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Old 08-24-2005, 01:02 AM   #1
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What happens when a Fuel Pressure Regulator Goes bad

in the 87-92's?

does it dump too much fuel? not enough? is there even a default mode?

My car is sputtering under part throttle in every gear... seems okay at WOT, but im using 25 miles per QUARTER TANK... my eyes are burning...

I do not have a fuel pressure gauge, but im thinking it's too high. Any input?
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Old 08-24-2005, 01:14 AM   #2
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Aftermarket? I had an aftermarket unit (different than stock style) go bad, and the diaphram got eaten up by fuel, and allow fuel to be forced out of the vac line.
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Old 08-24-2005, 02:39 AM   #3
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no it's stock.

And Im pretty damn sure it's running rich, I can't drive the car without literally crying.
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Old 08-24-2005, 02:54 AM   #4
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what year is your car? if it's a speed density car, check the vac line. my Tbird's vac hose came off of the MAP sensor and it was running pig rich. it would really only run if it was at WOT, and sputter like yours. i thought all the vac lines were good until i checked them all over again (same thing happened to my mustang, it was running lean and one of the vac hoses was disconnected, i coulda sworn they were all connected...)
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Old 08-24-2005, 10:28 AM   #5
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It depends on what happens to the regulator. If it gets stuck closed, then the fuel pressure will go through the roof and the engine will run very rich and will probably bog quite badly off idle and won't pass emissions. On a N/A car, it will probably run like a pig across the entire powerband. On my SVO it would actually run well at WOT because the fuel pressure was about right for 15 lbs of boost. If its leaking it will probably run a little rich but nowhere near as badly as if the pressure is too high.

Speaking from experience, the best way to diagnose any kind of regulator problem is to hook up a gage and see what the pressure is at idle. When mine was stuck closed, I was getting 60+ psi at the rail!!
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Old 08-24-2005, 01:11 PM   #6
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Here's a pretty good explanation of how regulators work. It'll help you see why fuel pressure commonly shoots up when they fail:

http://fordfuelinjection.com/index.php?p=41
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Old 08-24-2005, 05:30 PM   #7
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Okay guys, thanks for the link.

If I tap the rail, will it matter that im drawing the fuel pressure before the regulator? Will the gauge still be accurate?
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Old 08-24-2005, 06:25 PM   #8
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pull the vacuum line off and crank the engine over, if its really bad it'll start shooting out the top of the regulator
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Old 08-24-2005, 11:53 PM   #9
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fuel reg

my stock stock one got stuck on same symptoms you have
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