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Fuel Pump Dying - walbro 255 to 450. Does upgrading require a retune?

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Fuel Pump is starting to whine on my s15 jdm.

 

I have a 255 walbro pump on e85. If i go to 450 walbro on e85, does it need a retune? I am running stock fuel pressure regulator. Heard its okay as long as you have a fuel pressure regulator, but since mine is stock I am not sure.

Thanks to anyone who can help.

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I would get the AFR's checked.

I would also run a relay with 12v batt power to walbro 460lph e85 pump as well.

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the question was, sorry if it sounds rude, but would i require a retune if i simply go from a 255 to 450 lph fuel pump? Thank you.

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How so if FPR is keeping pressure to injectors the same?

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There is potential that the stock FPR might not be able to bypass enough of the fuel to keep pressure low enough at say idle and cruise.

 

 

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Running walbro 460 with stock reg no issues.

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what a load of crap, if u got a reg, ur pressure will stay the same, i just went from stock intank pump to a walbro 460, and a holley dominator 1800 external pump and i even changed from a tomei type L pressure reg to a holley one and it was exactly the same afr wise, i have an afr gauge by the way which is hardwired in.

Edited by DRE20

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what a load of crap, if u got a reg, ur pressure will stay the same, i just went from stock intank pump to a walbro 460, and a holley dominator 1800 external pump and i even changed from a tomei type L pressure reg to a holley one and it was exactly the same afr wise, i have an afr gauge by the way which is hardwired in.

 

This. That is all.

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So why'd my base fuel pressure jump 1 bar when I hard wired my 460lph and ran a -6 feed line all the way to the FPR? that's on a TURBOSMART fpr1200 v2 which flows heaps.

 

If the FPR cannot bypass enough fuel, pressure will raise.

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the question was, sorry if it sounds rude, but would i require a retune if i simply go from a 255 to 450 lph fuel pump? Thank you.

 

only if your car was tuned on a faulty pump then yes.. however if the base pressure & fuel pressure throughout the run was the same on both pumps then no.

 

Do you have a wideband? if it's running pig rich then you'll need a touch up on the fuel table.. nothing big.. easy enough to knock back in 15~20 minutes on a dyno.

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I have a holley dominator 1800 fuel pump and the AFRs are unchanged between both, because the fuel pressure regulator REGULATES the fuel pressure :P

 

People who say "it won't be able to bypass that much fuel" have no idea what they're talking about :P

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Oh, my FPR must be different to all the other FPRs. That must explain why my base pressure increased when more fuel was being squeezed through it at higher pressure.... Definitely not normal by the sounds of it. Thanks for clearing that up.

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Oh, my FPR must be different to all the other FPRs. That must explain why my base pressure increased when more fuel was being squeezed through it at higher pressure.... Definitely not normal by the sounds of it. Thanks for clearing that up.

 

sounds fishy to me bro, how did u fix the problem anyways? Full retune or did u adjust the pressure by adjusting the actual fuel pressure regulator?

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Oh, my FPR must be different to all the other FPRs. That must explain why my base pressure increased when more fuel was being squeezed through it at higher pressure.... Definitely not normal by the sounds of it. Thanks for clearing that up.

 

If the rail pressure increased with a higher flowing pump then your FPR is broken. The FPR has a spring and dampener assembly that regulates rail pressure mechanically. It opens and closes the bypass valve as needed to keep the fuel rail at constant pressure. The stock FPR is capable of flowing pretty huge amounts - at max opening it is no more restrictive than a bent tube and the return lines are the same size as the feed lines.

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I fixed it by adjusting the the base pressure.

 

The FPR itself doesn't know what pressure its aiming for and doesn't actively correct it like an o2 sensor would correct AFRs. You set the base pressure to whatever you want (say 43.5psi) and it adds or subtracts 1psi of fuel pressure relative to air pressure. So the FPR doesn't know to open more to vent extra fuel flow from a bigger pump to maintain 43.5psi it just opens based on the tension of the valve.

 

But maybe I'm missing something

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Yeah you are, pretty much the reg is a valve controlled by a spring, when pressure on one side of the valve gets high enough it compressors the spring to allow the valve to open and fuel to flow out, if this wasn't the case you would get a massive drop in fuel pressure at high revs because of the lack of flow as the injectors are putting it all threw the motor. The change in pressure from the boost/vac port is from a diaphragm that uses air pressure to add or subtract tension on the spring. If changing a fuel pump effected fuel pressure either the reg is faulty or you have an issue down stream of the reg like a kinked return line.

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It's called a regulator for a reason.

 

If you've changed pumps and there was a massive increase in pressure one plausible reason could be your old pump was so fuuuccked you pretty much had the FPR tensioned all the way down to the point it was pretty much shut (I.e. Spring holding diaphragm fully compressed down) so when a new pump was introduced the FPR was closed all the way and unable to regulate the fuel.

 

That's the only reason I can think of, unless you've got a china reg with a china gauge which reads in dim sims and not psi or bar.

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It's called a regulator for a reason.

 

If you've changed pumps and there was a massive increase in pressure one plausible reason could be your old pump was so fuuuccked you pretty much had the FPR tensioned all the way down to the point it was pretty much shut (I.e. Spring holding diaphragm fully compressed down) so when a new pump was introduced the FPR was closed all the way and unable to regulate the fuel.

 

That's the only reason I can think of, unless you've got a china reg with a china gauge which reads in dim sims and not psi or bar.

 

Indeed.

 

I wouldn't be wasting money retuning. Nor should you bother with a relay if your 255 did the job with the power you're making on e85. The 460 only needs extra juice beyond 320rwkw

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Uh, the gauge and FPR are genuine Turbosmart so readings were in centrelink cheques. #sponsoredbycentrelink

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Uh, the gauge and FPR are genuine Turbosmart so readings were in centrelink cheques. #sponsoredbycentrelink

 

fuark, my taxes are funding your car.. *4sshole* lol

Edited by Johnnilicte

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Uh, the gauge and FPR are genuine Turbosmart so readings were in centrelink cheques. #sponsoredbycentrelink

 

 

fuark, my taxes are funding your car..

 

*4sshole* lol

 

That's it, tax avoidance scheme is in full effect. Lol :)

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Fuel pressure regulators are pretty simple, and there is only so much that a spring can do. They work pretty well for such a simple reliable mechanical device, but they are not a highly accurate device. The outlet pressure is influenced slightly by changes to the inlet pressure and the fuel flow demand.

 

The affect of a pump change may be greater if the in-tank pressure relief valve has been removed. I think that the valve ensures the pressure to the FPR inlet is more or less constant. Although that is a guess as I don't know what pressure it opens at, and most pumps also have a built-in pressure relief valve.

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Hey don't underestimate the good old FPR. It may be simple, but with a working vac line they're really quite accurate. Really impressive for a cheapo device on a 20 year old car! Compare them to coilpacks that regularly fail - they're a simple electrical device (even simpler than an FPR) but they pack it in all the time... Gotta remember that the fluid and air pressure found on a common car are tiny compared to the strength of the materials used in the components.

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