Some questions about the fuel pump

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lalojamesliz1

New member
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.
 
underscore

underscore

Well-known member
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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lalojamesliz1

New member
underscore":ily8fwn2 said:
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?
Click to expand...

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.
 
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sefiroxx

New member
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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lalojamesliz1

New member
sefiroxx":in72b1x7 said:
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)
Click to expand...

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.
 
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JRWperformance

Member
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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Magroo

New member
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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