I'm working on creating a fuel injection system for my go-kart. It currently has three basic systems that need power: the fuel injectors, the Arduino nano's, and the fuel pump. Right now I have the fuel injectors and Arduino nano's sharing a 12 volt 5 amp power supply and the fuel pump running off of a car battery charger that is rated for up to 100 amps. In this configuration everything is functional. However, I would like it to be able to run off of the 10 amps that the engine supplies so that I don't have to be plugged into a wall to run the go kart. The problem is that the fuel pump will draw all 10 of those amps and the other two systems won't run (my Arduino will shut off). Can someone help me come up with a solution? So far I have researched current controllers and DC motor controllers. Overall I am confused if those limit the current or just limit the speed of the motor. Either way, is their a circuit I could use or a current controller of sorts that will solve my problem?
Thanks for reading and if you have any questions I will respond ASAP.
You're going to need to give some more info. I don't know much about go-karts but I know a bit about cars.
I take it its a carbed kart that youre converting to EFI?
I'm assuming the engine has an alternator, how do you know that its only capable of 10amps?
Run the Arduino from a separate battery.
It is rated at 120 watt alternator (http://www.vintagesnow.com/Polaris_files/85%20engine%20electrical.pdf 1987 polaris sport). The rectifier/regulator converts the alternator output to ~12 volts dc so I assumed that it would be able to supply a maximum of 10 amps.
The battery sounds like a good idea but if the alternator can't charge it because all of the power is going to the fuel pump, the battery will need to be recharged every so often. I would prefer to avoid that. This brings me back to wanting a way to limit the current that the fuel pump consumes.
Can you link the fuel pump youre using?
I'm assuming you're designing a port injection system? 10amps seems like a lot
Hi,
The problem is that the fuel pump will draw all 10 of those amps and the other two systems won't run (my Arduino will shut off).
Can you please post a circuit diagram that this happens, or are you surmising that this may happen?
Tom... 
You already know the problem with your solution. How far can you reduce the fuel pump speed and still get the fuel pressure you need?
Paul
The problem is that the fuel pump will draw all 10 of those amps
Seriously? 120W to pump fuel? I don't believe it, have you measured the current taken by the pump during normal operation?