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Old 10-03-2013, 08:27 AM   #1
TheEvilBain_TDB
 
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Default 2002 Mustang Gt New Fuel Pump Bad Check Valve? Pressure leak down.

I've had issues with fuel pressure leak down on my 02 Gt. After sitting for a year I just replaced the clutch and had to get a new key programed since my wonderful wife lost the key off her chain (only one we had) i towed it to ford and had them make me 2 new ones after replacing my ignition tumbler my self. I guess my fuel pump went out as the tech went to pull the car out. I replaced the fuel pump and it seemed to do ok for a week. Now I have to cycle the key 4 times to prime the pump to get it up to pressure. I hear the pump alot louder then my stock one. so do you think I got a lemon pump with a bad check valve serves me right for going eBay :-/ or could it be my IAC and egr plate mod (had hanging idle) I'm lost no fuel leaks runs great after she starts hate to buy a new pump but looks I might be going that way. Thank you guys
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Old 10-05-2013, 01:38 AM   #2
petrock
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There can be any number of reasons for the symptoms your having. It could be a leaky fuel injector, fuel line connector, fuel line, check valve, or weak fuel pump or crimped/clogged/damaged fuel line. The only way to know is to do a leak down test with a fuel pressure gauge and a pair of vise grips. You can rent the gauge from your local auto parts store. There are a bunch of video’s on YouTube on how to do this. But the basic gist is to attach the gauge to the Schrader valve on the fuel rail, put the key in the ON position (don’t start the car), wait for the fuel pump to shut off and watch the gauge. If the pressure drops within about 15 minutes or so then you have a leak somewhere in the fuel system. If the pressure doesn’t reach the normal fuel level then you have a weak fuel pump. You can track down the leak by divide and concur diagnostics by running the same pressure test as before, but before turning the key off take a pair of vise grips (with rubber hose covering the teeth) clamp down on the flexible fuel lines then shut the key off. If it continues to leak the leak is between the clamps and the fuel injectors. If it stops leaking the leak is between the clamps and the fuel pump. Keep working in which ever direction the leak is until you get a different result and the leak will be between those two points. Hope that helps… Good luck...
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Old 10-05-2013, 06:47 AM   #3
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How old is the fuel filter?
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Old 10-06-2013, 08:13 AM   #4
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Thank you for the responses The filter is new. I'm going to get a fuel pressure gauge this week. I've noticed it dosnt do it unless I let it sit for a few days. But of I start it up daily no issues. There isn't any leaks at the the injectors I checked that. Ill let you guys know after I check my fuel pressure and post my findings. Thanks again for the help guys :-)
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Old 10-08-2013, 02:05 AM   #5
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Quote:
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There isn't any leaks at the the injectors
the leak may not be on the outside of the motor. The leak could be leaking into the combustion chamber. That is one of the most common type of injector leak, second to the rubber o-rings at the top/bottom of the injector.
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Old 10-08-2013, 08:31 PM   #6
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It's very possible you have a pressure leak inside the tank. The orange seal from the plastic fuel pump case (for lack of a better word) can tear causing a pressure leak that you won't see until you pull the tank back down. Unfortunately that is an expensive fix unless you can find one someone else has as Ford only sells the whole unit. Or maybe you just put it in there wrong and didn't tighten the hose clamps tight enough.

An injector leaking down that bad would normally present some other driveability symptoms since it would have to hang just about wide open constantly in order to leak down that much.

There aren't any fuel lines you should be vise gripping hard enough to shut off fuel flow. There really aren't any fuel lines you should be vise gripping period. Plus if there are external leaks of the degree you are talking about you would see and smell the fuel. My money is on a leak inside the tank.

I've said this many times and it is a lesson I had to learn myself over time. If you perform a repair and something is amiss after you're done. It's usually you're fault. Good luck with your issue.
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Old 10-09-2013, 04:10 AM   #7
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An injector leaking down that bad would normally present some other driveability symptoms since it would have to hang just about wide open constantly in order to leak down that much.
Thats not entirely accurate. As the OP stated, the problem happens when he leaves the car for a couple days. An injector that drips is enough to cause this problem. The fuel pressure will bleed down gradually as the OP describes. There would be no drivability problems in that case.


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There aren't any fuel lines you should be vise gripping hard enough to shut off fuel flow. There really aren't any fuel lines you should be vise gripping period.
There are a bunch of flexible fuel lines that can be pinched throughout the fuel system. For example, the lines going to/from the fuel filter, or the lines going to the fuel rail. Pinching a flexible/rubber fuel/brake/vacuum line is perfectly fine as long as you don’t clamp down so hard to damage the line. It only takes a little bit of pressure to pinch off the line. If you cover the teeth of the clamps with a bit of scrap hose you’ll be just fine. I’ve done it a ton of times over the years on various cars I’ve owned with no adverse effects.


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Originally Posted by Stevo86 View Post
Plus if there are external leaks of the degree you are talking about you would see and smell the fuel.
Also not accurate. The OP’s leak is probably fairly small since it takes a few days to leak down enough to cause the problem he is seeing. Unless your crawling around underneath the car, looking for wet spots, you might smell it if the wind is right. But chances are, with that small a leak, you won’t. If its a large enough leak to leave a puddle or something, then yeah you would be able to smell it pretty easily.


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I've said this many times and it is a lesson I had to learn myself over time. If you perform a repair and something is amiss after you're done. It's usually you're fault. Good luck with your issue.
I completely agree… :-)
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Last edited by petrock; 10-09-2013 at 04:12 AM.
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Old 10-09-2013, 06:09 AM   #8
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I missed the part about the gradual leak down. Either way it's the part about the 4 times to prime that leads me to believe if it is a leak it's a large one. It also re-affirms my suspicion that it is in the tank.

So #1 yes you're right a hanging injector could cause a gradual drop in pressure, but not a big enough leak to require the pump to prime multiple times without you noticing it.

#2 There are only a few "flexible" fuel lines on a mustang gt. Some of them have plastic inserts inside the line. Vise grip the plastic piece and you broke your fuel line.

#3 Once again four times to prime is the reason I'm saying there must be a large leak. If it were that big on the outside of the car you would smell it/ see it. I've had large leaks from a rolled up injector o-ring that you could see and smell and the car still primed and fired up first try. Anything that requires you to cycle the key four times is BIG.
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Old 10-09-2013, 10:44 AM   #9
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Thanks guys after removing the tank again re cleaning it double checking all the lines and re fitting them I found that the out put feed nipple (so to speak) had a pin hole so its a manufacture error due to its apart of the fuel pump. The only reason I found the issue is Is while running and under the rear of the car with my tank lowerd a bit it lightly squirted from a pin hole. Have no idea how that even happens lol but I ordered a new pump :-/ thanks again for all your help
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Old 10-09-2013, 12:01 PM   #10
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I love it when I'm right lol glad you got it worked out man.
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Old 10-09-2013, 12:01 PM
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