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Fuel Pump or Fuel pressure "dampener"

MyTruckNow

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So I have had a problem with this truck since i bought it.

I was getting lean codes, I tried the mass air flow sensor..didnt fix it. I checked for vacuum leaks none.

I brought it to a buddy of mines garage and they did a fuel pressure check.

When you turn the key it does have pressure, but than the pressure goes down. ( im told it should hold the pressure)

When running, the pressure is about 10 to 15 psi too low.

So either its the fuel pump, the fuel pressure regulator on the fuel pump. OR the fuel pressure dampener see it here http://www.stockwiseauto.com/produc...Year/2001/Make/Ford/Model/Explorer Sport Trac

Problem is I dont want to buy a 300 dollar part, if its the fuel pump or fuel pressure regulator on the fuel pump.

Does ANYONE know how i can test it to see what it could be?

ANY help would be very appreciated this has been a problem for 2 years ( i have 2 year old inspection sticker on the thing..)
 


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JusTheUsual

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I bought my dampner at Rockauto.com for $40-$60 last year. I would bet it's your fuel pump. My dampner when it wouldn't work right I would be missing like half the horsepower
 




MyTruckNow

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I bought my dampner at Rockauto.com for $40-$60 last year. I would bet it's your fuel pump. My dampner when it wouldn't work right I would be missing like half the horsepower


Thanks for your advice, im really stumped here.

I look at that site, the ones they had were around 200. There was one for 50 but it was for a sport trac, I have the sport.

Im suprised there is no way to diagnose these things, without just playing the lotto with buying new parts.

From what I can tell the dampener, just stops sudden fuel pressure from hitting the rail too hard. If that's all it does, than i cant see that being the issue here, since when the car is on the on position, the pressure goes up, but than starts to go back down ( Not started ). i cant see that "dampener" if thats what it is making it do that, unless it acts as some sort of one way valve to not allow fuel back to the tank..what do you think?

Mine idle roughs, and there is a lack of power. If i just smash the gas pedal, it takes a while to go to full rpms..But it does have power, becouse i have towed a few people out of ditches with it. And it handled it well.

Thanks for the reply btw!
 








MyTruckNow

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SoNic67

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Sounds like a fuel pump issue - it should hold pressure, because it has a check-valve inside.
 




MyTruckNow

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Sounds like a fuel pump issue - it should hold pressure, because it has a check-valve inside.

There is also something called a "fuel pressure dampener" its on the rail. My buddy who checked the fuel pressure says it could be that. But I need a way to test it. Because that dampener is 300 bucks.
 




Runnin'OnEmpty

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......
When you turn the key it does have pressure, but than the pressure goes down. ( im told it should hold the pressure)

When running, the pressure is about 10 to 15 psi too low.

.......
That sounds like you have a split in the feeder line going
from the fuel pressure regulator to the hard line inside
the tank. Pressure is being relieved through the split hose
when the pump stops, and the split is also reducing
running pressure.

I noticed a split in my hose when installing a new pump
recently; it was where the clamp tightens on the regulator
nipple.

Be sure to replace the hose with at least SAE 30R10
hose, rated for submerged fuel use. And use F.I. clamps,
not the more common screw type. I'd replace the pump
too, since the labor is the same for both jobs.
 




MyTruckNow

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That sounds like you have a split in the feeder line going
from the fuel pressure regulator to the hard line inside
the tank. Pressure is being relieved through the split hose
when the pump stops, and the split is also reducing
running pressure.

I noticed a split in my hose when installing a new pump
recently; it was where the clamp tightens on the regulator
nipple.

Be sure to replace the hose with at least SAE 30R10
hose, rated for submerged fuel use. And use F.I. clamps,
not the more common screw type. I'd replace the pump
too, since the labor is the same for both jobs.

Id I replace the whole sending unit, will it come with that hose you had mentioned? http://www.autozone.com/fuel-delive.../6-cylinders-e-4-0l-efi-sohc/559716_947475_0/
 




swshawaii

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2000StreetRod

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fuel pressure damper

There is no return line from the fuel pressure damper to the fuel tank. The only way the fuel pressure damper can affect the static fuel pressure at the Schrader valve is if the diaphragm is cracked and fuel is leaking into the intake system via the vacuum hose. When that happens you might find fuel in the vacuum hose when it is disconnected from the damper. The diaphragm is easily checked for leaks by connecting a hand vacuum pump to it and seeing if it holds vacuum.

Fuel is basically incompressible and inexpansible at reasonable pressures. Every time a fuel injector changes from open to closed there is a pressure pulse propagated along the fuel rails. The fuel pressure damper reduces the pulse in a similar manner to the way air chambers in a home water supply system prevent water "hammering".

I suspect the source of your low fuel pressure is either a weak fuel pump or a split in the intank fuel pump outlet hoses.
FPAssy2.jpg

A less likely possibility is a defective intank fuel pressure regulator.
 




david4451

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If you can hear the fuel pump working, then it is probably a split in the fuel hose inside the tank or a blocked fuel filter.
 




SoNic67

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A blocked fuel filter won't let the pressure go up and then back down as described.
 




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My local ford dealer called ford main office since they have replaced fuel pump and regulater in the fuel tank on my one fuel line system and still having problems with low fuel pressure.They advised us that the fuel damper also controls fuel pressure.
 




2000StreetRod

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My local ford dealer called ford main office since they have replaced fuel pump and regulater in the fuel tank on my one fuel line system and still having problems with low fuel pressure.They advised us that the fuel damper also controls fuel pressure.
I doubt that although I don't know specifically about the Sport Trac. It is my understanding that the fuel pressure regulator is in the fuel pump assembly located in the fuel tank. In 2004 (as I recall) the fuel pressure damper was replaced with a fuel rail pressure/temperature sensor that allows the PCM to control fuel pressure via pulse width modulation of the fuel pump. I incorporated the fuel pressure/temperature sensor on my engine when I added a high flow fuel pump and controlled it with a pulse width modulator.

FPSensor2.jpg


fp_purple3.png
 




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I should not have listened to ford tech. After sending another five hundred dollars I made it about 15miles before check engine light coded lean banks 1 and 2. It has not been but six weeks ago they replaced fuel pump and regulator in the tank. Fuel pressure is only 42 psi. It is bad when ford dealer can not fix it.
 




2000StreetRod

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I should not have listened to ford tech. After sending another five hundred dollars I made it about 15miles before check engine light coded lean banks 1 and 2. It has not been but six weeks ago they replaced fuel pump and regulator in the tank. Fuel pressure is only 42 psi. It is bad when ford dealer can not fix it.
Has the fuel filter been replaced in recent years? It can become clogged and restrict flow. Make sure the correct fuel pump assembly was installed. As I recall the normal 2004 and later fuel pressure is around 40 psi. I suspect when Ford switched to the pulse width modulated fuel pressure control system the intank fuel pressure regulator was changed from 65 psi to around 45 psi. That way if the fuel pressure sensor failed (which is fairly common) the fuel pressure would default to around 45 psi.
 




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My sport trac is a 2001 model. Built in 04/2000. My system only has one fuel line.And it has a new fuel filture when they replaced the first fuel pump.My fuel pressure is 42 psi at idle. The only codes is lean bank 1 and 2. They also replaced filler neck hose and fuel tank code was resolved.
 




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The problem is in variable volts this system uses.They thought it may be a bad ground so they ran a separate ground wire from battery to fuel pump in the tank.I have got ford engineers helping my local ford service dept figure out what the problem is. When we fix the problem I will post it.
 


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Royy

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Did you ever figure out what caused this?

I had (have?) the same problem with my 2003 Explorer. Fuel pressure issues, which the mechanic diagnosed as a bad fuel pump. They replaced the fuel pump and filter, and I then also replaced all the injectors.
Worked fine for a while, then after a couple of weeks the issues returned, eventually leading to lean codes.

I took the car back to the mechanic, and he said that the fuel pressure damper was bad, which had caused the fuel pump to go bad. I'm not sure whether that's even possible. Plus, the damper is one of the first things I checked when this issue first came up, and I didn't see any of the telltale signs of it being broken. Anyway, I only just got the car back, so I haven't driven it enough yet to know for sure whether the problem is fixed for real this time,
 




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