The Electrical SideFew enthusiasts put much thought into powering up their electric fuel pump, but fumble here and even the best fuel pump will never perform up to its capability. All automotive fuel pumps are designed and tested to operate at maximum efficiency, usually between 13.5 and 14.2 volts DC. Aeromotive publishes a graph for its A2000 drag-race pump that shows roughly a 10 percent drop in flow when voltage drops from 13.5 to 12 volts. Another critical point is that as fuel pressure increases, so does the current load on the pump. Why spend big money for a high-volume pump and cripple it with insufficient electrical power?
If you think of voltage as electrical pressure, you're on the right track. But sufficient current (amperage) is also important. That starts by always using a relay to do the switching as well as using larger, high-quality electrical wire to feed the pump. A pump that runs hot all the time may be suffering from low operating voltage. This runs the pump less efficiently and can cause eventual electrical damage. This also demands high-quality electrical connections that are soldered for less resistance. Perform a quick voltage test on your fuel pump by using a multimeter to compare voltage at the back of the alternator with the engine and pump running to voltage measured at the pump. If there is more than a 1-volt drop between these two points, look for resistance in the circuit. Pay particular attention to the ground circuit. Did you use an equal-sized wire for the ground circuit? Remember that the current load is the same for both sides of the circuit.
Dead Heads vs. Return StyleNo, we're not talking about geriatric hippies stuck on the Grateful Dead. This is about full-flow, or return-style fuel delivery systems. In the old days when all a car crafter had to feed was a 300hp small-block, a mechanical fuel pump and a length of rubber hose was all you needed. But with mega-power, normally aspirated engines,and monster supercharged and nitrous'd powerplants, those old ways just won't cut it anymore. If your engine is making more than 500 hp, it's time for a return-style fuel delivery system.
A dead-head system is defined as any system where fuel makes a one-way trip from the tank to the carburetor. When the fuel level drops in the float bowls, fuel that has been hammering up against the regulator begins to move to refill the bowls. When the float first drops, this initial surge of fuel into the bowl creates a pressure drop until the system recovers as fuel flow continues. Once the floats cut off the flow of fuel, the fuel again begins to hammer against the regulator. As you can see, this requires the fuel column to constantly start and stop in an attempt to feed the engine.