the correct factory service information for final specifications, safety procedures, and vehicle-specific wiring.