So I have been thinking about replacing my OEM fuel pump with a Supra pump or something that is a bolt in to enhance the reliability of my car. I have read that the current draw of the Supra pump may be too high for the stock wiring and relay system, particularly the low speed system that reduces voltage.

I can easily rewire the fuel pump to use battery voltage and just use the OEM circuit to trigger a new relay, but then the system will be at 13-14v all the time. What I am wondering is what impact this will have on fuel pressure at low speeds and resulting AFR’s, when the FP would normally be lower due to the voltage reduction system. Because I live in California, I need to be able to run my car with the stock ECM every so often for smog check – so I need a solution that allows this.

I have read a few posts that seem to talk about the AFR getting richer at low speeds with the fuel pump wiring mod, which indicates that the fuel pressure regulator is not capable of maintaining proper pressure with the mod. But, I have not found any detail information on this. I would like to beef up my fuel system though…

So the questions are:

If the fuel pump wiring mod is done, does fuel pressure stay correct or is re-tuning needed?

The Supra pump current draw seems to be too much for the stock wiring system, so is there an upgraded pump that is a bolt in that would provide some additional headroom and work within the stock wiring system?

Any firsthand knowledge on this would be greatly appreciated!

 

I don't have any numbers for scientifical evidence, but my car ran better with just a fuel pump re-wire and it simplifies the system. I only have a full exhaust system, simplified sequential twins, and an hks hot air intake. It ran great on the stock ecu when I had the car together. If you are going for bigger power, then I would recommend a bigger pump and a rewire for safety and reliability.