slow down a fuel pump

Posted on Feb 4, 2014

You can get booster for fuel pumps to increase their rating, but is it possible to do anything to the wireing of an external pump to get it to flow LESS fuel Reason I ask is I am helping my brother out with an engine swap (admittidly, its not a rotary, or an RX7 for that matter). We have put a 4AGE in his KE35 carolla. The fuel system is a lift pump, surge tank and 500hp feel pump.

slow down a fuel pump
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Factory 4AGE FPR. you could run a restrictive return line back to the tank from before the regulator but thats some macgyver *. or you could trade pumps with someone with something smaller. I have a s5 na pump A note on using resistors - your pump probably pulls around 7 or 8 amps at 12 volts and 40psi. You will end up with very large wattage resistors which are not exactly cheap. you can see in this circuit diagram that, from the factory, the resistor relay is supplied voltage from the circuit opening relay through a lightblue/red wire. The wire branches off into two sections. With the resistor relay off (coil disengaged such as at idle), it passes through the resistor inside the box and comes out one of the light blue wires. When the ECU wants to run the pump in high speed mode, the coil in the relay is engaged by a ground supplied by the Green/Red wire. The current now passes through the path of least resistance, through the other matching pair of light blue/red and light blue wires. Because the wires are two pairs (light blue/red and light blue) of the same colors, you would want to check for resistance across each pair to determine which wires to use. One pair (the two wires you want to use) should have some decent level of resistance because it passes through the internal resistor. I believe the other should be open circuit unless you trigger the relay by supplying power and ground to the black/white and green/red...

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