Can I install a Walbro 255lph fuel pump without a tune?
I have a wideband in my car
Just so you know.. My AFR's were 12.2 maxed out on stock pump. INstalled the 255 and went off the chart rich black smoke rolling from the exhaust and car felt like it was chained down..
about 3 pulls later after remaping and fuel was almost dialed in.. went from 8.7's to 10.0's @ WOT. big change.
It will increase fuel pressure 5-7 psi from what i understand.
Just so you know.. My AFR's were 12.2 maxed out on stock pump. INstalled the 255 and went off the chart rich black smoke rolling from the exhaust and car felt like it was chained down..
about 3 pulls later after remaping and fuel was almost dialed in.. went from 8.7's to 10.0's @ WOT. big change.
It will increase fuel pressure 5-7 psi from what i understand.
just so people don't take this one the wrong way, onrails has a evo 8, and the OP has an evo 9. the fuel pumps in the 9 flow more then the pumps in the 8's. with basic bolt ons, you wont see the drastic difference in the 9 before and after the pump like onrails experienced.
I installed the fuel pump on my evo 9 a few days before the AMS tune. It does make your car run (more) rich, the lowest I got on my wideband was 9.X, most of the time 10's at WOT. It also got richer even at partial throttle, dipping down moreso than before it was installed.
It wasn't a huge deal--there wasn't any black smoke (that I could see anyway) and to me the car was running rich even without the pump, considering the soot and color of my bumper, condition of my 02 sensors and wideband, etc.
After the tune she's lighter, and stays in the 14.7-15.00 range for the most part--until I go WOT where she drops to around 10 on the wideband again.
Long story short--you don't HAVE to get the tune right away--but you should if possible.
Also--it's not really necessary for the walbro until you start getting into more major stuff on the car. My next step is going to be cams, UICP/SBK, and some bits here and there...so I decided I might as well do it now since I was getting tune too.
It wasn't a huge deal--there wasn't any black smoke (that I could see anyway) and to me the car was running rich even without the pump, considering the soot and color of my bumper, condition of my 02 sensors and wideband, etc.
After the tune she's lighter, and stays in the 14.7-15.00 range for the most part--until I go WOT where she drops to around 10 on the wideband again.
Long story short--you don't HAVE to get the tune right away--but you should if possible.
Also--it's not really necessary for the walbro until you start getting into more major stuff on the car. My next step is going to be cams, UICP/SBK, and some bits here and there...so I decided I might as well do it now since I was getting tune too.
Thread Starter
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Joined: Mar 2007
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From: Virginia
thanks for all the great info guys. I think im just going to wait till the tune in a few weeks to install it though. I agree that it is not "necessary" for just minor bolt ons, but I dont want to hit 100% duty cycle wich I have seen on the forums before. I think you can get the pump alone for like $79 dollars shipped through one of the vendors. (not sure since I bought more than just the pump with my order?) Small price to pay for a little extra safety though! This is only my first wave of mods, and the second will not be too far off, so I "will need" this pump soon! 
I would go ahead and get the kit. It will replace the gasket and spacer for the pump in the assembly, and also provide you with a new fuel filter and rubber base.
It will take you 30 minutes if you are familiar and have all the tools, and perhaps and hour or so if you want to take your time and be extra careful. Make sure you run your fuel tank to a quarter tank (or preferably less).
It will take you 30 minutes if you are familiar and have all the tools, and perhaps and hour or so if you want to take your time and be extra careful. Make sure you run your fuel tank to a quarter tank (or preferably less).
Thread Starter
Newbie
Joined: Mar 2007
Posts: 77
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From: Virginia
Kit is on its way also 
thanks for the heads up on the quarter tank though!! I had not even thought of that! Never installed one before, but it can be too hard!? Any other words of advice on the install?
thanks for the heads up on the quarter tank though!! I had not even thought of that! Never installed one before, but it can be too hard!? Any other words of advice on the install?
There's an installation VFAQ available that will lead you through the whole process. It's not a big deal.
As long as your fuel pressure regulator and bypass/return lines are working properly, there should be no difference at all in running a larger pump, except when your stock pump is unable to provide adequate fuel under conditions where you are running more air mass than the stock pump is able to match with fuel. Why? Because the fuel pressure regulator controls the fuel pressure (not the ECU), and excess fuel is bled back through the return line to keep the pressure where it's supposed to be.
As long as your fuel pressure regulator and bypass/return lines are working properly, there should be no difference at all in running a larger pump, except when your stock pump is unable to provide adequate fuel under conditions where you are running more air mass than the stock pump is able to match with fuel. Why? Because the fuel pressure regulator controls the fuel pressure (not the ECU), and excess fuel is bled back through the return line to keep the pressure where it's supposed to be.
I just installed the Walbro 255 on my 05 evo 8. Now I can only get up to about 3k rpm, and boost makes it to almost 5psi before it starts to buck. It kind of feels like bad spark plugs. I know the 8's pump wasnt as good as the 9's so is the 225 enough to throw it off like that? As of now, I have an Intake, TBE, and IC pipes. Any help is much appriciated! Thanks!
