2018 Yaris SE 5MT - T-Sport w/Valvematic!

[atomic_hoji]

Originally Posted by CrankyOldMan

What about swapping the fuel pump itself for one that doesn't use PWM? I'm not sure if the previous gen Yaris uses a fixed rate pump or not, but none of the 2ZR-FE swaps have the same fuel problem.

Mm.. I don't think my Yaris fuel pump is the issue. Looks like all Yaris - older and current - all use fixed ON/OFF fuel pumps. The ECM detects IGN and crank motion, grounds FPC terminal to energize the C/OPN relay and the fuel pump runs - nice and simple. My Google-fu finds the 10th gen. Corolla and xD use this same fuel pump control method, hence why in those swaps the ECMs worked without issue with the Yaris fuel pump setup.

Why I'm running into problems is that 2014+ systems have this fuel pump control ECU that receives the ECM duty cycle output signal and controls power to the fuel pump motor. The ECM must be programmed with injection pulse widths expecting that the fuel pump flow is corresponigly reduced as the ECM is requesting on the FPC output. Where-as my Yaris fuel pump flow is hardwired to run ON/OFF style, so when the ECM is for example set to open the fuel injector for # ms and is requesting 77% fuel pump flow, what is happening is the injectors open for # ms with the fuel pump at 100%; the AFR detects it's way rich and pulls the fuel trim to meet target air:fuel.

Or at least that's how I understand it..

Have a fuel pump control ECU ordered with the associated 6-pin connector. Having to bring it in from the California warehouse he said, so could be a bit to get it across the border and out to me. I'll run thr FPC wire this weekend, I think. And see if my 1.75" exhaust tube comes in tomorrow - the truck's muffler has been broken for months, so I've become kind of used to exhaust noise.. lol

-- Adam