I was just thinking about my high fuel pressure and may of figured it out.
05-22-2002, 03:13 PM
#1
Team Owner
Thread Starter
I was just thinking about my high fuel pressure and may of figured it out.
It may be possible that I do not have a great vacuum pull on it.
See this image of the vacuum line routing.
Notice the fuel pressure regulator appears to pull it's vacuum off of the same line that the air divertor boxes for the AIR system do on the front. They branch off of a Y.
I can tell you with CERTAINTY that the vacuum connection going to the superram on the back for the air divertor boxes is not a very strong one.
You can't really see it in this picture too well.....
But you can see the flexible line that comes off of the center vacuum fitting RIGHT behind the fuel pressure sending unit. Well I have cut that line to about 8" and it makes 270* of a circle and I have stuck a "donated" portion of formed vacuum line from another area in the end of it. This then sticks into the 90* fitting on the end of the air divertor vacuum connection that used to be plugged into my stock manifold. That last connection is VERY loose. I didn't worry about it before because I thought it was just for the divertors until I thought about it again.
I am REALLY willing to bet I have a major vacuum leak right there, and that it is not pulling the pressure down as far as it shoudl be since it also supplies the vacuum for the AFPR. This may also tell me why I am getting different fuel pressure readings at full throttle. Sometimes it jumps from 37.5 while cruising to 50.5psi and last night I even saw 64.5psi a few times.
I think that a severe leak on this line would result in major fuel pressure increases. Yes or no? I will work on securing that connection immediately.
[Modified by scorp508, 3:11 PM 5/22/2002]
[Modified by scorp508, 3:14 PM 5/22/2002]
See this image of the vacuum line routing.
Notice the fuel pressure regulator appears to pull it's vacuum off of the same line that the air divertor boxes for the AIR system do on the front. They branch off of a Y.
I can tell you with CERTAINTY that the vacuum connection going to the superram on the back for the air divertor boxes is not a very strong one.
You can't really see it in this picture too well.....
But you can see the flexible line that comes off of the center vacuum fitting RIGHT behind the fuel pressure sending unit. Well I have cut that line to about 8" and it makes 270* of a circle and I have stuck a "donated" portion of formed vacuum line from another area in the end of it. This then sticks into the 90* fitting on the end of the air divertor vacuum connection that used to be plugged into my stock manifold. That last connection is VERY loose. I didn't worry about it before because I thought it was just for the divertors until I thought about it again.
I am REALLY willing to bet I have a major vacuum leak right there, and that it is not pulling the pressure down as far as it shoudl be since it also supplies the vacuum for the AFPR. This may also tell me why I am getting different fuel pressure readings at full throttle. Sometimes it jumps from 37.5 while cruising to 50.5psi and last night I even saw 64.5psi a few times.
I think that a severe leak on this line would result in major fuel pressure increases. Yes or no? I will work on securing that connection immediately.
[Modified by scorp508, 3:11 PM 5/22/2002]
[Modified by scorp508, 3:14 PM 5/22/2002]
05-22-2002, 04:09 PM
#3
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St. Jude Donor '06-'08-'10
Re: (scorp508)
Kinda lonely around here right now.
I'd go ahead and make sure that you are getting the vacumn. Can't hurt.
If you bring down to the Baymont we can all look at it. :D :cheers:
I'd go ahead and make sure that you are getting the vacumn. Can't hurt.
If you bring down to the Baymont we can all look at it. :D :cheers:
05-22-2002, 04:16 PM
#6
Drifting
Re: (scorp508)
Even if that was your problem, that doesn't explain the high readsings above 60.
Say you had no vacuum/weak vacuum on that port. That is just like testing the FP with the vac line disconnected. I am assuming that you want pressure somewhere in the 40-45 psi range at WOT? So you are still way to high.
Say you had no vacuum/weak vacuum on that port. That is just like testing the FP with the vac line disconnected. I am assuming that you want pressure somewhere in the 40-45 psi range at WOT? So you are still way to high.
05-22-2002, 04:17 PM
#7
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Thread Starter
I am assuming that you want pressure somewhere in the 40-45 psi range at WOT? So you are still way to high.
05-22-2002, 04:45 PM
#8
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Re: (scorp508)
Scorp, waltz over to the snap-on truck and get the vacuum brake bleeder with the vacuum gauge on it and pull a vacuum on the AFPR while watching the fuel pressure. You'll then have an idea of how much vacuum it takes to achive a certain pressure. It will also give you an idea if the AFPR is bad.
05-22-2002, 04:58 PM
#9
Le Mans Master
Re: (fiddleplayer)
Without the vacuum line even attached it should be 47psi. That would not explain why you are seeing 50+ with the AFPR adjusted all the way back. I think your problem is elsewhere.
[Modified by Vette92, 2:59 PM 5/22/2002]
[Modified by Vette92, 2:59 PM 5/22/2002]
05-22-2002, 05:45 PM
#10
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Re: I was just thinking about my high fuel pressure and may of figured it out. (scorp508)
I still say put a known good mechanical gauge onto the Schraeder to be sure of the values.
Then set the base value with NO vacuum attached to the AFPR.
If your observed readings ever go above that value, you have a problem with the AFPR or the electronic gauge. Only a positiver pressure in the plenum could make the FP go above that base value.
Then set the base value with NO vacuum attached to the AFPR.
If your observed readings ever go above that value, you have a problem with the AFPR or the electronic gauge. Only a positiver pressure in the plenum could make the FP go above that base value.
05-22-2002, 05:59 PM
#11
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Re: I was just thinking about my high fuel pressure and may of figured it out. (scorp508)
Hey Scorp, where did you get the pic of the vacuum routing? I am planning on replacing all my vacuum lines this summer and that one is laid out really easily. Do you have access to any more?
05-22-2002, 06:05 PM
#12
Race Director
Re: I was just thinking about my high fuel pressure and may of figured it out. (scorp508)
I am with Chris on this one. I think you have some restriction in the return fuel line.
05-22-2002, 06:09 PM
#14
Team Owner
Thread Starter
Have you checked for any blockages or crimps in the return line?
05-22-2002, 06:18 PM
#15
Melting Slicks
Re: (scorp508)
"I was just thinking about my high fuel pressure and may of figured it out"
Scorp gets no love. :)
05-22-2002, 06:20 PM
#16
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Re: (scorp508)
Wish I could help there. Beyond a visual inspection I've got no clue. I just remember that the FMU in my 94 worked via manipulating/blocking the return line to increase fuel pressure.
Jason
Jason
05-22-2002, 06:22 PM
#17
Team Owner
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Re: (Rich B.)
[QUOTE...Scorp didn't receive any "A"'s in English Grammar, either... :D :p: :sleep: [/QUOTE]
English is the only class I've ever failed. :D
English is the only class I've ever failed. :D
05-22-2002, 06:26 PM
#19
Team Owner
Thread Starter
Re: (LPDesRoche)
Just hook it directly to the back of the Super Ram. That how I have always done mine. Never had a problem with high FP.