2005 F-150 SCREW 5.4L 3V 4X4
I am getting some hesitation on acceleration. In particular while in motion.
My average fuel pressure is about 39psi, but it if I hit gas hard it dips momentarily to 29psi. This does not seem right to me. It also feels like it should have more power anyways.
Back when fuel regulators were vacuum and inexpensive I'd just throw that at it and see if it helped (especially before the $$$ and time for pump).
This does seem more like fuel pump problem (not enough volume?) than a fuel pump driver to me. Does this sound logical?
FWIW, it is a brand new motor and ignition system. No codes.

Thanks!

 

did you do a quick visual inspection of the driver module?

 

I've looked a bit at it... considered removing from mount to check for the dreaded corrosion, but every failure I've read about presents with erratic pressure, no starts, rich burns....
My symptoms seem minor (though potentially more expensive).
Have you seen such symptoms with the module?

 

How many miles? That is pretty Low fuel psi. I would start with a fuel filter, i never seen a plugged fuel filter cause that low pressure, but it is possible. Unless it has been changed recently.

 

If you pull the vacuum source off the regulator, pressure should go up. Then with the line off, if you goose the throttle and the pressure drops significantly then raises back up, the pump likely is weak. The regulator actually keeps the pressure from going too high and is often replaced when it is good in hopes of raising low fuel pressure. The regulator is bad if the diaphram has ruptured, sending raw gas into the vacuum line connected to it.I would be looking at a fuel filter being restrictive, limiting the volume of fuel flow.

 

Uh, he doesn't have one of those.... It's all electronic.

 

The filter and injectors are all less than two years old.

 

Are you using a mechanical in-line fuel pressure gauge to measure pressure or are you using the FRP sensor's output as reported via the PCM/scan tool?

A sag in the pressure under heavy load usually indicates either a restriction in the delivery system or a weak pump.

 

As you may be aware of, the Ford geniuses decided to do away with the shrader valve that wold make the gauge check easy - I don't have the adapters I'd need to check line pressure. So, I am using PCM live data.

 

Ok... so out of curiosity, I decided to remove (and plug) the vacuum line from the sensor/sender. This reduced the hesitation (though I did still get my intake backfire). My pressure only dipped to just shy of 35 PSI. Obviously, if I remove the vacuum reference, I'd expect it to behave differently. Still not codes though... thoughts? Other that why did the do away with the schrader valve???!!!???!!