I hooked up a fuel pressure gauge.
Key on engine off I had almost no pressure but heard the pump. I cycled the key to the on position about ten times, each time gaining about 5 psi, until I was able to get the gauge up to 40 psi give or take.

I then started the car and the pressure dropped to 32 psi. And idled there for about 10 min without fluctuating much.

I then turned off the engine and the pressure dropped to about 28 psi. Over the past ten min. With the engine off it has climbed back up to 32 psi.

What am I looking at? Pump, fpr, filter? Or is everything ok?

The reason why I am doing this is because I have some egr codes 31 32 34 along with code 41 which is lean condition.

All my vacuum hoses were shot so I replaced those with new rubber lines but i still have a bad idel.

 

I just primed the system a few more times by reliving the pressure and then turning the key to on. It now climbs to 20 at a moderate speed, and then like 3 seconds later I hear a click and it jumps right to 30.it has done that about 5 times in a row now.

 

Not nearly enough pressure. You didn't say what year and motor it is, but all the v-8's and the 94 up 6's require 30 to 45 psi. Below 30 it won't run so you see the problem, you want more like 42-43 KOEO. Pre 94 6's require 45 to 60 psi.
Very possibly (most likely) a faulty pump but first pinch off the return line with some needle nose vice grips or such to check the pressure then, just in case the fuel pressure regulator is the problem (not very likely, but you can hope).

 

I reset the computer. Took the truck for a spin until my check engine light came back on and I pulled into the garage.

As I was pulling in the truck was really idling bad. Almost stalling out. I pulled code 41 again. All egr codes didn't really appear since my vacuum line replacment. I sprayed either everywhere and didn't get any change in engine idel.so I don't think I have a vacuum leak.

Next I read up on the internet for about 30 min. And when I went out and did a KOEO test again, I had to turn my key about 10 times again to get the fuel pressure up to about 38.

After 20 psi or so it starts to climb fast.

What gives? I've been realing like crazy but can't find any good info. I don't think it's a bad O2 sensor.

 

I have a 92 5.0 with dual tanks.the truck has sat along time. The previous owner and the owner before him never used the front tank.

Before I start dropping a tank, should I try using the front tank? I feel like that's a bad idea. Also how can't I be certain it's not a filter or a fpr?

 

Change the filter.
Pinch off the return line and see if pressure builds.
If it has trouble building pressure but holds the pressure for a few minutes after it does build it up, you're usually looking at a pump problem (could be a pinched or clogged line or filter, but quite often the pump is the issue.
Mine goes to 42 psi in one second and holds it, as an example.

 

ok i replaced the filter but my fuel pressure gauge broke so i wasnt able to do the FPR test.

Here is the new question. Im getting 32psi KOER. that is within spec. sure i may have a fuel pump problem as well but if at idle im getting 32 psi then that should not cause my truck to idle like complete crap. the engine revs really fast at first then dies down and usually holds fairly steady with a little bouncing. but if i go for a drive around the block, by the time i get back to my house my truck is running and idling like complete crap. almost dying. Also when i first take off on a cold start with a little gas it will run ok, but once it heats up it really starts acting up.

My only code is a 41 which could be due to fuel pump but given the info above i have to believe there is another issue going on. Im not sure if its actually an o2 sensor or engine temp sensor or what.

Lots of people have viewed this with just one guy replying. Please give any input.

Also i have replaced all vacuum lines that i could see. i also sprayed starter fluid all over looking for any other leaks with no success.

 

When I had an O2 sensor issue, my truck would run ok in open loop (cold) but as soon as it warmed up (closed loop) it ran like crap, no power; bogging out.
That was the O2 sensor. A new one fixed the problem.
That might help with yours.

 

We're you getting a code 41?

Also when it was hesitating and bogging, was that only with light gas pedal. It seems like if I floor it, it will get going.

What's a good way to test this sensor? Also what brand is best in these bosch? Or just go straight to ford.

 

I replaced mine with a $25 bosch sensor - amazon or rockauto.

I'd get another fuel pressure gauge and re-measure - you can pull the vacuum line off of the FPR and see if it smells like fuel - that's usually a sure sign it has given up the ghost.