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Expedition Fuel Pressure Drops Off

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Old 12-27-2008, 03:35 PM
Junior Member
Join Date: Dec 2008
Vehicle: 2001 Ford Expedition
Posts: 3
Expedition Fuel Pressure Drops Off

I have a 2001 Expedition Eddie Bauer 4x4 with the 5.4L engine. The vehicle has 103K miles on it.

The problem is the fuel pressure drops off under load. Pressure starts at about 32 psi and drops to 18 psi under heavy load/high RPM (4000 and up). This causes low power and ping/detonation noise. Do get a P0300 code, random cylinder misfire.

A mechanic has looked at it and replaced the fuel filter with no change in behavior, he then changed the fuel pump. This did not fix the problem either. ***Correction the fuel pump change did fix the fuel pressure drop under load.

If you disconnect the fuel regulator the fuel pressure goes up to about 40 psi. However, when you drive the vehicle the same thing happens, pressure drops off under load and high rpm.

The same mechanic changed the intake manifold due to the COP's bolts being stripped out and there for was unable to remove them to change the plugs. A Ford OE intake was not use. An OEM manifold was used and came from these guys, http://www.stevensparts.com/EXHAUST%...DS%20INDEX.htm

I did check with two other people who used this OEM manifold from Steven's Parts before installing it on my vehicle. Both people said it worked just fine. Car runs well.

Not sure what to look at next.

Any help on the cause of this problem would be great.


Last edited by tbyle; 01-15-2009 at 08:22 PM.
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Old 12-28-2008, 09:39 AM
Senior Member
Join Date: Oct 2002
Location: St. Louis (Out in the woods)
Vehicle: 2001 Ford F250 6.8
Posts: 5,748
Try driving with the fuel cap removed while monitoring fuel pressure (ignore probable CEL/SES or gas cap message). If delivery pressure now works correctly, the tank venting is restricted.

Sounds like it's either restricted fuel delivery or restricted venting. You've covered the common stuff on the delivery side. Of course, it still might be a restriction in one of the supply lines.

If your original owner's manual is missing, download a soft copy from www.fleet.ford.com under the PARTS AND SERVICE tab.

1995 Mustang GT Convertible, only 68K miles. 2000 Ford Contour Daily driver.
2001 F250 SD, 6.8L, 4 X4. 2007 Mercury Mariner AWD - Wifey's daily driver,

Timesert 5553 kit available for rent, PM me.
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Old 12-30-2008, 03:22 PM
Junior Member
Join Date: Dec 2008
Vehicle: 2001 Ford Expedition
Posts: 3
Here is an update and closure to the problem. I felt it important to follow up with a final post since finding the cause of problems as well as solutions to problems is what this forum is for.

The heart of the problem was the right side catalytic converters. The upstream converter failed and took out the downstream, as always.

How did we find this?
Well, after changing the fuel pump the pressures were better, but the car still had a power issue under load and at higher RPM's. I originally said the pressure still dropped off after the pump change. However, I have since confirmed that the fuel pressure drop was fixed after the fuel pump change.

Back to how we found the issue. We took the car for a good hard drive with a fancy Ford scanner connected. We saw some interesting results so we recorded the scanner readings while driving the car hard and experiencing the problem. We had to record the information on the scanner because the info changes so quickly on the scanner readout it was hard to see what was going on.

While reviewing the data on the scanner, we saw that cylinders 1,2,3 and 4 were shutting down and just plain having problems. What is common with all cylinders on one side the engine? Exhaust! We felt confident fuel and air supply were good and with new plugs we felt spark was good too.

We then disconnected the exhaust on the right side and went for a very loud and quick drive. The car ran like a champ!

Installed new converters and all better now.

The mechanic I worked with is quite good. He worked for Ford for 15 years. Originally everything pointed to the fuel pump and I completely understand how he came to that conclusion. However, the fuel pump didn't fix the problem. These pumps are expensive and not returnable once installed. So we made a deal. He only charged me his cost for the catalytic converter change as well as the cost of the new fuel pump. No labor at all!

I felt this was fair so I paid the bill. The fuel pump didn't need to be changed. However, the car now starts perfectly/instantly while before it took a couple seconds of cranking to start.

Thank you for the replies and info.

Happy New Year !!!

Last edited by tbyle; 01-15-2009 at 08:20 PM.
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