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5.0 fuel pressure regulator questions

itsabronco

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Jul 27, 2009
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551
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Banning, CA.
-Does the regulator on a 5.0 hook up to any vacuum soarce or is there a
primary and secondary vacuum on the efi upper intake like on a carburetor?

-What does the vacuum do to the regulator such as increase/decrease pressure?
This conversion is KILLING me !:p
 

57baja

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Jan 6, 2009
Messages
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-Does the regulator on a 5.0 hook up to any vacuum soarce or is there a
primary and secondary vacuum on the efi upper intake like on a carburetor?

-What does the vacuum do to the regulator such as increase/decrease pressure?
This conversion is KILLING me !:p

There is a small metal tube behind the intake manifold, hook it up to there. If you have the manifold off flip it upside down and you'll see where is.
 
OP
OP
I

itsabronco

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Joined
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Messages
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Loc.
Banning, CA.
There is a small metal tube behind the intake manifold, hook it up to there. If you have the manifold off flip it upside down and you'll see where is.

I know what your talking about but its not there. There is only 2 fittings that are 3/8'. no small tube. Thats why im asking if there is a difference in vacuum ports on the upper intake.
 

66fora69er

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If there is not a vacuum tree screwed into the underside of the upper intake then that is what you are missing. I believe it accepts 3 vac lines
 

DirtDonk

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If not on yours, maybe an adapter of some kind? Perhaps a short length of the 3/8", necked down by one of those little plastic dealies you can buy at auto parts stores?

Just did an Explorer upper and it had the right tube already there. Kept the original vacuum line as well. that plastic tubing with rubber 90° elbows at each end. Slightly smaller on the regulator side, if I'm not mistaken.

Good luck.

Paul
 

DirtDonk

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Oh, and, as you've probably figured out from what they all said, it's full manifold vacuum all the time. The regulator can increase fuel pressure as vacuum drops. In my experience, it's typically a straight change-up though. As opposed to a gradual increase.
Depending on the engine/regulator combo, you might have 35 to 40 psi at idle, and 45 to 50 when the throttle is pressed. Something like that.
If I'm not mistaken, some setups don't simply increase pressure though. They "maintain" a given pressure at the different loads.

Paul
 

Steve83

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It maintains a constant pressure drop across the injectors of ~45psi. If manifold vacuum is high (near 0psia/-15psig at idle), the regulator keeps fuel pressure near 30psig. When the throttle opens and man.vac. comes up, the regulator brings up the fuel pressure to match. It's not off/on - it's progressive.
 

DirtDonk

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The only ones I've ever personally tested with a gauge worked like a light switch. At least according to the gauge. The V6 Mustang sat at a steady 30 at idle, then instantly jumped to a steady 40 as soon as the throttle was cracked.
The Explorer setup sits at a steady 39 at idle, then jumped instantly to a rock steady 45 when the throttle was actuated.

Are those not working properly then, or is the value different at the injectors vs at the gauge side of the regulator?

Paul
 
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itsabronco

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Jul 27, 2009
Messages
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Loc.
Banning, CA.
thanks for the input gentlemen. i am going to hook it up to vacuum, put a battery in it, and see what happens. i still need cooling system though!
 

Steve83

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The only ones I've ever personally tested with a gauge worked like a light switch. At least according to the gauge.
That's how it will behave with no load on the engine. Have you ever driven with the gauge attached? This was Saturday in Mom's MGM - I was able to make the gauge needle move proportionally to the gas pedal:

i still need cooling system though!
You can run it dry for ~1 minute. I did that on Frank's engine before we bought it in the JY so we could check compression.

 
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