overloading with fuel or bad o2 sensor?

[ittybittyt25]

Alright, so I installed an EVO VIII pump that i got for free when my buddy upgraded to a Walbro 255. Now I realize that EVO VIII pumps have a dual stage voltage system for their fuel pump for high and low load, but according to RRE ( http://www.roadraceengineering.com/fuelpumpflowrates.htm ) even at the stock 12.5 volts it generally moves between 14 and 30 liters per hour more fuel (depending on load) than the stock pump at the same voltage.

I took it out for a test drive and my o2's were lookin crazy. even at idle it would very very low, ie 0.02, until i gave it some gas and then let it idle it would sweep again from 0.2 to 0.8. Under boost, however, is what is crazy, with the stock fuel pump i would see right around 0.92-0.93 volts on a warm day and about 0.89-.90 volts on a cool/colder day under full wot/boost. Now it sees 0.02-0.01 volts under full load/boost.....is it because that much more fuel is flowing that its loading up the o2 sensor?

one more thing....about 2 days ago i did water injection through the vacuum lines to supposedly "clean" the carbon off the valves, cylinders,crown,combustion chamber. Like an idiot i didn't check my o2's between the time i did that and the time i installed this pump (today)......do u suppose i fouled the o2 sensor with water?

 

[ittybittyt25]

Alright i just went ouside to do some fuel pressure readings....

with vacuum hose on it's about 42 psi (which is actually about the same as it was before the pump install).

with the vacuum hose OFF of the regulator it jumped to about 50 psi

at around ~4.5 psi of boost or so it saw around ~54-54.5 psi of fuel

is this too high?

 

[just_passed_you]

This is under the assumption you're using an adjustable FPR.

You set your fuel pressure with the vacuum line off, it should be @ ~38psi (stock)
when you put the line back on, it should drop down into the 20's at idle. If you rev it or get on it, it should go back up to ~38psi and not any past ~40psi, might get close.

 

[XECLIPZEX]

After installing my turbo my o2 readings started doing the same thing, because when I was bolting on my o2 housing I accidentally hit the alternator and a current ran through my housing and fried my o2 sensor. After logging a couple of days and seeing those low o2 #s I finally replaced my sensor and it fixed everything. It might not be your problem but it would be something to look into.