09-09-2019, 06:19 AM
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#1
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Fuel reassure Test
Hi all, 99 Boxster Base. P1123...P1125 CEL's
Did fuel pressure test and results are:
Engine Off 3.3Bar
Idle: 3.1 Bar
Question, with engine off (after running and shut down) the fuel pressure was 2.6 Bars if I let it sit... it crept up to 3.4 Bars...... which is the accurate reading?
Also....when replacing the fuel rail cap on the schrader valve I over torqued it with my cheapo torque wrench and popped the top of the cap and scored the top of the fuel rail with the bottom of the cap totally trashing the cap. Is this an issue I have to worry about. The valve seemed good and didn't leak...only a slight score or scratch at the base. Can I just replace the cap and move on. Thanks V
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09-09-2019, 06:57 AM
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#2
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The higher reading.
Nominal values should be 3.8 bar +/- 0.2 engine off, 3.3+/-0.2 idling
You need to replace the brass cap.
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“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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09-09-2019, 10:03 AM
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#3
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Thanks for the reply JFP ...OK...so I'm low and out of range at 3.4 with engine off and low at 3.1 but with in range at idle. Is this okay or does the fuel pressure regulator need to be replaced to remedy the 1123....1125 codes??
I ordered the new cap already...as I said I scored/scratched the base of the schrader valve by over torquing, it seems the brass cap is designed to strip before doing any damage to the rail..it doesn't leak ....am I good with just replacing the cap.
Thanks V
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09-09-2019, 10:28 AM
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#4
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Quote:
Originally Posted by Vza
Thanks for the reply JFP ...OK...so I'm low and out of range at 3.4 with engine off and low at 3.1 but with in range at idle. Is this okay or does the fuel pressure regulator need to be replaced to remedy the 1123....1125 codes??
I ordered the new cap already...as I said I scored/scratched the base of the schrader valve by over torquing, it seems the brass cap is designed to strip before doing any damage to the rail..it doesn't leak ....am I good with just replacing the cap.
Thanks V
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Have you completed the vacuum test of the regulator, and did it pass?
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“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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09-09-2019, 12:11 PM
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#5
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OK....Thats new to me....read only to check fuel pressure. Will move on to vacuum testing regulator. BTW are my fuel # ok? No worries about the scored fuel rail?? I didn't see a vacuum test for the regulator in the shop man is it in the Bentley book??
Last edited by Vza; 09-09-2019 at 12:20 PM.
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09-09-2019, 01:45 PM
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#6
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Quote:
Originally Posted by Vza
OK....Thats new to me....read only to check fuel pressure. Will move on to vacuum testing regulator. BTW are my fuel # ok? No worries about the scored fuel rail?? I didn't see a vacuum test for the regulator in the shop man is it in the Bentley book??
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No, but it is in the Porsche OBD II code diagnostics manual for the car.
One pressure is a bit low.
If the rail isn't leaking, it should be fine.
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“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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09-09-2019, 06:43 PM
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#7
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Well I don't have access to the OBD manual. Can anyone point me to instructions on doing a vacuum test on fuel pressure regulator. Couldn't find anything. V
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09-10-2019, 01:24 AM
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#8
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Quote:
Originally Posted by Vza
Well I don't have access to the OBD manual. Can anyone point me to instructions on doing a vacuum test on fuel pressure regulator. Couldn't find anything. V
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Ummmmmmmmmmmmmm......Put a tee in the vacuum line at the regulator, hook up a vacuum gauge, start car and let idle, read gauge............... 
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“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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09-10-2019, 06:47 AM
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#9
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I figured you'd know. So I'm measuring vacuum being pulled from FPR correct? Thanks V
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09-10-2019, 08:16 AM
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#10
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Quote:
Originally Posted by Vza
I figured you'd know. So I'm measuring vacuum being pulled from FPR correct? Thanks V
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Yes, if the vacuum to the regulator is restricted, it will alter how the regulator works.
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“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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09-10-2019, 12:41 PM
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#11
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I did the test and got 18.5 in/hg of vacuum. Seems thats correct considering thats what it measured right from the vacuum hose as well. So it seems there are no restrictions. No gas coming from FPR at idle with hose disconnected. Any other thoughts for the 1123 1125 codes. It seems only to come up if I accidentally get close to stalling the car w the clutch or I rev high briefly getting into gear. Although the code is still pending shortly after reset. V
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09-10-2019, 04:52 PM
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#12
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Quote:
Originally Posted by Vza
I did the test and got 18.5 in/hg of vacuum. Seems thats correct considering thats what it measured right from the vacuum hose as well. So it seems there are no restrictions. No gas coming from FPR at idle with hose disconnected. Any other thoughts for the 1123 1125 codes. It seems only to come up if I accidentally get close to stalling the car w the clutch or I rev high briefly getting into gear. Although the code is still pending shortly after reset. V
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Have you done an intake vacuum test????
If you get 18.5 in of vacuum that is within spec but on the low end.
I had a minor vacuum leak on my 2000S and still pulled 19.
If you have a vacuum leak it could contribute to your codes.
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09-11-2019, 10:59 AM
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#13
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What is the spec for Vacuum?
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09-11-2019, 11:11 AM
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#14
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Quote:
Originally Posted by Vza
What is the spec for Vacuum?
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0.4-0.6 Bar
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“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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09-11-2019, 11:20 AM
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#15
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So I'm at .63 Bar ....so I'm on the high side. Is that acceptable? V
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09-11-2019, 11:23 AM
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#16
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Quote:
Originally Posted by Vza
What is the spec for Vacuum?
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if your asking for the vacuum spec. at the intake it is 18-22 in/gh of vacuum preferably with a steady needle.
At engine idle
Last edited by blue62; 09-11-2019 at 11:30 AM.
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09-11-2019, 11:33 AM
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#17
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Ok...well I have two specs going here !! 0.4-0.6 Bar and 18-22 in/hg I'm on the high side of 1 and low side of the other.
Last edited by Vza; 09-11-2019 at 11:36 AM.
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09-11-2019, 11:47 AM
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#18
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sorry not meaning to create confusion.
I would say your reading is fine
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09-11-2019, 11:58 AM
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#19
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Thats fine thanks V
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09-11-2019, 06:06 PM
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#20
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I don't know maybe its a quirky thing with the codes. I drove at length before they showed up. No pending codes now... I guess I'll see what happens. My oil filler cap checks out good and I sprayed some carb cleaner around the small hoses coming off the vac tank,plenum hoses etc...no change in engine note.Thoughts?? V
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