96 f150 4.9 2wd.
key on, engine off its 30psi. Running it's 42psi. After cutting it off it went to 50psi and stayed. When revved, it bumped down to 36-38psi.

Reason I ask is because I'm getting lean on bank 1/bank2 and trying to see if this is it. I changed the fuel filter. But truck idles rough and acts like it doesn't want to start half the time like it's getting no fuel, and after driving and restarting the truck, it stumbles for a second before idling somewhat normal.

 

No your fuel pressure is not good.
When revved, it should be bumped up to around 60psi.

 

does the truck have dual tanks? same FP on both? like subford said, that's no good.

 

single tank

 

The needle was very shaky while running on 42. I don't know if that makes any difference. But every other reading it was smooth and steady. Only shaking while the truck was running

 

My next question is do I need just the sending unit or do I need to get a new hanger unit too

 

Explain 42.

 

fuel pressure was at 42 while running but the needle was very Shakey on the gauge

 

Should I start with fuel pump or fuel pressure regulator?

 

Sounds like the fuel pressure regulator is working OK.

It is hard to say if you have a bad fuel filter, low voltage at the pump or a bad pump or plugged sock below the fuel pump.

 

I have very recently changed the filter, the other one was less than a year old and wasn't very dirty at all. I had to replace the filler neck hose a month or two back, and went ahead and changed the sock on the pump as the old one was very ditry. I've had this issue since I've owned the truck though. So maybe it's been the pump all along?

 

Initiate the fuel pump self test (key on engine off) and climb under, listen to the fuel pump. More often than not, a weak pump makes funky noises or is overly loud.

 

It just makes a humming sound for a second or two when I turn the key on then nothing else. What else would cause the pressure to be low?

 

Right, there's a test that you can perform to run the fuel pumps continuously, all you need is a paper clip. I'm sure subford has a diagram handy of the test port and its location.

 

Sorry there is no diagram that I know of for a 1996 F150 OBD2 truck.
I think there may be some scanners that will do it but not with a paper clip.



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