low fuel pressure, im at a loss, need suggestions. - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

Reply
 
 
 
Thread Tools Search this Thread
Old 05-10-2008, 05:49 PM   #1
Senior Member
Certified GM nut
Thread Starter
 
Join Date: Oct 2006
Location: burb of detroit. 2 miles north of 8 mile Rd.
Posts: 2,028
Thanks: 0
Thanked 0 Times in 0 Posts
samueljackson is on a distinguished road
Default low fuel pressure, im at a loss, need suggestions.

before doing this, http://www.bonnevilleclub.com/forum/...ic.php?t=98241, i want to be sure that my pump is causing the low pressure. it idles around 38 psi. and will drop to 30 at WOT.

so far i have gone over every vacuum line. I have a consistant 23-25 in/Hg on my gauge.

i had a small leak on the egr tube where it bolts to the egr plate. i used the same egr gasket that i did on the sc side and both now seal.

when i take the vacuum line off the fpr, the fp gauge pegs right to 46-48 psi. and it will stay there if i rev it. and the second i touch the vac line back to the fpr, the fp goes right back to 38 psi. and if i rev it still drops.

i have also tried a different fpr. I had the same results with both.

i also had flow matched injectors, which i swapped back to the old injectors and had no change.

so where do i go from here?
samueljackson is offline   Reply With Quote
Old 05-10-2008, 07:35 PM   #2
Senior Member
Certified GM nut
 
Join Date: Oct 2005
Location: Western New York
Posts: 1,942
Thanks: 0
Thanked 0 Times in 0 Posts
Technical Ted is on a distinguished road
Default

If I'm following what you did then it sounds like you're getting too much vacuum to the FPR.
Technical Ted is offline   Reply With Quote
Old 05-10-2008, 08:17 PM   #3
PopaDopaDo
True Car Nut
 
popatim's Avatar
 
Join Date: Jan 2005
Location: NY
Posts: 4,957
Thanks: 0
Thanked 0 Times in 0 Posts
popatim is on a distinguished road
Default

Which car is this for?

Where are you measuring the vaccum at? Can you tee off the FPR line and see what you're getting there?

I thought fuel pump too but you should see the same fuel pressure drop with the 'no vacuum FPR' at wot but you say its steady @48ish ... very odd.
popatim is offline   Reply With Quote
Old 05-11-2008, 01:07 PM   #4
Senior Member
Certified GM nut
Thread Starter
 
Join Date: Oct 2006
Location: burb of detroit. 2 miles north of 8 mile Rd.
Posts: 2,028
Thanks: 0
Thanked 0 Times in 0 Posts
samueljackson is on a distinguished road
Default

Quote:
Originally Posted by Technical Ted
If I'm following what you did then it sounds like you're getting too much vacuum to the FPR.
yes, thats correct. what makes me get too much vacuum?

Quote:
Originally Posted by popatim
Which car is this for?

Where are you measuring the vaccum at? Can you tee off the FPR line and see what you're getting there?

I thought fuel pump too but you should see the same fuel pressure drop with the 'no vacuum FPR' at wot but you say its steady @48ish ... very odd.
this is in my Buick.

i tested vac inline with the fpr, and also directly on the tree where the fpr would be, when i disconnected it. both had the same readings.

when i said it didnt drop after i pulled vac off the fpr, that was just revs. not wot. i was in park giving it the same revs that i did when i saw the drop, as if the fpr was hooked up.
samueljackson is offline   Reply With Quote
Old 05-11-2008, 02:10 PM   #5
Senior Member
Certified GM nut
 
Join Date: Oct 2005
Location: Western New York
Posts: 1,942
Thanks: 0
Thanked 0 Times in 0 Posts
Technical Ted is on a distinguished road
Default

I just connected a vacuum gauge to my son'* car & we have 13 -14 in/Hg at idle. The pressure stays fairly constant when rev'd up slowly. With quick blips of the throttle the vacuum drops to 0.

I've been trying to think what could cause too much vacuum & I'm not coming up with much. I was wondering if a clogged air filter was a possibility but can't believe the car would be driveable if the filter was so plugged up that it was causing problems at idle. I'm sure you'll know if the filter'* been neglected or not.

See if your vacuum drops with quick blips of the throttle.

Come on guys - what would cause excessive vacuum? Is the IAC a possibility?
Technical Ted is offline   Reply With Quote
Old 05-11-2008, 02:47 PM   #6
Senior Member
Certified GM nut
Thread Starter
 
Join Date: Oct 2006
Location: burb of detroit. 2 miles north of 8 mile Rd.
Posts: 2,028
Thanks: 0
Thanked 0 Times in 0 Posts
samueljackson is on a distinguished road
Default

well, its definitely not a clogged air filter. but, what if the fwi is too much for me? is that possible?

should i put the 2.8 in pulley on?
samueljackson is offline   Reply With Quote
Old 05-11-2008, 03:29 PM   #7
Senior Member
True Car Nut
 
Join Date: Mar 2004
Location: Ames, Iowa
Posts: 3,066
Thanks: 0
Thanked 1 Time in 1 Post
bill buttermore is on a distinguished road
Default

Too much vacuum would have to be a restriction in the supply of incoming air. Let'* see, isn't there something called ported vacuum? Those ports (I think) are upstream of the throttle plate. Are we sure the FPR vacuum line is connected at the correct spot? Any port into the intake manifold should provide the maximum vacuum the engine can produce. I'll go look to see where my FPR draws its vacuum....goes to see.....on my NA Series II, the FPR tap is on the engine side of the throttle plate.

How about a plugged up or stuck closed PCV valve? That would seal up a source of air that is normally available to the intake through the crankcase and maybe would increase the vacuum reading.

It would seem if the IAC were stuck closed, there would be problems with idle speed.
bill buttermore is offline   Reply With Quote
Old 05-11-2008, 04:08 PM   #8
Senior Member
Certified GM nut
Thread Starter
 
Join Date: Oct 2006
Location: burb of detroit. 2 miles north of 8 mile Rd.
Posts: 2,028
Thanks: 0
Thanked 0 Times in 0 Posts
samueljackson is on a distinguished road
Default

i can try the iac that was on the gen 2 tb.
the pcv is new.
samueljackson is offline   Reply With Quote
Old 05-11-2008, 04:28 PM   #9
Senior Member
Certified GM nut
 
Join Date: Oct 2005
Location: Western New York
Posts: 1,942
Thanks: 0
Thanked 0 Times in 0 Posts
Technical Ted is on a distinguished road
Default

Give us some more info.
You went to a Gen 3 supercharger
Flow matched injectors
& Fender well intake. Yeah - I see the air filter isn't clogged.

I don't think any of the above things are going to increase vacuum.
What happens to the vacuum when you blip the throttle?

What throttle body are you running?
What made you look into the fuel pressure - P0171? I guess that'd be code 34 on a 92.
Where does the FPR vacuum line come from on your engine?
How does it idle?
Anything else you think we should know?
Technical Ted is offline   Reply With Quote
Old 05-11-2008, 04:47 PM   #10
Senior Member
Certified GM nut
Thread Starter
 
Join Date: Oct 2006
Location: burb of detroit. 2 miles north of 8 mile Rd.
Posts: 2,028
Thanks: 0
Thanked 0 Times in 0 Posts
samueljackson is on a distinguished road
Default

Quote:
Originally Posted by Technical Ted
Give us some more info.
You went to a Gen 3 supercharger
Flow matched injectors
& Fender well intake. Yeah - I see the air filter isn't clogged.
yeah, im sorry, i should have linked this http://www.bonnevilleclub.com/forum/...687&highlight= that would have helped

Quote:
Originally Posted by Technical Ted
I don't think any of the above things are going to increase vacuum.
What happens to the vacuum when you blip the throttle
it will goe toward atmospheric. or 0 on the gauge. it only moves about 5in/hg. but it pings back to about 30 for a second. and usually settles just above 25 in/hg.


Quote:
Originally Posted by Technical Ted
What throttle body are you running?
What made you look into the fuel pressure - P0171? I guess that'd be code 34 on a 92.
Where does the FPR vacuum line come from on your engine?
How does it idle?
Anything else you think we should know?
i have a 94-95 L67 tb, that matches the gen 3 m62.

what made me look into the fuel pressure is bc of the chip being re-flashed. i needed to make sure all parameters were in spec. at first it was extremely lean and ran horrible. but no KR. then i put in a tb screen and it helped drastically in the feel of the pedal. but not too much on the scanner. it was better, but not where it should be. so from there i started testing fuel pressure. finding it was low, i started to conclude that the NEW pump was not keeping up. but i wanted to be sure it wasn't the regulator. so going over the vac line MANY times, i decided to pull the vac at the fpr, and i saw the 45 psi on the fp gauge. so would that indicate the fpr and pump to be good?


**edit** the fpr is on the middle port of this vac tree.
samueljackson is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Low oil light/low oil pressure 3800 Impala 2k2cse Chevrolet 14 05-16-2013 05:38 AM
possible causes of low fuel pressure. biggreenpontiac 1992-1999 3 01-02-2009 04:35 PM
recent P0300 and now low fuel pressure LittleHoov Bonneville GXP/ Northstar Powered Cars 6 02-15-2007 07:29 AM
Fuel Leak from High pressure fuel line...need guidance Rich97bonny 1992-1999 5 10-18-2005 02:26 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 12:01 AM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.