and another great and pretty much needed item for boosted vehicles. Great/fantastic troubleshooting device in it's own right. I know spending more money sucks, but...seeing where your vehicle's fueling is in reality is waaaaay better than fuel psi. Granted fuel psi is a pre-cursor to a problem.

 

Originally Posted by krambo
Have it on a wide band yet?

I had a mechanical gauge hooked on the fuel rail and up under the windshield wiper. I don't know to much about wide bands, I know there is a wideband for your Air/fuel ratio, is this what your talking about, I plan on getting one soon.
Mark

 

I was following the previous thread because I have a similar problem. Mine sits @ 50psi at idle. It does shoot up to 60 (give or take -2psi) at WOT but as soon as I get off the throttle it drops like a rock into the low to mid 40's and the sloooooowly builds back up to 50 while I'm coasting along.

A wideband would be the best indicator to see if you're running lean or not. I would also, definitely get a mechanical pressure gauge and check it.
You've already replaced:
FPR
Fuel filter
Made sure the inline pump is grounded well and functioning? ( I can hear mine humming when I'm at a red light)
Are your O2 readings where they should be? Just thinking out loud here...could it be so rich at WOT that there is nothing wrong your fuel delivery system, it just cant keep up. Maybe because the AFR is so rich the injectors are just firing off more fuel than the system can get into the fuel rail? I haven't had my AFR checked since the 6L swap. I'm hoping this is part of my problem...just too damn rich.

 

Your truck has the return fuel system with the vacuum/boost operated fuel pressure regulator (FPR). That is how that system is supposed to operate. At idle you should see around 50 - 53 psi. At medium throttle it will build to 55 - 60 psi. At WOT under boost you should see 62+ psi. Under deceleration ( when you lift completely off the throttle) the engine builds higher vacuum and your fuel pressure will drop below 50 psi for a little while. The FPR is on the drivers side of the fuel rail on a stock engine and should be close by on the radix. It has a vacuum/boost line going to a port on the radix. After operating the engine for a while pull the vacuum line at the FPR. If it is wet the FPR is defective and needs to be replaced. If it is dry it should be good. Your system sounds like it is working properly to me.

 

ok, so besides a ground on the fuel pressure guage, no one has any clues? what should i be looking for besides a ground on the guage? on my 02 sensors i'm showing 840 at wide open throttle ( the one or two times i dared to go there!!!! ) so it's extra lean. There's a fuel pressure issue here, not a guage. unless it's in the pcm programming, which i've been told a thousand times it's not.

 

The PCM does not control the fuel pressure, if you are seeing the pressure drop it is a mechanical issue. Make this 1001, its not the calibration.

 

...

 

The fuel filter is in the tank, and is replaced at the time of the pump install.

 

Here is my imput. Buy a STS and go faster

 

Since you've replaced darn near everything mechanical. How about something electrical. Read the post about a loose ground. Can you verify you are keeping 12-14 volts to the pump?