Fuel Issue and help please...

[stang4u2nv]

hey guys hope you are all doing great i'm having a little, well it is not a problem but a little concern, my cr is running a little rich so i decided to check my fuel pressure at idle and i pulled on the vacuum hose and my gauge was reading like 47psi. So i lower it because i have an Adjustable unit from aeromotive and as i'm reaching 40 psi i reconncet the vacuum hose and the needle starts to bounce up and down. So then i said well maybe it is because of the vauum hose, but i go check the idle of the car and i start to hear an up and down pitch from the fuel pump. it is not the regular buzzing sound the pump makes but as soon as i increase pressure at the regulator the pump start to make the regular buzzing sound that all mustang fuel pumps make. But the car runs great at 40 psi so i don't really know why is it doing this, any suggestions?????

 

[stang4u2nv]

noone has any ideas?

 

[Paul]

How did you determine that your car is running rich?

 

[stang4u2nv]

wideband O2

 

[ripper]

The way your fuel pump works is this. The more volts the more it will pump. Your fuel regulator determines volts (or amps I aint sure). By turning it down maybe it has a fluctuating effect on your fuel pump. Test your input to your fuel pump and see if its constant. What fuel pump do you have in there?

 

[Paul]

wideband O2

Okay, then what is your AFR?

You have a stock motor, so it follows that you should probably run stock fuel pressure.

 

[stang4u2nv]

Well i just thought it was something weird but i have now disconnected the vacuum line and reset it to 40 psi and everything is good now.... as for my AFR the car runs pig rich at a 10.0 AFR on my wideband...... at WOT, i'm concerned about the way the car runs after it has warmed up, it starts to richen up a lot and lately it has been running even richer at cruisin speed like 10.3-10.7 AFR and if i downshift it then it will run really lean like a 16.0 AFR and it will buck once during the downshift after it reaches that 16.0 AFR. then it will return to 14.7 at idle. Well I'm just waiting on the arrival of my Tweecer r/t and start to tune it and hopefully eliminate all the egr crap and install my 250 shot of nitrous. then hell will break loose, or maybe my motor will god only knows LOL..

 

[Paul]

Don't you have a 100% stock motor? Those numbers seem really out-of-whack for a stock motor with a stock tune.

 

[stang4u2nv]

i have a pro-m 77 mm calibrated for 24 pounders and i don't know but it runs rich, right now i have autolites 23 gapped at 0.48 and it just keeps running like crap, but if a swap the plugs for some motorcrafts asf32c at an even lower gap like 0.42 the car will run like a champ. but the problem come when i use the nitrous, i can't run motorcrafts asf32c with the nitrous or i'll burn the srtap off of it. so i don't know what to do.....

 

[Paul]

The way your fuel pump works is this. The more volts the more it will pump. Your fuel regulator determines volts (or amps I aint sure). By turning it down maybe it has a fluctuating effect on your fuel pump. Test your input to your fuel pump and see if its constant. What fuel pump do you have in there?

This is actually incorrect. 5.0 Mustangs do not have variable voltage to the fuel pump. Voltage is constant at whatever the operating voltage is for the car at the time. Adjustable fuel pressure regulators change fuel pressure by simply allowing more or less fuel to return to the tank depending on the setting.

Paul.

 

[5litrarag]

Isn't stock pressure supposed to be 39-40 psi with vac. on? That means pull the vac. off again and set it to like 32-33 psi and then put vac. back on. Thats should clean you up a lot.