Fuel Pump Won't Turn On After Battery/Alternator Upgrade - Relay Pins Swapped

Fuel Systembeginner✓ OP Confirmed

Problem

After upgrading to a Toyota Sequoia 150amp alternator, Braille 15lb battery, and big 3 wiring upgrade (0 gauge), the Walbro 450 fuel pump with 12V relay mod stopped turning on. The car would crank strongly but not start. Jumping the fuel pump directly with 12V power confirmed the pump itself was functional.

Fuel pump does not turn on when crankingCar cranks strongly but will not startJumping fuel pump directly with 12V causes it to run normallyCar starts and runs for ~5 seconds on residual fuel pressure then dies12V present on stock trigger wire when cranking but pump does not activateRelay does not energize the fuel pump despite power being present

Root Cause

During the alternator/battery upgrade work, relay pins 86 (trigger/coil) and 30 (constant power input) were accidentally swapped (crisscrossed), preventing the relay from properly switching power to the fuel pump.

Confidence

High confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted February 2023 on SupraForums.com