Electric fuel pump delivery

[Alexis]

When a eletric fuel pump is on what stops it from over pressuring the line if no fuel is being used by the motor? So lets say i just turn on the pump by itself.

Alex

[chickenwing]

Good question. I wanna know too! I expected a bypass line from the pump back to the tank. While flipping through my Summit catalog, I discovered some are set up this way. Maybe a pressure relief valve built into the pump? Pressure rises to rated and offseats a spring load valve feeding fuel back to the inlet? Things that make you go hmmm.

[68LSS1]

Most fuel injected systems these days are of the returnless type and have the pump in the tank (to keep it cool and to reduce noise). These pumps usually incorporate a check valve and relief valve. They are also fixed displacement , meaning the deliver a certain amount (read volume) of fuel for every revolution. Important to note that the more voltage to the pump the more fuel the pump can deliver (see Kenne Bell Boost a Pump and Aeromotive has a controller also). The fuel pump delivers the volume and the lines, filters, injectors, etc create the pressure which is prevented from going past a certain point by the relief valve. Since this valve is part of the pump which is in the tank, it (excess fuel) basically just gets dumped back into the tank. Therefore the pump can keep providing the same volume (pumps are usually rate in gallons/liters per hour.
The other type does utilize a return line and also incorporates a regulator. The regulator is responsible for "venting" excess pressure back to the tank via a return line. The pump has no relief valve and just keeps pumping the same amount (volume). One thing to be careful on this type of system is that you don't cycle the fuel and heat it causing vapor lock issues like quit a few of the cars on the Power Tour this year had. A stock system will not see this, I'm talking a aftermarket system (read big pump) here.
I will be using a Aeromotive A1000 pump with a -10 (5/8") feed line and filters to a Y manifold, through aftermarket fuel logs to the regulator and a -8 (1/2) return line. I will also be using their controller which varies the voltage to the pump by engine RPM to prevent this fuel cycling I mentioned earlier. And on a side note the LS1's require 58psi for the injectors.

[willow72]

i have a edelbrock eletric fuel pump for a carb on my truck with no regulator no return line and the installation directions said i dont need any and i dont use any and i dont understand how it works but have not had any problems yet

[jakeslim]

Originally Posted by willow72

i have a edelbrock eletric fuel pump for a carb on my truck with no regulator no return line and the installation directions said i dont need any and i dont use any and i dont understand how it works but have not had any problems yet

i run the same type of setup. The way it works is the pump is only capable of hitting its max pressure(preset at factory) and once it builds up to that pressure, it will stop or ease up. When I turn my key(but not start), i can hear my pump kick in and build up the fuel pressure to the carb, after a couple of seconds, its stops because it has hit max pressure.
One thing with a carb setup is to make sure the carb is capable of "holding" back the pressure when not running to avoid flooding. I was running with a qjet and was having some leak issues until i bought a fuel pressure regulator. I keep it set at about 5.5 psi