No Start After Engine Rebuild - Faulty ECM (No Injector Pulse)

Electricalintermediate✓ OP Confirmed

Problem

1991 non-turbo manual Supra would not start after sitting for 10 years following an engine rebuild. The fuel pump would not activate with key on (only when jumping +B and FP terminals), and the engine had no injector pulse despite having spark.

Engine cranks but will not startFuel pump does not activate with key on, only when jumping +B and FP at diagnostic connectorNo power at fuel pump relay with key onTachometer jumping while crankingEngine coughs on brake cleaner confirming spark is presentBoth sides of injector plugs are hot at all times with no switchingNo voltage fluctuation at injector connector while cranking (reads 0 volts across both pins)No injector pulseEngine starts briefly on cold start injector then dies

Root Cause

Faulty ECM (Engine Control Module). The ECM was not providing the ground-side switching signal to the fuel injectors, resulting in no injector pulse. This also explained the fuel pump relay not being energized, as the ECM controls the fuel pump circuit through the circuit opening relay on non-turbo models.

Confidence

Moderate confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted September 2019 on SupraForums.com