1998 mustang gt fuel pump / pressure issues - Ford Mustang Forum
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post #1 of 16 (permalink) Old 12-26-2009 Thread Starter
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1998 mustang gt fuel pump / pressure issues

Hello,

I am trying to help my sister with her 98 GT, 100,458 miles. I am looking for some input on the pretty consistant starting issues it is having.

1st thing in the AM, starts up ok. Drive it anywhere, even short distances, then it will not re start (engine just turns over). Sometimes it would start after sitting awhile. To date it has only died while running 2x.

I suspect it is fuel related. Here are some additional symptoms I noticed.

I don't see much fuel pressure, I press the Schrader valve on the fuel manifold and there is never anything there. The only time anything came out was when I pressed it while the engine was running (fuel of course came out).

I checked for voltage at the wiring at the back of the gas tank, looks good.

I sat under the car and had my sister turn on the ignition 5 times, I heard the fuel pump prime each time, wouldn't start after priming. Had her try again and quickly crank it over before the priming ended and it started.

Let it run a minute or two and then just turned the ignition on and the pump did not prime anymore.

I searched and read what I could find here and in other places, based upon that and the symptoms I noticed, I suspect the fuel pump is only working intermittantly.

Is that probably it or is there anything else to check like a clogged return line?

Thanks for reading.

Mark
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post #2 of 16 (permalink) Old 12-26-2009
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You could have issues with a lot of things, for starters. Try to get a pressure gauge and measure the fuel pressure at the rail.

At idle, the fuel pressure should be about 32psi.

Remove & plug the vacuum port hose to the fuel pressure regulator, it should jump to about 40 psi.

If you can't get that pressure, you could have a bad pressure regulator, fuel pump or other issue.
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post #3 of 16 (permalink) Old 12-26-2009
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I GOT THIS!!!!!

There is a module on the inside of the passengers front fender, EECU of some sort. Controls the fuel pump, as well as other assorted things such as AC. THAT IS THE PROBLEM- JUST happened to me. I bet you at least 50% if not more of my posts on here that thats what it is!

1997 Mustang GT- DOHC, Termec T-45, LT Headers, Bassani O/R X, Tri-ax, 3.73s, JLT CAI, BAMA tune

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post #4 of 16 (permalink) Old 12-26-2009
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I GOT THIS!!!!!

There is a module on the inside of the passengers front fender, EECU of some sort. Controls the fuel pump, as well as other assorted things such as AC. THAT IS THE PROBLEM- JUST happened to me. I bet you at least 50% if not more of my posts on here that thats what it is!
The CCRM (constant control relay module), could definitely cause the issue, I wonder if the 1998 GT has the fuel pump module in the driver's side trunk like my 2000 GT has. If not that my only be on returnless fuel system cars.
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post #5 of 16 (permalink) Old 12-27-2009
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No, it sure does. Yeah the EECU isn't what its called it is the CCRM (brainfart). It is indeed located on our cars under the passengers side front fender. the inertia switch is what you are referring to that is mounted on the drivers side trunk inner

1997 Mustang GT- DOHC, Termec T-45, LT Headers, Bassani O/R X, Tri-ax, 3.73s, JLT CAI, BAMA tune

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post #6 of 16 (permalink) Old 12-27-2009
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the inertia switch is what you are referring to that is mounted on the drivers side trunk inner
The module I am referring to is on the driver's side fender well about 1-2 ft in front of the inertia switch.

It is where my Kenne Bell BAP is mounted.
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post #7 of 16 (permalink) Old 10-13-2010
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Exclamation Same problem....

I'm experiencing pretty much the same problem with my 98.. At idle theres 30 psi pressure at the rail, as soon as you turn the car off it immediately drops to 0. turning the switch on multiple times doesn't not have any affect still shows 0 until the car is actually running. It will never crank the first time i get in it, has to be turned over for a few seconds then stop and do it again and it fires up fine. I thought maybe the fuel pressure regulator was dumping the fuel back into the tank but blocking the return line has no effect when turning the key off it still drops to 0. The pressure does go up to 40 psi when you unplug the vacum line, and there is plenty of vacum on the vacum line. So is it possible my fuel pump is going bad and not keeping the system pressurized so when you first crank the engine it fires up or ???? Any thoughts or help would be greatly appreciated....:?::?::?::?:
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post #8 of 16 (permalink) Old 10-13-2010
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I'm experiencing pretty much the same problem with my 98.. At idle theres 30 psi pressure at the rail, as soon as you turn the car off it immediately drops to 0. turning the switch on multiple times doesn't not have any affect still shows 0 until the car is actually running. It will never crank the first time i get in it, has to be turned over for a few seconds then stop and do it again and it fires up fine. I thought maybe the fuel pressure regulator was dumping the fuel back into the tank but blocking the return line has no effect when turning the key off it still drops to 0. The pressure does go up to 40 psi when you unplug the vacum line, and there is plenty of vacum on the vacum line. So is it possible my fuel pump is going bad and not keeping the system pressurized so when you first crank the engine it fires up or ???? Any thoughts or help would be greatly appreciated....:?::?::?::?:
For the fuel pressure to quickly drop to zero means either a bad fuel pressure regulator, bad fuel pump check valve or a leaky fuel injector(s).

Unless you have done th PPRV delete mod. If so, there isn't a check valve in the fuel pump since the mod removes it.

2003 GT Convertible (sold & missed)
2000 GT coupe (Craigslist project. Fixed. Now my DD). Windsor to Romeo swap.
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post #9 of 16 (permalink) Old 10-13-2010
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No leaky injectors, what is the PPRV delete? where is the fuel pump check valve?? I am currently in the process of putting a new pump in praying this will solve my prob... thanks
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also on my car the FPR appears to be built into the passenger side fuel rail..... How would one change that if it were the problem aside from going to a junkyard or the dreaded $$Ford$$ lol
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No leaky injectors, what is the PPRV delete? where is the fuel pump check valve?? I am currently in the process of putting a new pump in praying this will solve my prob... thanks
How do you "KNOW" the injectors are not leaking? Are you expecting them to leak outside the engine? That is not where they leak from.

A leaky injector leaks from the tip. A few drops of fuel will drip into the intake manifold where it can't be seen.

The check valve is located inside the fuel pump basket. It's purpose is to maintain fuel pressure during shut down.

If you don't know what a PPRV delete is and/or haven't made any mods to the fuel system, then most likely the mod has not been done.

If you are currently replacing the fuel pump, then isn't further discussion a little late? At this point wouldn't make more sense to re-test after the fuel pump has been replaced?

Please post a picture of your engine bay. I don't think the part that is "built in" to the fuel rails is what you think it is.

Good luck.

2003 GT Convertible (sold & missed)
2000 GT coupe (Craigslist project. Fixed. Now my DD). Windsor to Romeo swap.
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Oh ok, didn't know that you were refering to them leaking internally thought you meant around the o rings sorry.. Will get a pic of my fuel rail uploaded tomorrow so we can figure that out... thanks for all of your help thus far
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If it were leaky injectors would that be probable cause for the rail pressure to drop 0 upon turning off the key?? Can you tell me more about the check valve you refered to earlier besides it being in the fuel pump basket?? Is it part of the float assembly or the pump itself or????
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If a leaky injector couldn't cause the problem, why would I mention it? There is a procedure in the Ford service manual where the rails are removed and pressurized and the injectors tested for leaks.

If you want to know for certain, send the injectors out for cleaning and flow testing. Try injectorrx.com. Once cleaned and flow tested, as good as new. Cheaper than new.

I don't now exactly where the check valve is. However, if the fuel pump assembly is replaced, the check valve is part of the assembly. If you want to know for yourself, research the PPRV delete as the FP check valve is one of the things this mod removes.

As said before, fuel pressure leak down could also be the regulator.

Look, this is a process that takes steps to narrow down. NO ONE out in Internet land can tell you which of the ump-teen possibilities is what is actually what is wrong with your car. At best it's educated guesses.

Additional testing and information can improve the results.

IMO, the odds do favor it being a fuel pump esp considering the age of the car (98).

2003 GT Convertible (sold & missed)
2000 GT coupe (Craigslist project. Fixed. Now my DD). Windsor to Romeo swap.
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Got the new fuel pump installed and i think it may have solved my problem, the pump that was in it was a walbro, usure of specs., but looked a lot different then what i replaced it with from airtex. After researching on the web i think the pump that was on it was for a returnless system which may possibly be why i had the symptoms i had ??? Another joy of buying a used car, never knowing what had been put on it prior... True test will be in the morning when I get up to go to work.... Will post results of start try later tomorrow, thanks for all of your help wmburns
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