Some questions about the fuel pump

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Some questions about the fuel pump

Postby lalojamesliz1 » Wed May 29, 2019 5:12 am

My afr's lean out sometimes during idle to like 16.0+ and during wot to high 11's to mid 12's and I'm pushing 15-17 psi.
I'm now thinking about replacing my fuel pump with a supra pump.
Is is true I'll run richer during normal driving since it outputs more than the stock pump? I'm not trying to waste more gas during normal driving since I like to drive my all-trac as my daily driver. Anyone know about this or any other issues?
I read already about upgrading the wiring.



NEVERMIND guys.... I'll just get a denso replacement from rockauto.
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Re: Some questions about the fuel pump

Postby underscore » Wed May 29, 2019 7:34 pm

From my understanding the pressure regulator should flow the extra fuel back to the pump. Have you changed the fuel filter recently? Are you still running the fuel pump resistor or is it bypassed?
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Re: Some questions about the fuel pump

Postby lalojamesliz1 » Wed May 29, 2019 7:49 pm

underscore wrote:From my understanding the pressure regulator should flow the extra fuel back to the pump. Have you changed the fuel filter recently? Are you still running the fuel pump resistor or is it bypassed?


I changed the fuel filter a year and a half ago (WIX brand) and I've put about 3k miles. I always avoid cheap gas too. Yes I'm running the resistor.
It's cool buddy, I ordered the stock denso pump last night after reading some threads with people saying it ran richer.
Last edited by lalojamesliz1 on Mon Jun 03, 2019 7:11 pm, edited 1 time in total.
91 Celica all-trac gen3 swap (small-med $$$ sponge)
69 mustang 408w (large $$$ sponge)
08 sequoia 5.7L
14 avalon
02 taco dbl cab V6 turd
and a 2 car garage :shoots:
lalojamesliz1
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Location: Bakersfield, CA

Re: Some questions about the fuel pump

Postby sefiroxx » Mon Jun 03, 2019 4:34 pm

Fuel pump may send various pressures, which are compensated for by the pressure regulatory. The pressure variances remaining are then compensated for by the ECU with measurements from the o2 sensor (too rich, reduce injector pulse width)
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Re: Some questions about the fuel pump

Postby lalojamesliz1 » Mon Jun 03, 2019 7:18 pm

sefiroxx wrote:Fuel pump may send various pressures, which are compensated for by the pressure regulatory. The pressure variances remaining are then compensated for by the ECU with measurements from the o2 sensor (too rich, reduce injector pulse width)


Correct but my afr's should be super rich at WOT. I've noticed it's getting leaner more and more at WOT as time goes by. My car has 156k miles anyways. I don't know how long the pump lasts on average but I know it varies
I replaced the fuel pump on my 08 Toyota sequoia because it was making strange noise while idling after being driven for a little while and it had 115k miles.
91 Celica all-trac gen3 swap (small-med $$$ sponge)
69 mustang 408w (large $$$ sponge)
08 sequoia 5.7L
14 avalon
02 taco dbl cab V6 turd
and a 2 car garage :shoots:
lalojamesliz1
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Posts: 393
Joined: Sun Jul 23, 2017 3:03 pm
Location: Bakersfield, CA

Re: Some questions about the fuel pump

Postby JRWperformance » Tue Jun 25, 2019 12:58 am

My st165 did this after my 4th gen swap. My wideband showed it getting leaner than ideal... I threw in a Denso Supra Turbo pump and this solved the lean out issue. Mine stays in the 11s under full load.
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1988 Toyota Celica

Re: Some questions about the fuel pump

Postby Magroo » Tue Jun 25, 2019 8:24 pm

Before you buy anything I would consider checking to make sure your fuel pump relay is working properly. I believe it's what's called a single pole double throw or spdt relay. In they normally closed position it sends voltage through the resistor so the fuel pump is in a low output state. The ECU triggers the relay to bypass the resistor so the fuel pump is in a high output state.

It's a yellow relay located near the radiator in the passenger side front engine compartment. I think it's grouped with the horn and AC clutch relays.
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