cscjjd

Hi,

I got the following fuel pressures on my 2004 F150 Heritage 3.6 L (131K miles)…
key on: 28 psi......idle: 32 psi
idle with vacuum removed from fuel pressure regulator: 40 psi

The pressure should be: key on: 35-45 psi......idle: 28-55 psi
(notice the key on pressure should be more than the idle pressure)

The other test I attempted to perform was to pinch the fuel return line. I was not able to do this test because…
1. I was not sure which line was the fuel return line - I suspect it was one of the two lines going into the fuel rail.
2. When I tried to pinch the “flexible” part of the two lines going into the fuel rail, they were too hard to pinch using my fingers as they seem to be covered with a ribbed protective sheathing. I was afraid to pinch them with pliers as I thought it might do damage.

I should also mention that the battery is too weak to crank the engine even when the charger was on it over night.
(I measured the “key on” pressure (28 psi) after I connected the jumper battery to the dead battery - at which time the dead battery was measuring just above 12 volts).

The main codes I have had are…
P0133 (O2 sensor slow) P0174 (system too lean) P2196 and 2198 (O2 sensor stuck rich)
…so I am ordering two new O2 sensors

I have checked for vacuum leaks, pvc, MAF, changed fuel filter and spark plugs. Fuel pressure holds for at least 5 minutes after key is turned off. Fuel flow is .4 gal/hr at idle, 1.3 gal/hr at 2000 rpm.

My main question is whether this indicates a problem with the fuel pressure. If so, what should do next? The truck is idling roughly, surging, and barely running when I drive it.


Thanks guys.

Mod (Ret.)

There is no fuel pressure regulater on the late 2004 to 2008 (and up) Ford F150's. They use a FPCM (fuel pump control module) to turn on, turn off the fuel pump, based on a signal from the PCM (powertrain control module). The powertrain control module gets its input from a fuel pressure sensor.

Ford went to this setup when they used a single fuel line from the gas tank to fuel rail, to prevent vapor lock conditions.

Maybe the heritage was different. Do you have two fuel lines? One being a return line?

If so, you may do better posting this in the 1997 to 2003 tech section, as the heritage model was an early 2004 release. Not like the late 2004 to 2008 this section is known for.