Holley 350 Factory Upgrade Module Wiring/Plumbing Instructions

: June 3, 2024
: Holley

Table of Contents

Holley 350 Factory Upgrade Module Wiring/Plumbing
350 Factory Upgrade Module Wiring/Plumbing Instructions
Inlets & Outlets for Each Module
Pump Flow Chart
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Download This Manual (PDF format)

Holley 350 Factory Upgrade Module Wiring/Plumbing

350 Factory Upgrade Module Wiring/Plumbing Instructions

P/N’s: 12-328, 12-329, 12-330, 12-331, 12-332, 12-333, & 12-334
NOTE : Please read all instructions before proceeding with the installation of your new drop in pump hanger. Failure to follow these instructions may result in poor performance, vehicle damage, personal injury, or death. If these instructions are not fully understood, an installation should not be attempted. In this case, please contact Holley’s tech service department or a qualified mechanic.

For 12-328 – 12-333: Although the Holley module comes with factory wiring connections, it is required that the unit be wired with a fuel pump relay via the instructions below.
For 12-334: Unit can be connected directly to the factory connector. For 89-92 vehicles, fuse needs to be changed from 30A to 20A.
WARNING! FOR 89-92’ VEHICHLES IT IS IMPERATIVE THAT THE FUEL PUMP FUSE BE CHANGED TO 20A . FAILURE TO INSTALL THIS 20A FUSE COULD RESULT IN A PUMP MALFUNCTION AND/OR ELECTRICAL FIRE, RESULTING IN PROPERTY DAMAGE, SERIOUS INJURY, AND/OR DEATH.

WARNING!
USE A MINIMUM OF 12 GAUGE WIRE. BE SURE TO CRIMP OR SOLDER ALL CONNECTORS SECURELY AND CLEAN ANY AREA WHERE GROUND LEADS WILL BE FASTENED. FAILURE TO USE THE MINIMUM WIRE GAUGE COULD RESULT IN PUMP MALFUNCTION AND/OR ELECTRICAL FIRE, RESULTING IN PROPERTY DAMAGE, SERIOUS INJURY, AND/OR DEATH.

Disconnect the cables from the battery.
Mount relay/relays in convenient location away from exhaust heat.
A 20A fuse must be run between the red wire that runs between the battery and the relay harness.
NOTE: Wire colors correspond to Holley P/N 12-753. The 12-753 comes with a 30A fuse. The 20A fuse must be purchased separately.
Plug the fuel pump relay harness into the relay, until it locks into place.
Connect the black wire of the harness to ground.

NOTE: Be sure to route all electrical wires clear of any moving suspension or drivetrain components and any exhaust components! Protect wires from abrasion and road obstructions or debris.

WARNING!
IT IS IMPERATIVE THAT A 20A FUSE BE INSTALLED ON THE WIRE THAT GOES BETWEEN THE RELAY WIRING HARNESS AND THE BATTERY. FAILURE TO INSTALL THIS 20A FUSE COULD RESULT IN A PUMP MALFUNCTION AND/OR ELECTRICAL FIRE, RESULTING IN PROPERTY DAMAGE, SERIOUS INJURY, AND/OR DEATH.

NOTE 1: Be sure to route all electrical wires clear of any moving suspension or drivetrain components and any exhaust components! Protect wires from abrasion and road obstructions or debris.
NOTE 2: It is recommended that the factory pump +12V wire be used to trigger the relay. This will retain any built-in safety fuel cutoffs in the event of an accident or rollover.

Inlets & Outlets for Each Module

P/N	Feed	Return	Extra I/O
12-328	16 x 1.5mm	5/16 Barb	Provisions for EVAP vent and Over Pressure

Relief Valve
12-329| 3/8 Barb| 1/4 Barb| 5/16 Barb Vent, 1/4 Barb to 3/8 Barb Adapter included w/ hose and clamps
12-330| 3/8 Barb| 5/16 Barb| 1/4 Barb Vent, Fill Vent
12-331| 16 x 1.5mm| 14 x 1.5mm| 1/4 Barb Vent, Fill Vent
12-332| 16 x 1.5mm| 14 x 1.5mm| 1/4 Barb Vent, Fill Vent
12-333| 16 x 1.5mm| 14 x 1.5mm| 1/4 Barb Vent, Fill Vent
12-334| 3/8 Q.C.| 5/16 Q.C.| N/A

Recommended Parts to connect to adapt to AN plumbing: