Fuel Pressure while Driving - Diesel Place : Chevrolet and GMC Diesel Truck Forums
 
Home Forum Market Place Garage Lounge (0) Tuning Library DTC Tool Register Vendors
Go Back   Diesel Place : Chevrolet and GMC Diesel Truck Forums > GM Diesel Engines > 6.5L Diesel Engine
Register FAQ Forum Rules My Replies My Threads Mark Forums Read Auto EscrowAuto LoansInsurance

DieselPlace.com is the premier Duramax Diesel Forum on the internet. Registered Users do not see the above ads.
Reply
 
LinkBack Thread Tools
Old 11-28-2012, 12:28 PM   #1 (permalink)
SickSpeedMonte
Diesel Technician
 
SickSpeedMonte's Avatar
 
Join Date: Oct 2010
Posts: 186
iTrader Score: 0 reviews

Fuel Pressure while Driving

Did a couple searches, found nothing.

Those of you with fuel pressure gauges that you can monitor while driving, what pressure do you see under what driving conditions? Also, what LP do you have?

I have a stock replacement Airtex LP (I know... I found out that I should have gone Delco afterwards) and if I go more than about 75% throttle at higher RPM, I can get the fuel supply pressure gauge to drop to zero. The truck is stock engine wise.

I'm wondering if I might have screwed up my check valve/pressure regulator on the front of the IP by blowing air at it at one point when I took it off. Although, I get 7psi at cold idle, about 6 or so at warm idle, so it definately seems like a flow rate problem. The harder I push the engine (the greater the fuel demand it seems), the lower the supply pressure drops.
__________________
==================================================
1993 Chevy K3500 CCLB Dually, 6.5TD, 4L80e, 4WD on Alcoa's with 265/70R19.5's.
Raptor 100 GPH LP, OPS realy mod, Lube Specialists oil cooler kit, Glow Shift boost and supply fuel pressure gauges, 3" stainless DP, 4" stainless turbo back, 2.25" stainless crossover, all new hardlines underneith, and a 14 bolt full floater out of a Krispy Kreme delivery van
Offline  
Reply With Quote
Sponsored Links
Advertisement
 
Old 11-28-2012, 12:34 PM   #2 (permalink)
racer55
6.5TD Post Addict
 
racer55's Avatar
 
Join Date: Jul 2010
Location: Scugog Island Ontario Canada
Posts: 9,449
iTrader Score: 0 reviews

Ontario Diesel Place Chapter Member

Old School Oil Burners (Old SOBs) Member

Seeing 0psi under hard acceleration with a stock style LP is not uncommon,what you don't want to see is the IP draw vacuum under those conditions-or ever for that matter.

Vacuum would indicate a fuel restriction.

BTW;where is the pressure gauge connected in the fuel system?
Pre/post filter?
__________________
No longer a 6.5 owner
2005 Chev K3500 CCLB Dmax

Diagnostic Checklist 2.0
OBD1 Codes
OBD2 Codes
6.5 FAQ
Carcode & TDCO Instructions
Offline   Reply With Quote
Old 11-28-2012, 01:33 PM   #3 (permalink)
FloridaHorseman
Diesel Master
 
FloridaHorseman's Avatar
 
Join Date: May 2011
Location: Lakeland, FL
Posts: 3,203
iTrader Score: 0 reviews

Quote:
Originally Posted by SickSpeedMonte View Post
Did a couple searches, found nothing.

Those of you with fuel pressure gauges that you can monitor while driving, what pressure do you see under what driving conditions? Also, what LP do you have?

I have a stock replacement Airtex LP (I know... I found out that I should have gone Delco afterwards) and if I go more than about 75% throttle at higher RPM, I can get the fuel supply pressure gauge to drop to zero. The truck is stock engine wise.

I'm wondering if I might have screwed up my check valve/pressure regulator on the front of the IP by blowing air at it at one point when I took it off. Although, I get 7psi at cold idle, about 6 or so at warm idle, so it definately seems like a flow rate problem. The harder I push the engine (the greater the fuel demand it seems), the lower the supply pressure drops.
Even though it's an Artex, first make sure you got the correct Lift Pump for a '93. Airtex should be #3158 w/9.5-13 PSI output. Airtex #3309 w/6-8 PSI output is for '94 & up (severely under-performing pump). So make sure you have the right LP.

You also have the mechanical DB2 injection pump vs. the DS4 electronic model '94 & up. For some unfathomable reason GM decided the electronic IP didn't need the same supply fuel pressure the mechanical pump did.

With either LP, the 3309 or 3158, your cold/warm idle numbers would look about right, although I would prefer to see closer to 10 PSI at warm idle on a DB2. Under WOT you should see no less than 2 PSI on the DB2. That leads me to believe you may have the wrong LP for a '93 or it's time to change the fuel filter cartridge. These suggested pressures are measured at the IP inlet.

You may also want to put a short piece of clear hose on the IP fuel return line outlet and watch for air bubbles. If you have the correct LP for a '93 you could also be losing 2 PSI of fuel pressure if the O-rings on the LP inlet/outlet side are compromised/missing or the O-ring on the FFM canister isn't seated properly. But air getting in should also create a symptom of hard starts or momentary lag in throttle response. A restricted or clogged fuel sock on the tank sending unit could also be responsible for reducing overall line pressure if everything else checks out OK. ~FH
__________________

1994 Chevy K1500 Z71, 6.5L TD 145,000 miles, bumper mount PMD, LP relay mod, filter sock delete -SOLD-
1998 Chevy K3500, 454 horse hauler , 175,000 miles, tuned flow-through exhaust, pillar gauges (vac, trans temp, volts), electric cooling fans, external trans cooler & fan, manual TCC lockup mod, limo tint, front & rear brush guards, B&W G/N flip hitch, spray-in bed liner, chrome wheel inserts


Engine "No Start" Checklist
Diagnostic Checklist
OBD1 Trouble Codes
OBD2 Trouble Codes

Last edited by FloridaHorseman; 11-28-2012 at 01:39 PM.
Offline   Reply With Quote
Old 11-28-2012, 02:08 PM   #4 (permalink)
JMJNet
Diesel Laureate
 
JMJNet's Avatar
 
Join Date: Feb 2006
Location: Richardson, TX
Posts: 12,143
iTrader Score: 0 reviews

The Suburban Club Member

The answer is hidden in a lot of thread.

Usually around 6-8 psi idle and 2-4 psi at WOT (ideal).
Although sometimes it goes to 0 psi intermittently as long as not vacuum racer55 said.

Of course, everything is depend on where the gauge is located.
__________________
1995 GMC Suburban:
PMD in Bumper
4" Warpspeed Exhaust
KD LP/OPS Harness
Bosch Duraterm GP
Heath Turbo-Master
Chevron's XLP Diesel Additive
Online   Reply With Quote
Old 11-28-2012, 02:42 PM   #5 (permalink)
Jake
Diesel Master
 
Jake's Avatar
 
Join Date: Oct 2003
Location: Hayes, VA
Posts: 1,523
iTrader Score: 0 reviews

Old School Oil Burners (Old SOBs) Member

DelMarVa Diesel Club Member

I see 5-6 psi at idle. 3-4 psi at cruise. I have a stock 93 lp.
__________________
Jake Brodersen

96 K2500 Suburban Peninsular Diesel 6.5TD
3.73 gears, Heath Remote PMD, Heath Heavy Duty Lift Pump, Banks 3" downpipe, BD 4" exhaust, JK headlight booster kit,
Heath HP4 PCM, manual glow plug switch, vacuum pump eliminated
Gauges: fuel pressure, manifold pressure, and EGT in a 3 gauge pod, plus engine oil and trans. oil temp on top of the dash. Bilstein shocks and Hotchkis sway bars on the greasy side. High idle mod too. Grover 1510 (Firetruck) air horn. Four wheel disc brakes.

2012 Acura TL V-6 (280hp)
2006 Harley Springer Softail FXSTSI (already modded and putting out more power)
2002 Chevy S-10, step side, regular cab, 2.2 litre w/5 speed
1992 Chevy S-10, extended cab, 2.8 V-6 w/5 speed
Offline   Reply With Quote
Old 11-28-2012, 05:16 PM   #6 (permalink)
Deezel
Diesel Technician
 
Join Date: Jul 2008
Posts: 478
iTrader Score: 0 reviews

Low pressure more offten than not is a stopped up sock in the tank.
__________________
98 3500 dually
Offline   Reply With Quote
Old 11-28-2012, 09:32 PM   #7 (permalink)
Graplr
Diesel Specialist
 
Graplr's Avatar
 
Join Date: Aug 2009
Location: Stillwater, Minnesota
Posts: 762
iTrader Score: 0 reviews

Minnesota/Western Wisconsin DP Club Member

I see similar to what Jake stated. 5-6 at idle. Normal highway/freeway speeds around 3-4. If I hit it hard it to around or below one. Usually to drop to 0 or vacuum (which I try to never do) I would have to be getting into it very hard going up a decent incline.

Mine is located inbetween the filter and IP.

I'm not sure which pump I have. I know it was AC Delco but I am unsure if it is the 93 or 94 up pump. I replaced it 1.5 years ago. I assume it is the 94 up. I think I have the box still, I'll check it out.
__________________
Ryan
1994 Chev Suburban K2500 6.5 244k miles
-Diamond Eye Exhaust with muffler & 2.5" FloPro Crossover Pipe
-LubSpec Oil Cooler Kit
-Webasto Diesel Coolant Heater w/Remote Start
-Remote PMD on Heat Sync in bumper, HID Headlights w/new lenses
-Newer IP, New Bosch Injectors, New Bosch Duraterm Glow Plugs, Newer Radiator
-PYO Aluminum Wheels, Bridgestone Dueller II A/T tires
-Boost, Fuel Pressure, EGT Gauges, K47 intake w/Amsoil EaA 112 Air Filter
-Rebuilt Transmission @ 227k miles
-LP Relay Mod, High Idle Switch Mod, Glow Plug Override Mod, Battery Terminal Mod
-New OPS, Batteries, Brakes, Starter, Alternator, Fuel Lines, Lift Pump, Vacuum Pump
-GMTD Scan Tech
-599 Block from the factory
Offline   Reply With Quote
Old 11-29-2012, 04:33 AM   #8 (permalink)
oil pan 4
Diesel Master
 
Join Date: Apr 2006
Location: clovis, NM
Posts: 2,557
iTrader Score: 2 reviews

With my low pressure carquest fuel pump I see 4psi at idle, 2psi normal driving. It likes to drop to 0 when going up hills.
With my holley blue fuel pump I get about 13 psi at idle and no less than 6psi flooring it.
I plumbed my fuel pressure gauge right before the injector pump.
__________________
1984 Suburban C10 with C20 rear spings, Compound Turbocharged with HE351VE and T76, Intercooled, TH700, 3.42 gears ?posi?
P&P GM#162 heads, 506 block, DB2829 injector pump, J-code intake manifold, Pennsular diesel upper plenum.
Banksturbo and HMMWV manifolds, custom cross over, 3'' stainless down pipe and 4'' straight pipe exhaust.
Aluminum 2 core radiator, Electric radiator fans (16''+16''), Meziere electric water pump (55gpm), HD '92+ 6.5L water crossover, grill shutters, Air2oil cooler, 16 core trans cooler, 2 block heaters, two G183 intake heaters, 60G plugs, 3500w coolant heater. ISSPRO tach.
31'' yoko AT-S tires.
Offline   Reply With Quote
Old 11-29-2012, 09:14 AM   #9 (permalink)
Jake
Diesel Master
 
Jake's Avatar
 
Join Date: Oct 2003
Location: Hayes, VA
Posts: 1,523
iTrader Score: 0 reviews

Old School Oil Burners (Old SOBs) Member

DelMarVa Diesel Club Member

Maybe I should look into the Airtex pump. The specs look good. I can run fuel pressure to zero just by dropping my foot. Jake
__________________
Jake Brodersen

96 K2500 Suburban Peninsular Diesel 6.5TD
3.73 gears, Heath Remote PMD, Heath Heavy Duty Lift Pump, Banks 3" downpipe, BD 4" exhaust, JK headlight booster kit,
Heath HP4 PCM, manual glow plug switch, vacuum pump eliminated
Gauges: fuel pressure, manifold pressure, and EGT in a 3 gauge pod, plus engine oil and trans. oil temp on top of the dash. Bilstein shocks and Hotchkis sway bars on the greasy side. High idle mod too. Grover 1510 (Firetruck) air horn. Four wheel disc brakes.

2012 Acura TL V-6 (280hp)
2006 Harley Springer Softail FXSTSI (already modded and putting out more power)
2002 Chevy S-10, step side, regular cab, 2.2 litre w/5 speed
1992 Chevy S-10, extended cab, 2.8 V-6 w/5 speed
Offline   Reply With Quote
Old 12-03-2012, 12:21 PM   #10 (permalink)
SickSpeedMonte
Diesel Technician
 
SickSpeedMonte's Avatar
 
Join Date: Oct 2010
Posts: 186
iTrader Score: 0 reviews

Thanks for the info on the two different Airtex pumps, I didn't know that.

I told the guy it was a '93, but I guess that doesnt mean much. I'll check the PN. It's still under the warranty, so if they gave me the wrong one I don't see it being a problem to swap out.

The pressure sender for the gauge is mounted just before the filter. I know, it should be after the filter. I'll probably change it around soon.

Believe me, I've been through the whole sock thing... the hard way. I ended up with a gasoline sock on my replacement pickup-tube assembly and later found out that there was an AC-Delco diesel sock, which now lives in my tank. The filter, lines, fuel manager, o-rings, pickup, sock, and LP are all new (<5,000 miles).
__________________
==================================================
1993 Chevy K3500 CCLB Dually, 6.5TD, 4L80e, 4WD on Alcoa's with 265/70R19.5's.
Raptor 100 GPH LP, OPS realy mod, Lube Specialists oil cooler kit, Glow Shift boost and supply fuel pressure gauges, 3" stainless DP, 4" stainless turbo back, 2.25" stainless crossover, all new hardlines underneith, and a 14 bolt full floater out of a Krispy Kreme delivery van
Offline   Reply With Quote
Sponsored Links
Advertisement
 
Sponsored Links
Advertisement
 
Reply

Thread Tools

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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Fuel rail pressure sensor or fuel pressure reg?? Please help blackmax001 Duramax Third Generation: 2006-2007.5 (LBZ & LLY) 3 06-01-2012 08:12 AM
Fuel Pressure, Rail Pressure and 100 psi boost gauge Rhall Closed / Archived Marketplace Ads 5 03-07-2011 02:44 AM
What is the difference between oil pressure and fuel pressure gauges? whatnot Interior 3 07-27-2009 01:59 AM
nos remoter opener, Nos pressure gauge, and fuel pressure guage chaseum Closed / Archived Marketplace Ads 0 10-10-2006 07:23 PM


All times are GMT -4. The time now is 07:38 PM.


Shoutbox provided by vBShout v6.2.1 (Lite) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd. Runs best on HiVelocity Hosting.
© AutoGuide

SEO by vBSEO 3.6.0