nitrous/fuel issue. weird
 

ok here goes, while getting dyno tuned by jeff(mm) we ran into a fuel problem. after my car was tuned we tried some n02 pulls. my afrs looked good without spray (wet zex kit). jeff had to keep backing out of the throttle while spraying.

he showed me what was going on and the afrs looked good but when 6000rpm was reached the fuel would drop off very fast and had to abort the run. we connected a fuel pressure gauge which showed a slight drop but not enough to warrant the issue. i will be replacing the pump jic tho.

the weird thing is it was fine while not spraying but while on the n02 it would keep leaning out. i installed the kit with help from diy threads here and questions to ray at bhr.

any ideas?

thanks jesse

What is a slight drop? Do you have a fuel pressure gauge (please say yes if you are spraying)?

no gauge in the car but hooked one up on the dyno. ill get one before i think about that bottle again. drop iirc was less than 5lbs but only while spraying. mm and shelldude thinks my pump might be goingso im going to swap it but it didnt drop w/o n02

If it fluctuates under load that is not good. What was your fuel level when you were on the dyno? Definitely the the Aermotive fuel line adapter and a proper fuel pressure gauge with peak/hold.

i have the adapter but its not installed yet(got it after the fact). to check it on the dyno we used speed1s snap on gauge. it was right around 60 w/o spray but when sprayed afrs would start to lean out fast on the cobb and the fuel pressure gauge would drop a little at 6000rpm so the run was abborted

60psi and higher should be about right. If it drops much lower then you might have a pump issue. Was your fuel level low when you were doing this?

a little over 1/2 a tank. i also contacted charles for some advice. he gave me some things to look into

thanks 9k

so i installed a fuel pressure gauge and it reads right at about 60psi. i dropped in a new oem fuel pump assembly this weekend and now the gauge reads at 56-57psi. could i have gotten a bad pump? it holds steady but it seems like theres less pressure?

another thing im trying to track down is a weird noise when pressing the gas. after i removed my uim to replace the fuel line with a new one and install the adapter ive noticed this noise. i checked for vaccum leaks but havent had too much time to really check into it and havent driven my car. im concerned about the pump pressure and im trying to figure out this noise too.

Pressure in the high 50's are okay. Every gauge is a tad bit different. Your old pump was probably just fine though. What kind of weird news?

sure but i dont have any with me and my car is at home. anything you want to see specificly?



the old pump i took out had about 75k on it and the new gauge i installed read almost 60psi the brand new oem pump reads 56-57psi.

the noise is hard to describe and only is heard when i press the gas and only under load. im going to check all of my vaccum lines again because i did remove the uim to install a new fuel line when i added the adapter

no2 pics. the feul pressure gauge that reads higher is the old pump and the one that reads lower is the new

pressure:scratchhe

btw charles, when i would arm the system and go wot w/o n02 (tank turned off, lines purged) the pressure would drop 1-2lbs but only for a split second with both pumps.

Which Zex kit do you have? Your NMU looks different. Your setup look fine otherwise and the variation in fuel pressure is fine. Have you tried reprogramming the NMU to see if the noise goes away?

well i got the kit used but its the one bhr recommends. i can confirm later. but the noise has nothing to do when spraying, just when i first apply throttle under load. i think i might have leak somewhere after removing the uim to install a new oem fuel line but could not find one. the noise only showed up after i did this. ill try to get it pulled back apart in a day or two. i can try to reprogram it too

never mind, the NMU looks fine, I just looked at mine, it was just the angle of the pic, I couldn't see the hoses coming from the other side of the NMU.

Mine:

http://www.flickr.com/photos/9krpmrx8/5045690968/

so you think the pressure of the new pump and the split second drop when using the system is ok? i hope i didnt pay for a new pump i didnt need and it pisses me off that prussure is ~2lbs lower. i need to find where this leak/wierd sound is. i took a vid this am but i dont know how to get it here. its faint but you can hear it at the end of the vid

I think the pressure drop is fine. You probably did not NEED a new pump but having a new pump is a good thing.

yhea i just wish the new one had the 60 reading of the old

Yeah don't worry about it, just set your alarm function to 50psi and if it drops below that then worry.

so above 50 and im good? thanks 9k and charles. you set my mind at ease

thanks charles. the k&n v2 does have one screen in it

Acceptable fuel pressure per the FSM is 54.4-65.2 psi.