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Technical Info: 2nd Gen 24 VALVE DRIVETRAIN Technical discussion of second generation (1998 - 2002) 24-valve engine and drivetrain questions, solutions and upgrades.
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Old 1 Week Ago
nd110976 nd110976 is offline
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Default Erratic fuel pressure in 5th gear

I was doing a drive from Vegas to Denver last week. My vp44 took a dump as I was approaching the last exit for Green River. I had to order a rebuild from NAPA because that is the only parts store in Green River. I replaced it in a hotel parking lot and finished the drive. On my way back to Vegas yesterday I noticed that climbing to grade out of Green River that my fuel pressure was all over the place so I down shifted into 4th and it stabilized back to around 9 give or take. Whenever I would shift to 5th it would start bouncing from below zero up to 10 and then stabilize for a few seconds and then start going crazy again. Unfortunately I was in the 120 mile stretch of no services so I rode it out all the way to Richfield with erratic pressure. I swapped my filter in Richfield and same issue. So I just hoped and prayed and pushed all the way to Vegas. There were no real noticeable performance issues except on the big grade out of Green River when I noticed it and got stuck downshifting to try to keep my pressure up. Could this be a bad sending unit for my gauge? It is strange to me that it is only occurring in 5th gear at around 2300 RPM. Idle and 1-4 are all stable at 7 WOT and 11ish idle. In town with up and down speeds it is stable in 5th. I'm going to replace my Airdog life pump today just in case since it is a few years old. If that solves the problem should I pull the new VP44 and go warranty it at NAPA since it did a few hundred miles with the crazy fuel pressure? I'm kind of thinking that may be why my other VP44 went out. Maybe the pressure was doing that before and I just didnt notice. It went out with no warning. Usually i get some signs like a dead pedal or performance issues. This time it was cruise kicked off, engine light came on, and engine died.
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Old 1 Week Ago
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CaptainCummins CaptainCummins is offline
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If you have an electric gauge, the only real tried and true way to check is to install a manual gauge. It doesn't have to a be a permanently installed gauge, just by a fuel pressure test kit and tie the gauge somewhere where you can see it. A suction side leak on the airdog can cause erratic pressure too.
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Old 1 Week Ago
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The lift pump fuel pressure needs to be known,
Fuel pressure test kits are available at most chain type auto parts stores. The gasser kits work fine.




Screw the connector on the fitting of the injector pump on the driver's side of the engine.
Turn the keyswitch just enough to "bump" the starter to get The Free 25 Second Lift Pump Run.





Stock spec is 10psi+, most folks look for 15psi.
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01.5,Red QC Sport SWB,HO,6spd,4x4,cowl hood, Drag Comp,4"ex., fuel press. gauge, boost&pyro gauges, bhaf, single Holley lift pump next to the fuel tank/13psi WOT, Vulcan Big Line, cheapo fuel cooler, Amsoil in the trans. & Valvoline in the pan, 63-65-.70A/R, ARP studs, kevlar/ceramic SD clutch, jammer 100's

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Doc says I'm in pretty good shape for an 83 year old guy.....one of these days I need to tell him I'm 59.


Time to turn so's you don't burn.
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Is the Check Engine light On?
Turn the keyswitch On-Off-On-Off-On then look at your odometer for Trouble Codes and report back.
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01.5,Red QC Sport SWB,HO,6spd,4x4,cowl hood, Drag Comp,4"ex., fuel press. gauge, boost&pyro gauges, bhaf, single Holley lift pump next to the fuel tank/13psi WOT, Vulcan Big Line, cheapo fuel cooler, Amsoil in the trans. & Valvoline in the pan, 63-65-.70A/R, ARP studs, kevlar/ceramic SD clutch, jammer 100's

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Originally Posted by jetfueljockey View Post
Doc says I'm in pretty good shape for an 83 year old guy.....one of these days I need to tell him I'm 59.


Time to turn so's you don't burn.
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Old 6 Days Ago
nd110976 nd110976 is offline
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The engine light isn't on and it shows no codes. My lift pump is at 13 PSI. I was wrong about the AirDog. It is a Raptor, I'm not sure what made me think it was an AirDog. It is really strange to me that it is only happening in 5th gear with no load on the truck. It doesn;t do it in town while driving due to speed changes, it is only on the open road at 75-85 while cruising. I can't get it to do the same thing in any other gear or any other situation.
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Old 6 Days Ago
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13 psi isn't bad, that's my cruising pressure.
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01.5,Red QC Sport SWB,HO,6spd,4x4,cowl hood, Drag Comp,4"ex., fuel press. gauge, boost&pyro gauges, bhaf, single Holley lift pump next to the fuel tank/13psi WOT, Vulcan Big Line, cheapo fuel cooler, Amsoil in the trans. & Valvoline in the pan, 63-65-.70A/R, ARP studs, kevlar/ceramic SD clutch, jammer 100's

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Originally Posted by jetfueljockey View Post
Doc says I'm in pretty good shape for an 83 year old guy.....one of these days I need to tell him I'm 59.


Time to turn so's you don't burn.
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Old 5 Days Ago
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smokediver smokediver is offline
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Bo...I I say Boy...You Driving Too Fast!!
Could it be that your demand for fuel only exceeds your supply in 5th gear at higher speeds? Lower gear just doesn't quite get it past the breaking point?
Might want to drop the tank and check the screen. I've had two that acted all crazy and the screen was full of gunk, only problem.
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'09, quad cab, Laramie, 2WD, Dually, 6.7, auto.
H&S mini maxx, something fell off under the truck 270k mi
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Last edited by smokediver; 5 Days Ago at 02:37 PM..
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Old 4 Days Ago
nd110976 nd110976 is offline
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It's Utah and the limit is 80 mph, so "when in Rome". Up until now I have never had this issue. I have seen pretty much everything this truck has thrown at me. I'm closing in on 460k miles and I drove it off the lot in January 2001. I am getting better mileage now than it ever has in the past and it seems to just keep kicking. I took it out and drove it yesterday and couldn't get it to do it again. I'm wondering if I got bad fuel or somehow got air in the system. I have to do a drive to Iowa in the next couple weeks so I think I'll change the lift pump just as a precaution.
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2001 4x4 2500 QC, 3.54 gears, superchips max-tuner, 4" exaust, BHAF, Boost Fooler, Westach FP gauge, BFG 285/75-16
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  #9  
Old 4 Days Ago
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If you mount your lift pump on the frame rail, in front of the fuel tank, it'll be gravity fed and won't pull air into the suction side of the pump.
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01.5,Red QC Sport SWB,HO,6spd,4x4,cowl hood, Drag Comp,4"ex., fuel press. gauge, boost&pyro gauges, bhaf, single Holley lift pump next to the fuel tank/13psi WOT, Vulcan Big Line, cheapo fuel cooler, Amsoil in the trans. & Valvoline in the pan, 63-65-.70A/R, ARP studs, kevlar/ceramic SD clutch, jammer 100's

Quote:
Originally Posted by jetfueljockey View Post
Doc says I'm in pretty good shape for an 83 year old guy.....one of these days I need to tell him I'm 59.


Time to turn so's you don't burn.

Last edited by Clunk; 4 Days Ago at 07:17 PM..
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  #10  
Old 2 Days Ago
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smokediver smokediver is offline
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Copy the 80.
I would suspect you have the big line kit and the no clamp fittings maybe??
I found out once upon a time that screw type clamps can pinch the hose up and let it suck air right under the screw.
Believe it or not, the spring type clamps you squeeze with a pair of pliers actually seal better.
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'07, megacab, 2WD, Dually, 6.7, auto,
H&S XRT, jasper turbo, ETE tranny, 490k mi !!
'09, quad cab, Laramie, 2WD, Dually, 6.7, auto.
H&S mini maxx, something fell off under the truck 270k mi
My Other Truck is a Fire Engine!!
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