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Allright... I've tried to summarize this post because the other thread was too long and got off track. Still no resolution or ANYONE that has the same problem.

Ok guys... I'ma need the pros to figure this one out. I have an on-going year long problem that has me doing nothing but scratching my head and debating lighting this car on fire. I have a 1998 Gt and I'm having what I believe is a fuel problem. Basically I can get the car started, it takes a few tries, but it will start and idle. Now if I hit the gas it will sputter out and die (I can hear my K&N suck air but the RPMS die out), however if I feather the gas and press on the gas slowly the RPM's will climb and I can put it in gear and go. The car runs very sluggish and I must keep the RPMs high to keep it running (seems above 2k RPM's is the sweet spot) It also idles at about 500 - 1k rpm's. Now the car will only start up and drive if I have MORE than a half tank of gas, anything less it will not start and thats where I get really confused.

So far, I have replaced the Fuel Filter, the fuel pump, the MAF sensor (a junkyard one - so Im questioning if it operates), the Fuel inertia switch in the trunk, and now I replaced 2 of the 02 sensors. And there have been no changes in preformance. I eyeballed the O2 sensors once my stang gave me codes 171 and 174. (Bank 1 and bank 2 fuel is lean) I pulled out the rear 2 o2 sensors and the problem got drastically worse so I thought I was on the right track. I put them back in because I assumed they worked since the problem got worse. Now I changed the two front ones only, fired up the car... and got no change. The car did not throw me any codes after about 20 minutes of sluggishly driving it around but the problem has not changed.

The fuel tank is spotless clean on the inside, I detached a fuel rail to make sure fuel was flowing to the engine and that was fine as well. It has 145k Miles on it and no major upgrades, just a K&N intake.

Any ideas would be greatly appreciated... Cmon guys, lets get my baby back on the road!!! It has a sweet new red paint job... It's the nicest broken down vehicle you'll ever see lol.
 

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ok thats wierd i was gonna say mabye something to do with the injectors or mabye even the coils firing but where u said u have to have over half a tank to start it and drive it home really confuses me.:headscratch:

i remember when u posted last time sorry to hear u havent been able to fix it yet that sucks having to spend money and not even knowing if it will work or not, it reminds me of the problems im currently having with my explorer sometimes i want to shoot it to and put it out of my misery. :so
 

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Allright... I've tried to summarize this post because the other thread was too long and got off track. Still no resolution or ANYONE that has the same problem.

Ok guys... I'ma need the pros to figure this one out. I have an on-going year long problem that has me doing nothing but scratching my head and debating lighting this car on fire. I have a 1998 Gt and I'm having what I believe is a fuel problem. Basically I can get the car started, it takes a few tries, but it will start and idle. Now if I hit the gas it will sputter out and die (I can hear my K&N suck air but the RPMS die out), however if I feather the gas and press on the gas slowly the RPM's will climb and I can put it in gear and go. The car runs very sluggish and I must keep the RPMs high to keep it running (seems above 2k RPM's is the sweet spot) It also idles at about 500 - 1k rpm's. Now the car will only start up and drive if I have MORE than a half tank of gas, anything less it will not start and thats where I get really confused.

So far, I have replaced the Fuel Filter, the fuel pump, the MAF sensor (a junkyard one - so Im questioning if it operates), the Fuel inertia switch in the trunk, and now I replaced 2 of the 02 sensors. And there have been no changes in preformance. I eyeballed the O2 sensors once my stang gave me codes 171 and 174. (Bank 1 and bank 2 fuel is lean) I pulled out the rear 2 o2 sensors and the problem got drastically worse so I thought I was on the right track. I put them back in because I assumed they worked since the problem got worse. Now I changed the two front ones only, fired up the car... and got no change. The car did not throw me any codes after about 20 minutes of sluggishly driving it around but the problem has not changed.

The fuel tank is spotless clean on the inside, I detached a fuel rail to make sure fuel was flowing to the engine and that was fine as well. It has 145k Miles on it and no major upgrades, just a K&N intake.

Any ideas would be greatly appreciated... Cmon guys, lets get my baby back on the road!!! It has a sweet new red paint job... It's the nicest broken down vehicle you'll ever see lol.
The best way to check out your fuel pump is to install a fuel gauge at your fuel rail. Your fuel pump has to maintain a constant amount of pressure for your engine to run right. Not sure how much pressure your 98 GT is required to have. You need to find that out through repair manuals or from someone on the forum. Even brand new fuel pumps have been known to go bad. From what you are saying about your rpm's, it sounds to me like you have a vacuum leak somewhere. I had a Chevy engine that responded the same way as your engine is responding. It turned out that I had a major vacuum leak at the brake booster connector. I'm talking about the plastic connector attached to your brake booster. Check out that area with a fine tooth comb. Disconnect every vacuum hose that runs to and from that connector. My gut feeling is you have a bad vacuum leak somewhere. Check out all of your vacuum lines running to and from your throttle body, and your PCV as well. You could also have a defective PCV valve which may be sucking crankcase ventilation. This has happened to me as well. All of your vacuum hoses need to have a snug fit, not lose at all. Let us know what you find! Good luck, Tommy.
 

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Thats definitely a wierd problem with the fuel level, I'm not sure what would cause that, but the rest sounds like an ignition problem to me, check the coils, wires, plugs and make sure all are working right, especially the coils make sure they have enough output voltage. You should also look for vacuum leaksand check all your connections. The fuel level issue is very unusual, maybe check the relays.
 

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The thing about your gas tank at 1/2 tank it won't start at all. Is it possible that your fuel gauge is not reading correctly. Perhaps at 1/2 tank, you are actually at and empty or near empty tank. When ever my son's 2003 GT Mustang read 1/4 tank, he was actually at an empty tank. His engine would die out and not restart at a 1/4 tank. I'm currently troubleshooting his fuel gauge and anti-slush module. Do you have an after market cd player, or video player or amps installed? If yes, who installed it? Let me know. I have important info on this! Because of the way your rpm's are responding, that surely sounds like a vacuum leak to me! Thank you, Tommy.
 

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Discussion Starter #6
Thank you guys so much for your responses. Looks like the consensus may point towards a vacuum leak. I've been told that before, thats what I'll focus on this weekend. :bigthumbsup

To pour salt into the wound, the 69 Chevy pickup I have been driving just took a dump on me as well. Looks like a minor battery issue so it should be good soon. Fixing two cars at once without a daily driver = insanely frustrating.

For a vacuum leak.. is there an easy way for me to locate this? Like spray starter fluid or something? I don;t know.. it's hard to stay motivated to work on this when everything I fix has no effect on the problem. "sigh"
 

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Did you ever get a fuel pressure reading off the fuel rail?

It should be around 32 psi at idle and close to 40 psi with no vacuum, while engine is under load.
 

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Discussion Starter #8
Did you ever get a fuel pressure reading off the fuel rail?

It should be around 32 psi at idle and close to 40 psi with no vacuum, while engine is under load.
I actually did that just this weekend and I pray I'm on the right track.

This weekend I checked for vacuum leaks... there are none present. So I can scratch that off the list. I did test the fuel pressure and it sat at about 13-14 PSI at idle and if I shot the RPM's up it stayed exactly the same. So now I'm eye eyeballing the fuel pressure regulator. So I have a couple questions. Below are some links to pics of what I'm looking at.

http://i237.photobucket.com/albums/ff22/AFehler/1237840642.jpg

For the pic above you can see I took off the tube to my K&N and to the left there is the bright shiny silver part. I'm assuming thats simply and in-line filter. It has no vacuum attachments. No one can tell me what this is (not even ford even with the part #), it's on the fuel line going into the rail.

http://i237.photobucket.com/albums/ff22/AFehler/1237840640.jpg

the link above is the same as the first pic just a different angle. Now look at the bright shiny part I think is just an inline filter.... just above it to the left of the throttle body there is another chrome part that I think is my fuel pressure regulator. It sits directly on the rail and has a vacuum hose on it... it's actually part of the rail, below is a close up pic of it. You can see the vacuum hose (red hose with the black boot on it) Can someone please confirm if this is my fuel pressure regulator?

http://i237.photobucket.com/albums/ff22/AFehler/1237840640.jpg

Reason being I have been to Ford and numerous Parts stores (Napa, Kragan, LameAss Autozone, Pep boys, worldwide Auto) and everyone gives me a different fuel pressure regulator.

IMPORTANT: My fuel pressure regulator is part of the fuel rail, it does not detach. They are molded together.

I want to know if anyone knows why my stang would be different than others, I don't know if it's a late or early model 98 I'm just confused. Obviously I have to replace the whole rail, which is fine. But I don't know where to get the whole setup, I'm actually spending this next weekend going to wrecking yards in hopes that a wrecked mustang will have a fuel rail like mine. Please guys any help is always appreciated.

This website is a Godsend, thank you all for your help. You all give the best advice. Once again I think I'm on the right track and hope my baby will be purring once again.
 

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Have you removed the fuel injector rail and looked underneath to make sure it isn't bolted on? I had a couple 80's Mustangs and the fuel pressure regulator was bolted to the rail.

I haven't seen the 98 GT's setup though, so it must be different. The part your pictures show is also on the returnless fuel system Mustangs and I have often wondered what it was for as well.

Your fuel pressure is the issue, I would say the regulator diaphram is bad and that it is returning most of the fuel to your tank which would explain the low pressure. You are on the right track.:bigthumbsup
 

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Fuel Pressure Regulator

I actually did that just this weekend and I pray I'm on the right track.

This weekend I checked for vacuum leaks... there are none present. So I can scratch that off the list. I did test the fuel pressure and it sat at about 13-14 PSI at idle and if I shot the RPM's up it stayed exactly the same. So now I'm eye eyeballing the fuel pressure regulator. So I have a couple questions. Below are some links to pics of what I'm looking at.

http://i237.photobucket.com/albums/ff22/AFehler/1237840642.jpg

For the pic above you can see I took off the tube to my K&N and to the left there is the bright shiny silver part. I'm assuming thats simply and in-line filter. It has no vacuum attachments. No one can tell me what this is (not even ford even with the part #), it's on the fuel line going into the rail.

http://i237.photobucket.com/albums/ff22/AFehler/1237840640.jpg

the link above is the same as the first pic just a different angle. Now look at the bright shiny part I think is just an inline filter.... just above it to the left of the throttle body there is another chrome part that I think is my fuel pressure regulator. It sits directly on the rail and has a vacuum hose on it... it's actually part of the rail, below is a close up pic of it. You can see the vacuum hose (red hose with the black boot on it) Can someone please confirm if this is my fuel pressure regulator?

http://i237.photobucket.com/albums/ff22/AFehler/1237840640.jpg

Reason being I have been to Ford and numerous Parts stores (Napa, Kragan, LameAss Autozone, Pep boys, worldwide Auto) and everyone gives me a different fuel pressure regulator.

IMPORTANT: My fuel pressure regulator is part of the fuel rail, it does not detach. They are molded together.

I want to know if anyone knows why my stang would be different than others, I don't know if it's a late or early model 98 I'm just confused. Obviously I have to replace the whole rail, which is fine. But I don't know where to get the whole setup, I'm actually spending this next weekend going to wrecking yards in hopes that a wrecked mustang will have a fuel rail like mine. Please guys any help is always appreciated.

This website is a Godsend, thank you all for your help. You all give the best advice. Once again I think I'm on the right track and hope my baby will be purring once again.
If you have a 1998 GT Mustang with a 4.6 engine, the picture below is what your fuel pressure regulator is suppose to look like. The other item you were asking about shiny silver color item may be a check valve to prevent the fuel from returning to the fuel tank, not sure? I will do some checking on that and get back to you. Hope this helps, Tommy.


 

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Discussion Starter #11
Have you removed the fuel injector rail and looked underneath to make sure it isn't bolted on? I had a couple 80's Mustangs and the fuel pressure regulator was bolted to the rail.
You know... now I'm completely second guessing myself...:scratchchin

I poked around the FPR (pic link below) and I am almost positive it was molded to the rail on the bottom if it. Now I'm over-thinking and I need to look at it again to be sure. So Ima just pull that bad boy out (the fuel rails) and flip it over to check the second I get home today.

http://i237.photobucket.com/albums/ff22/AFehler/1237840641.jpg

hey Tommy (AKA Silver Mustang), Thanks bud. I noticed you tried to help on my other threads as well. I really appreciate the help and hope you got your sons issue figured out. I do have an after market CD player in there. It's an Alpine and I believe Circuit City installed it. I had an amp but it was removed long ago, I do however still have the amp wires (2 or 4 guage) going from the battery to inside the vehicle, but the ends are taped off and are not connected to anything.
 

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You know... now I'm completely second guessing myself...:scratchchin

I poked around the FPR (pic link below) and I am almost positive it was molded to the rail on the bottom if it. Now I'm over-thinking and I need to look at it again to be sure. So Ima just pull that bad boy out (the fuel rails) and flip it over to check the second I get home today.

http://i237.photobucket.com/albums/ff22/AFehler/1237840641.jpg

hey Tommy (AKA Silver Mustang), Thanks bud. I noticed you tried to help on my other threads as well. I really appreciate the help and hope you got your sons issue figured out. I do have an after market CD player in there. It's an Alpine and I believe Circuit City installed it. I had an amp but it was removed long ago, I do however still have the amp wires (2 or 4 guage) going from the battery to inside the vehicle, but the ends are taped off and are not connected to anything.
Glad to be of some help. I can't find anything on the shiny silver colored item. The only thing I can think of, is that it is a one way fuel check valve to keep the fuel from returning to the fuel tank. As for the other matter of where the amp is getting it's power from, if the power is direct from the car's battery, than that would be ok. However, something is triggering the amp to come on, and that is what you need to check on. As for the fuel pressure regulator, one other thing which may help to identify it is, there may be an adjustable screw inside the hole on the top of the fuel pressure regulator. Usually designed for an allen wrench tool. I checked out NAPA Auto parts On-line and they also show another valve that is very similar to the fuel pressure regulator which is also suppose to be in your fuel line system, so you have to make sure you are dealing with the right item. I'll see if I can find some info on that valve and post a picture here. Good luck, Tommy.
 

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Fuel Pressure Damper

Ok, this one is called a Fuel Pressure Damper. It has a different part number from the Fuel Pressure Regulator, so, they probably serve two different functions. Both items are listed for a 98 GT Mustang with a 4.6 engine. So, look for this one to see if it is attached to the fuel rail in anyway. I just had a thought. Check that silver colored item again, perhaps it may be this fuel pressure damper for all we know. Perhaps that silver colored thing is just a cover over the damper. Just check it to make sure. Good luck, Tommy.

 

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Look what I found!

This confuses me more. This is what I just found. This cover looks just like the one you have on your fuel line. It is listed as a Fuel Pressure Regulator Cover. This really makes things harder to figure out. Perhaps someone can shed some light on this matter. Good luck, Tommy.

 

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1998 GT Mustang 4.6 fuel pressure regulator removal and installation instructions!

I found this info on AutoZone. Hope it helps! Some of the HTTP links may not be helpful. But most of them are! Good luck, Tommy.

This is for a 1998 GT Mustang with a 4.6 engine.

Fuel Pressure Regulator










REMOVAL & INSTALLATION






See Figures 1 through 8
  1. Depressurize the fuel system; remove shielding as needed.
  2. Remove the vacuum line at the pressure regulator.




Fig. Fig. 1: The fuel pressure regulator and the fuel pressure relief valve are both mounted on the fuel injection supply manifold-3.8L engine shown; other engines are similar





Fig. Fig. 2: Cutaway view of a common fuel pressure regulator, showing the interior working components



  1. Remove the Allen® head retaining screws from the regulator housing.
  2. Remove the pressure regulator assembly, gasket and O-ring. Discard the gasket and check the O-ring for signs of cracks or deterioration.




Fig. Fig. 3: To remove the pressure regulator, label and detach the vacuum hose from it ...





Fig. Fig. 4: ... then loosen the Allen® head screws





Fig. Fig. 5: The 5.0L engine's fuel pressure regulator is held to the fuel rail by three screws





Fig. Fig. 6: Separate the regulator from the fuel supply manifold




To install:
  1. Clean the gasket mating surfaces. If scraping is necessary, be careful not to damage the fuel pressure regulator or supply line gasket mating surfaces.




Fig. Fig. 7: Inspect the gasket for damage and replace as necessary





Fig. Fig. 8: Replace the O-rings if there is any sign of damage



  1. Lubricate the pressure regulator O-ring with light engine oil. Do not use silicone grease; it will clog the injectors.
  2. Install the O-ring and a new gasket on the pressure regulator.
  3. Install the pressure regulator on the fuel manifold and tighten the retaining screws to 27-40 inch lbs. (3-4 Nm).
  4. Install the vacuum line at the pressure regulator.
  5. Build fuel pressure in the system by turning the ignition ON and OFF (without starting the engine) at least five times. Leave the ignition ON at least 5 seconds each time. Check for fuel leaks.

 
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