What fuse sizes does the MegaSquirt V3.0 external wiring diagram specify?

The diagram shows 2A fuses for the FIdle solenoid relay and ignition-switched circuits, 5A fuses on several supply lines (including the tach/crank position input), a 10A fuse for the fuel pump circuit, and a 20A fuse on the main relay/battery feed.

How is the fuel pump wired in the MegaSquirt V3.0 diagram?

The fuel pump is powered through an FP Relay (terminals 30, 85, 86, 87) with a 10A fuse in its circuit; the relay is controlled by the MegaSquirt board and fed via the ignition switch/battery circuits.

What sensors connect to the MegaSquirt V3.0 main board?

The diagram shows the Intake Air Temp. Sensor, Coolant Temp. Sensor, Heated Oxygen Sensor, Throttle Position Sensor (5 Vref, Signal, Ground), and a Tach/Crank Position Input that accepts Hall, VR, or Coil-negative signals.

How many injectors are shown and how are they powered?

Four injectors (INJ) are shown, powered through the Main Relay circuit that is fed from the battery via a 20A fuse.

How many pins does the MegaSquirt V3.0 main connector have?

The connector is numbered 1 through 19 on the top row and 20 through 37 on the bottom row, i.e., a 37-pin connector.

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MegaSquirt V3.0 Main Board External Wiring Diagram - Pinout, Relays & Fuses

MegaSquirt V3.0 Main Board External Wiring Diagram (EFI Controller)

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MegaSquirt V3.0 ECU external wiring showing DB37/sensor connector pinout, injectors, fuel pump and idle solenoid relays, CLT/IAT/O2/TPS sensors and fuse ratings.

AI caption April 2007 · Photo 1089 of 1818

This document is the external wiring diagram for the MegaSquirt V3.0 Main Board, an aftermarket electronic fuel injection controller by Bowling and Grippo (©2006). It shows the 37-pin main connector (pins 1–19 on the top row, 20–37 on the bottom row) and the color-coded external wiring from the ECU to all supporting components. Depicted circuits include: a Stepper IAC (idle air control), Intake Air Temperature sensor, Coolant Temperature sensor, Heated Oxygen sensor, Throttle Position Sensor (with 5 Vref, Signal, and Ground leads), a Tach/Crank Position input for Hall, VR, or Coil-negative triggering (with + and – leads and a note '(-) where needed'), four fuel injectors (INJ x4), the fuel pump with its FP relay (terminals 30/85/86/87), a Main Relay (30/85/86/87), a relay for a fast-idle (FIdle) solenoid, an Ignition Module/Output line, the battery, and the ignition switch. Inline fuse ratings are marked throughout: 2A for the FIdle relay and ignition-switched feeds, 5A fuses on several sensor/trigger supply lines, 10A for the fuel pump, and 20A on the main battery feed. The diagram is a general MegaSquirt installation reference rather than a factory Ford schematic, useful for anyone converting a vehicle to MegaSquirt EFI.

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Frequently asked questions

What fuse sizes does the MegaSquirt V3.0 external wiring diagram specify?: The diagram shows 2A fuses for the FIdle solenoid relay and ignition-switched circuits, 5A fuses on several supply lines (including the tach/crank position input), a 10A fuse for the fuel pump circuit, and a 20A fuse on the main relay/battery feed.
How is the fuel pump wired in the MegaSquirt V3.0 diagram?: The fuel pump is powered through an FP Relay (terminals 30, 85, 86, 87) with a 10A fuse in its circuit; the relay is controlled by the MegaSquirt board and fed via the ignition switch/battery circuits.
What sensors connect to the MegaSquirt V3.0 main board?: The diagram shows the Intake Air Temp. Sensor, Coolant Temp. Sensor, Heated Oxygen Sensor, Throttle Position Sensor (5 Vref, Signal, Ground), and a Tach/Crank Position Input that accepts Hall, VR, or Coil-negative signals.
How many injectors are shown and how are they powered?: Four injectors (INJ) are shown, powered through the Main Relay circuit that is fed from the battery via a 20A fuse.
How many pins does the MegaSquirt V3.0 main connector have?: The connector is numbered 1 through 19 on the top row and 20 through 37 on the bottom row, i.e., a 37-pin connector.