7 Steps to Fuel Pump Care

FUEL PUMPS: HOW TO AVOID THE BLUNDERS THAT DESTROY THEM
Text & Images by Sam Moore

Today's most popular flow-through-style fuel pumps for performance vehicles are designed to support up to 750 horsepower. Though equipped with close-tolerance Gerotor-style gears (eccentric gears--one operating inside another like that of an oil pump) and an electric motor that's rated for continuous-duty, flow-through-style fuel pumps need to be installed and operated correctly to be reliable. To become thoroughly acquainted with their needs, here are the vital clues to keep your "Flow-through" pumping.

1- Flow-through-style fuel pumps are designed for use with unleaded and leaded gasoline. They cannot function with methanol.

2- Although the electric motor is cooled by fuel flowing around it, installing a heat sink in the system is advantageous because it dissipates heat. An 8" heat sink can reduce fuel temperatures by up to 90-degrees Fahrenheit. Consequently, fuel that's delivered to the engine is cooler and the pump is protected from the higher temperatures.

3- Always mount the pump close to the fuel tank or fuel cell on a solid frame member and position it level with or below the tank outlet. Never mount the pump in the driver's compartment or near moving parts or close to the exhaust or a rear differential. Do not allow the pump motor housing to make contact with any metal component of the vehicle.

4- From the fuel pump to the fuel cell or tank, use a minimum of -10 AN (5/8" bore) fuel hose. Connecting this hose to the existing fuel tank or cell may require rework: involving either the installation of a bulkhead fitting in the fuel tank to connect to the -10 hose or, better, the installation of a welded-in fuel tank sump complete with fittings. From the fuel pump to the EFI Bypass (fuel pressure regulator), use -8 (1/2" bore) fuel hose. Install a -6 (3/8" bore) return hose from the EFI Bypass to the fuel tank/cell. The internal fuel-return pipe (inside the fuel tank or cell) must also be of -6 dimensions and terminate at the bottom of the fuel cell in the front region of the tank. Under no circumstances should returning fuel be discharged above the fuel level. Discharging pressurized fuel into the cell above the fuel level will aerate the fuel and damage the pump. The openings of the 3/8" bore return pipe (inlet) and the 5/8" bore supply pipe (outlet), both of which reside inside the tank, should be positioned as far apart as possible to prevent aerated, hot fuel from entering the supply line. To vent the fuel tank or cell to atmosphere, use a -8 hose or equivalent with a minimum bore of 1/2". Install a small vent filter on the vent hose and terminate it such that it can neither become blocked with debris nor open to the ingress of water. Failure to adequately vent the fuel system will damage the pump. Route the fuel hoses such that they avoid all heat sources including the exhaust and rear differential.

5- A fuel pump, in common with other electrical accessories, performs best when provided with adequate voltage. Use 12-gauge wire to connect the battery to the relay; the relay to the pump, incorporating a fuse in the circuit to protect the pump from overload; and from the pump to ground. The pump MUST be grounded to a good chassis connection with a minimum of 12-gauge wire. Use an 18-gauge wire to activate the relay. All wiring circuits must be fused. Before making electrical connections, disconnect the battery.

6- When installing a new flow-through-style pump, fill the fuel tank and ensure that fuel is present at the inlet port of the pump before attempting to operate it. If the pump does not deliver fuel within 20 seconds, STOP and prime it: operating the pump in a dry condition will damage it. Before driving the vehicle, check the fuel pressure at the regulator with the engine running. Employ a dampened non-liquid-filled gauge. Liquid-filled gauges are affected by heat; consequently, their readings can be unreliable. Make certain that all fuel system components are leak-free before using your system.

7- Maintain the system by checking the fuel filter periodically. Also, check the braided steel lines occasionally by squeezing them with your hands as they can deteriorate from the inside. Checking fuel lines for soft spots can often identify internal degradation before lack of flow or pressure or the presence of debris in the system spells trouble.

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