I have an '06 F-150 in my nephews shop that has a strange pressure reading. The truck has a 5.4 engine and auto tranny.(54K miles)

the pressure is only 28 lbs and only rises to 31 lbs when I remove the vacuum hose on the pressure regulator. all these readings are not constant, the 28 lbs constantly moves from 25 to 28 and the 31 lbs/vacuum off one moves from 29 to as high as 34. the scanner showed a misfire on # 8 cylinder, but every time I cut the thing off, it shows a different cylinder misfire.

I've cleaned the injectors and replaced the fuel filter. the fuel filter had some fine brown crud in it. has there been any problems with late model ford gas tanks ?

I'm guessing that the fuel pump need replacing, but need some ideas from you guys about anything that I might not have known about. this is the first one of these that I have attempted to work on.

thanks, J

 

not sure on the specs but im sure it sould be at least 40lbs but probably more

 

since our shop scanner wouldn't communicate with the truck, the customer carried it to the nearest Ford "stealership". they told him that #6 & #8 fuel injectors were stuck open and needed replaced. they wanted an arm and a leg for repairs, plus $300 for a system flush (whatever the heck that is).

the guy is going to buy 2 injectors tomorrow and bring it back to us to replace them. somehow, I just don't believe two stuck-open injectors could cause low and fluxuating fuel pressure. tomorrow should tell the truth one way or another.

I'll post the results.......I always want others to complete the story, so I'll give them to the readers here when I get them.

.
.

 

We have had problems with stuck open injectors. I just got done replacing #2 and #5 on an 05' F-150 for a very small leak that was causing an extended crank issue in the mornings. I had to remove the entire fuel rail and pressurize it with our injector flush machine and then wait for a while to even see the puddle form in the injector. But it was enough of a leak that after sitting all night, pressure would drop and at first crank would need to crank longer to build that fuel pressure. You can pull the fuel rail up out of the intake(remove the 4 8mm bolts). Then set a folded up shop rag under all the injectors. Have someone turn the key to ON and watch for any fuel leaking out of the injectors. however in your case, it could be a bad pump causing the concern.

P.S....KOEO pressure should be above 40 psi. I believe the truck I just did had a KOER pressure of around 43?

 

the customer didn't bring the F-150 back until today.

the injectors were changed out and the truck leveled out and ran without any noticable miss. the fuel pressure still fluxuated as the truck ran and was still around 32-33 lbs on the high side.

the customer was satisfied, but I feel he will be back (did I mention that he was a lawyer/prosecutor ?). I believe the fuel pump will need replacing fairly soon. without pulling the tank, I believe someone he prosecuted has put something in his tank and the rotary type fuel pump is slowly being eaten up. time will tell.

.
.