How to test Fuel Pressure Regulator

93 LX

Founding Member

Jun 2, 2000

3,081

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0

Norwalk, CA.

Sep 15, 2007

#1

• Sep 15, 2007

• #1

My engine runs rich and will flood. I have vacuum when running at 25hgs. That seems high to me. Anyway the FPR holds vacuum butI wonder if it is working. Anyway to test this?

Allen

 

BigHairyMonkey

Founding Member

Jun 18, 2003

411

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Houston (Bellaire) TX

Sep 15, 2007

#2

• Sep 15, 2007

• #2

i always heard that if you pull the vac line off the FPR and if you smell it and it smells like gas then the FPR is leaking. (could be one of those myths though)

 

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HISSIN50

"How long does it take to get help in here?

15 Year Member

Nov 29, 1999

31,179

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129

Sep 15, 2007

#3

• Sep 15, 2007

• #3

93 LX said:

My engine runs rich and will flood. I have vacuum when running at 25hgs. That seems high to me. Anyway the FPR holds vacuum butI wonder if it is working. Anyway to test this?

Allen

Click to expand...

What do you mean about having vacuum when running "25hgs"? The only time you would not have any discernable vacuum is at WOT, when your reading should be near zero.

That relationship is how the FPR works. As the vacuum signal to it diminishes (as you open the throttle further), it ramps up the pressure.

If your fuel pressure is over 30 PSI at idle and around 38 PSI at WOT, you should be ok.

I'd start pulling codes and go from there. If you post a sig, that will help.

Good luck.

 

93 LX

Founding Member

Jun 2, 2000

3,081

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Norwalk, CA.

Sep 16, 2007

#4

• Sep 16, 2007

• #4

at idle i have 25 hgs of vacuum.

Yeah well i have posted codes. My other thread 86 SD 5.0L problems. has gotten nothing towards results.

When I pull the vacuum li ne on the fpr it doenst run any richer or any worse. I am thinking maybe its stuck open and allowing fuel to dump into the injectors allowing it to run rich and to the point of flooding.

Allen

Allen

 

cjones

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Jul 20, 2002

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Avondale, AZ

Sep 16, 2007

#5

• Sep 16, 2007

• #5

you'll need to hook a fuel pressure gauge to verify it. KOEO 35-45 PSI, Engine running 27-37, engine running vac hose off 40-45.

Hissin, it's on a 86 5.0 w/ Speed Density

 

vristang

15 Year Member

Mar 31, 2005

4,933

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124

Seattle

Sep 16, 2007

#6

• Sep 16, 2007

• #6

throw a pressure gauge on the fuel rail and see what the pressure is.

That's the only way to know...


jason


EDIT:
Allen,
Please, do create a sig with your major modifications listed in it.

 

93 LX

Founding Member

Jun 2, 2000

3,081

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Norwalk, CA.

Sep 22, 2007

#7

• Sep 22, 2007

• #7

no mods a completely untouched 86 Stang.

 

cjones

Founding Member

Jul 20, 2002

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Avondale, AZ

Sep 22, 2007

#8

• Sep 22, 2007

• #8

have you had a chance to check the fuel pressure yet??

 

CRASH7772

Member

Apr 27, 2003

401

1

16

NH

Sep 22, 2007

#9

• Sep 22, 2007

• #9

I know mine was running rich so I bought a Kirban FPR and liquid filled gauge for under $100. I put the gauge on first and found out my stock FPR was running @41psi. I put the Kirban and set it to 38PSI, I picked up a little acceleration and MPG's went up about 4-5. I was SD at the time as well.

 

93 LX

Founding Member

Jun 2, 2000

3,081

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Norwalk, CA.

Sep 22, 2007

#10

• Sep 22, 2007

• #10

Was that at idle? Mine is really rich. No KOEO codes. Cant get KOER codes do to rinnung so rich the engine will not idle wihtout disconnecting the BAP sensor.

Allen

 

CRASH7772

Member

Apr 27, 2003

401

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NH

Sep 22, 2007

#11

• Sep 22, 2007

• #11

Was at idle but with vacuum line removed. And I didn't pull any codes either.

 

cjones

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Jul 20, 2002

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Avondale, AZ

Sep 23, 2007

#12

• Sep 23, 2007

• #12

Allen,
this is for the 86 GT Speed Density car, right?? if so, you need to hook a intake vacuum hose to the BAP sensor and make it a MAP sensor.

 

93 LX

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Jun 2, 2000

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Norwalk, CA.

Sep 23, 2007

#13

• Sep 23, 2007

• #13

it is all hooked up. When I plug in the BAP electronicly is when the the engine will not idle. The car is a 86 LX 5.0L HO Auto Speed Density car. Plugs are black. I remove the vacuum line going to the charcoal canister the engine will lean up but the idle is way high. I just can not figure out why its dumping fuel with engine vacuum at 25 hgs and no other codes other then BAP when the ening is running. I am really thinking of dumping the car. I do want to restore it for my daughter, her graduation present when she graduates college but I figure it may be easier to get a different car.

Allen

 

S

sands9330014

Member

Sep 28, 2024

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japan

Sep 28, 2024

#14

• Sep 28, 2024

• #14

93 LX said:

it is all hooked up. When I plug in the BAP electronicly is when the the engine will not idle. The car is a 86 LX 5.0L HO Auto Speed Density car. Plugs are black. I remove the vacuum line going to the charcoal canister the engine will lean up but the idle is way high. I just can not figure out why its dumping fuel with engine vacuum at 25 hgs and no other codes other then BAP when the ening is running. I am really thinking of dumping the car. I do want to restore it for my daughter, her graduation present when she graduates college but I figure it may be easier to get a different car.

Allen

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Did you find the answer? I'm in the same situation please help.