Where the ECU Gets Power:
The 1986 22RE ECU needs several power sources:
* Battery Voltage (+12V): This is usually a fused, switched power source. This is the main power. Look for a large-gauge wire connected directly or through a relay. Check this wire's continuity all the way to the battery's positive terminal. A blown fuse in this circuit is a very common culprit.
* Ignition Voltage (+12V): This is a switched power source that turns on the ECU when the ignition key is turned on. This power is often used to activate circuits within the ECU itself. This line may be fused separately.
* Ground (-): The ECU also needs a good, solid ground connection to the chassis. A poor ground will prevent the ECU from functioning correctly. Trace the ground wire from the ECU to the engine block, ensuring a clean and tight connection.
Why There's No Injector Pulse:
The lack of injector pulse can stem from several issues, all related to power, grounding, or signals:
1. No Power to the ECU: As mentioned above, check all the ECU power sources (battery voltage and ignition voltage) for continuity and correct voltage. Use a test light or multimeter to verify.
2. Poor Ground: A poor ground is a frequent cause of intermittent or no ECU function. Clean all ground connections related to the ECU and engine block. Consider adding an additional direct ground wire from the ECU case to a clean spot on the engine block.
3. Ignition System Problems: The ECU relies on signals from the crankshaft position sensor (CKP) and camshaft position sensor (CMP) to know when to fire the injectors. If these sensors are faulty or their signals aren't reaching the ECU, you won't get injector pulse. Check these sensors and their wiring.
4. ECU Failure: It's possible the ECU itself is faulty. Although less likely, it's a possibility if all other wiring and sensors check out.
5. Incorrect Wiring: Since this is a swapped engine, this is a highly probable cause. The wiring harness from your '84 might not be compatible with the '86 ECU. Double-check your wiring diagram meticulously. Even a single incorrect wire can prevent the ECU from functioning correctly. This includes the power and ground connections already mentioned.
6. Fuel Pump Relay Issues: While you describe no injector pulse, make sure the fuel pump is getting power. A failed fuel pump relay can sometimes prevent the ECU from sending signals to the injectors as a safety precaution.
Troubleshooting Steps:
1. Check all fuses.
2. Test for power and ground at the ECU.
3. Check the CKP and CMP sensor signals. Use a multimeter or oscilloscope to verify the sensors are generating correct signals.
4. Inspect all wiring connections for corrosion, damage, or loose connections.
5. Carefully compare the wiring diagram of your '84 truck and the '86 22RE to identify any differences and ensure proper connections.
6. Verify that the fuel pump is working (fuel pressure test).
If you're not comfortable working with automotive electronics, it's best to seek help from a qualified mechanic specializing in older Toyotas. Incorrectly troubleshooting electrical systems can lead to further damage. A wiring diagram specific to the 1986 22RE EFI system is crucial for this job. You can find these online through various Toyota repair resources or parts suppliers.
