NO FUEL PRESSURE WTF???

93 teal terror

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Jul 13, 2001

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Durham N.C.

Mar 12, 2004

#1

• Mar 12, 2004

• #1

WTF? I went to move my car to wash it and it ran like crap. I just put a new kirban AFPR on it and it was running awesome..passed emissions and everythnig. So after im done washing it i go and hook up the fuel pressure guage and it reads 24 psi????? I set it at 39 with vaccum off and 30 with it on. It doesnt make a difference if i turn the adjustment on the regulator or unplug the vaccum it just reads 24psi. I cant see any leaks and i have good vaccum pressure. What gives????

 

mustangdaren

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Hildebran, North Carolina

Mar 12, 2004

#2

• Mar 12, 2004

• #2

I would check your fuel filter first but it sounds like you got a defective regulator

 

93 teal terror

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Jul 13, 2001

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Durham N.C.

Mar 12, 2004

#3

• Mar 12, 2004

• #3

I just put a brand new filter on 2 days ago. The place I bought it form said that wouldnt take it back unless the diaphragm was broken. The only way to test that is to see if it holds vaccum. Then he says but you probably dont have access to something like that....so now what?? what the hell

 

Mike86Stang

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Apr 11, 2000

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Red Lion, PA

Mar 12, 2004

#4

• Mar 12, 2004

• #4

Put back on your stocker... if your back at the regular FP then you know it's the FPR

 

93 teal terror

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Durham N.C.

Mar 12, 2004

#5

• Mar 12, 2004

• #5

Yeah I didnt think about putting the stocker back one....glad i didnt throw it away. I had to drill out a fitting that broke off where the schredar valve is so it may have got some shavings in there and clogged something. where would these shavings go if they were to clog something?

 

jrichker

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#6

• Mar 12, 2004

• #6

With the vacuum line off, engine running, you should see at least 39 PSI, or be able to turn it up to 39 PSI. Capping the engine side of the vacuum line when you do the test is an option, but it won't change the pressure if you don't do it.

No 39 PSI:
1.) Fuel filter bad
2.) Regulator defective
3.) Fuel pump weak
4.) Fuel line damaged or obstructed
5.) Fuel pump relay or wiring bad, causing fuel pump to have low output.


A Mytie Vac hand vacuum tester can be used to check out the regulator for vacuum leaks. They cost $25-$40, depending on if they are all metal or plastic and if they are on sale. I don't think that vacuum is the source of your problem though

 

Mike86Stang

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#7

• Mar 12, 2004

• #7

your injectors

 

93 teal terror

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#8

• Mar 12, 2004

• #8

Well thats just super
Is there anyway to check my injectors?

 

93 teal terror

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#9

• Mar 12, 2004

• #9

another thing to add....when i turn the key forward and try to prime the system 3 or 4 times it still only reads 5psi or so. Before when i primed it i could get it up to 40 psi.

 

jrichker

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#10

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Right now I don't think an injector stuck open is your problem. That is the only way it could cause fuel pressure to drop.

A more likely case is chips from your machine work lodged in the regulator valve seat.

Here's a way to test for leaking injectors: Connect a rubber hose to the injector where the fuel rail would normally connect and apply compressed air to the rubber hose. I hook the whole thing up, apply compressed air to the injector and stick it in a paper cup of soapy water. If the injector leaks, it makes bubbles. Cheap if you have the stuff laying around, and works good too.

 

Mike86Stang

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#11

• Mar 12, 2004

• #11

I think your regulator is beat....or possibly if that shrader was re tapped then maybe somehow your guage isn't reading properly

 

93 teal terror

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#12

• Mar 12, 2004

• #12

I think it is the regualtor, b/c i can hear air in the fuel rails and it still runs, just crappy b/c the pressure is low. If the diapragm was broken it would allow air to pass through it right? Has anyone had this happen? The regulator is only a day old. I would think though that it something clogged it up then it wouldnt have run so well for so long. I put like 30 miles on it beating the crap out of it. Im putting the stock one back on to see if that helps. Can you take the regulator apart by removing the allen bolts around it? Will I screw anything up doing this to see if somethings clogging it or if the diaphragm is broken?

 

jrichker

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#13

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Some explanation of how the system works is in order here...

The fuel pressure regulator is a shunt style regulator, as opposed to the series style regulator most of us are familiar with.

A shunt regulator directs the excess pressure back to the tank via the return line. The shunt regulator is parallel to the injectors. By decreasing the amount the regulator opens, the pressure increases. As the regulator opening increases, the flow back to the tank increases and the pressure drops. When dirt or debris get trapped in the regulator valve seat, they hold the regulator open and the pressure drops. The dirt or debris prevent the regulator from holding the requested pressure setting.

 

93 teal terror

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#14

• Mar 12, 2004

• #14

jrichker said:

Some explanation of how the system works is in order here...

The fuel pressure regulator is a shunt style regulator, as opposed to the series style regulator most of us are familiar with.

A shunt regulator directs the excess pressure back to the tank via the return line. The shunt regulator is parallel to the injectors. By decreasing the amount the regulator opens, the pressure increases. As the regulator opening increases, the flow back to the tank increases and the pressure drops. When dirt or debris get trapped in the regulator valve seat, they hold the regulator open and the pressure drops. The dirt or debris prevent the regulator from holding the requested pressure setting.

Click to expand...

Thanks, that clears things up....It is the regulator, the stock one works fine and holds 40psi priming. Can I open up the AFPR and get the debris out of there is any? Will I mess the unit up this way? Thanks