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Author
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Topic: 68 Mustang: Fluctuating fuel pressure & idle
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silverLX
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Member # 3207
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posted
 
 
I just got my friends 68 mustang going, it has an 88 5.0 motor and a Tremec 3550. It has MSD coil, box, and distributor. It has a Holley blue pump with regulator set to 6psi. I set the idle to 800rpm and test drove it. After 5 minutes of driving the idle went to 500rpm and 4 psi on the fuel pressure guage, so I put them back up and it did the same thing again....ANY ideas?? EVERYTHING is new, so could something be defective?
thanks
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88LX hatch 410w
88LX vert gears, exhaust
95GT H/C/I
Posts: 1613 | From: Sonoma County | Registered: Aug 2003
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PunkINa5.SLOW
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Member # 10
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posted
If it has been sitting awhile could be debris
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OUTTA THA DRAMA
R.I.P. MIKE STARKEY MY BABY BROTHER
12/8/77-5/17/03
Posts: 2495 | From: MTZ | Registered: Sep 2000
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Fostang
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Member # 3752
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posted
umm? what kind of carb? what does it have? 800 rpm why(I can see why if you have major performance parts)
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67' Fastback TT 408
67' Camaro Lsx
64' Corvette Fuelie
57' Chevy Bel Air Lsx
68’ Pony Convertible
66’ Pony Coupe
Posts: 3011 | From: Stockton/Danville | Registered: Nov 2003
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silverLX
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Member # 3207
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posted
i dont know why 800rpm, it will idle lower no problem. it has been sitting for 3 months. Any other ideas?
thanks
Posts: 1613 | From: Sonoma County | Registered: Aug 2003
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Fostang
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Member # 3752
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posted
I would idle mine at 550 rpm with edel carb, perfomer intake, performer cam, timing at 12, full advance 36, fuel pressure at 5.5 psi, (edelbrocks are not ment for more than 5.5 psi.)
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67' Fastback TT 408
67' Camaro Lsx
64' Corvette Fuelie
57' Chevy Bel Air Lsx
68’ Pony Convertible
66’ Pony Coupe
Posts: 3011 | From: Stockton/Danville | Registered: Nov 2003
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silverLX
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Member # 3207
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posted
I set the fuel pressure to 5 psi, but cant set the idle lower then 700 or the motor shakes too much because of the cam. Thats beside the point though, why does the fuel pressure keep on going up and down on its own?? this morning it was down to 2 psi, we set it to 5 and now its up to 6.5?? Please help any way you can!!
thanks
Posts: 1613 | From: Sonoma County | Registered: Aug 2003
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PunkINa5.SLOW
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Member # 10
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posted
Dude you probably have debris in the fuel lines.
IF not that then make sure the voltage is not fluctuating to the power lead on the fuel pump itself.
Holley blue pumps along with their regulators are usually pretty sturdy
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OUTTA THA DRAMA
R.I.P. MIKE STARKEY MY BABY BROTHER
12/8/77-5/17/03
Posts: 2495 | From: MTZ | Registered: Sep 2000
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