Fuel Pressure Problem....Help!

[vbguy01]

I just got my ported blower on. I put on a 2.76 w/idler. During the dyno, noticed AF near 16 across the board. Dyno was aborted around 4k rpm. Car was running way lean. Still waiting on a custom tune from James so I haven't messed with the tune yet. These results were not normal. Checked the fuel pressure by the blower and was nominal, with the car running px was around 30psi (10psi low).

So, am I looking at a clogged fuel filter or a bad pump or something else? I am hoping to avoid taking it to Ford if I don't have to. If I do, I'll lose the idler and replace the pulley cover. I should be fine since I haven't touched the puter yet. Anyone ever had or heard of this problem?

Just a little backround...The car has 17k miles, daily driven, no prior problems, ran at track on Tuesday (12.8). The car drives fine otherwise. I kept it out of the boost and below 3k rpm until I get the tune (and more importantly this problem fixed)

Help...

 

[Lightning Tim]

Originally posted by vbguy01

So, am I looking at a clogged fuel filter or a bad pump or something else? I am hoping to avoid taking it to Ford if I don't have to. If I do, I'll lose the idler and replace the pulley cover. I should be fine since I haven't touched the puter yet. Anyone ever had or heard of this problem?

Help...

Sounds like one of the 2. Your idle fuel pressure at the rails is always supposed to be 40psi right? 10 psi low like you said.

I would change the filter, maybe flush out the line with an air hose, take the injectors out check them, run somekind of fuel system cleaner anything before spending a bunch of money or taking it to a dealer.

Or just wait for the tune first, it could be all it is.

 

[predator]

Just as a precaution check your fuel pressure regulator located on the driver's side at the fuel rail. See if you have any fuel in your vacuum lines or if your oil smells of gas. Symptoms you have could be related. The part has been known to fail. Change the part--$60, clear vacuum lines and change the oil before it goes another mile.

 

[05 Roush]

Isn't fuel pressure also affect by low voltage?

 

[n2fords2003]

Re: Re: Fuel Pressure Problem....Help!

Originally posted by Lightning Tim
Sounds like one of the 2. Your idle fuel pressure at the rails is always supposed to be 40psi right? 10 psi low like you said.

I would change the filter, maybe flush out the line with an air hose, take the injectors out check them, run somekind of fuel system cleaner anything before spending a bunch of money or taking it to a dealer.

Or just wait for the tune first, it could be all it is.

NO Idle will be 30 psi

 

[jumpinjackflash]

The fuel pressure should be about 30 psi at idle.

The pressure across the injector is always supposed to be 39psi unless the tune has been modified. At idle the pressure in the intake is about -20inHg or about -10psi. So the pressure in the fuel rail should be about 30psi to have a 39psi drop across the injector. It sounds like your fuel system is working.

You might have a leak in the intake system somewhere that is allowing unmetered air into the system. Make sure all the vacuum lines were reinstalled correctly and make sure there are no leaks around the TB, intake tube, etc.

You said you just got the ported blower put on. Doesn't it seem much more likely that the problem is related to the stuff that was just messed with? Check there first.

Good Luck!

 

[vbguy01]

I'm a bit puzzled as to how this came to be a problem. The car ran fine to my knowledge at the track 2 days earlier. Now I'm hearing if I jump on it I will blow my motor. I'm not the most mechanically gifted or knowledgeable person when it comes to modding. Hence I don't do much more work than change the oil. This is a bit over my expertise level. The guys who ported the blower are quite experienced at doing them, so I would doubt it was something they overlooked. Now I'm not sure who to turn to. I won't feel comfortable running the motor hard until I see the results on a dyno. I'm not sure I want to take it back to Ford and have them check it out. (They could run it up and blow the motor???) without a dyno. Maybe put it on another dyno and get a second opinion... If I remember right, the car was putting out 30psi with the throttle down not at idle. That would be low psi no? And even prior to changing the tune would you see close to 16 AF across the board?

 

[DrUnKeNmAsTer]

I would check out another dyno. I just had mine dynoed with about 27 other cars and almost all of them were running lean. Turns out that the wideband that was checkin a/f went bad. They cut my dyno run @ 3200 r's and said my engine would blow. They said I might have a bad pump. I checked the pressure and it was fine, 30 psi @ idle and 50-55 @ WOT. 16 across the board sounds like they had a "lazy" wideband.

 

[vbguy01]

Originally posted by DrUnKeNmAsTer
They said I might have a bad pump. I checked the pressure and it was fine, 30 psi @ idle and 50-55 @ WOT. 16 across the board sounds like they had a "lazy" wideband.

Aren't the stock pumps supposed to put out 40psi at WOT?

It can't hurt to throw it on another dyno. (just $) I still saw a low reading on a hand held gauge though so it may be something else. Weird.

 

[Quadcammer]

the returnless fuel system is based off manifold pressure.

as has been stated.

at idle (20 in HG)/2 you get around 30 to 32 psi.

at zero vaccum, you get the delta value of 39.

now once you are in boost, the fuel system adds 1 psi per lb of boost.

so basically rail pressure-manifold pressure must equal the delta pressure of 39 psi.

 

[vbguy01]

I think I'll just put the stock pulley back on and have the ford guru's give the fuel system a checkup.