My fuel pressure gauge is all over the map - sometimes

[Kyle]

I recently installed a fuel pressure gauge. Most of the time it sits a 13psi at idle and never goes below 7 at full throttle.

Once in a while the needle dances all over the place between 0 and 6. It seems to do this more often when I start up cold. But sometimes it goes into this "mode" while warm and driving. After a little while it jumps back up to 12 or so and the needle settles down.

What's up? Do I have a bad lift pump or is there foam/air in the top of the filter by the sender?

 

[BIG BOB]

Kyle,

In cold tempertures (below freezing), when I first start my truck the fuel pressure fluctuates from 0 to 6 pounds. I just let it idle for about 3 to 4 minutes and then it goes up to 12 pounds at idle and not less that about 5 or 6 pounds at WOT, and never have a problem after engine warms up, just when cold start ups. I don't know if the paraffin in the diesel is causing this or not.

 

[ROAD WARRIOR]

Mine would do the exact same thing. I asked my dealer about it and they said it was fine if there weren't any driveability problems. It made me unconfortable watching it dance after it was warm, so I replaced it with a new pump from JRE. Since this time, it stabalizes much faster at start up and hasn't screwed up after being up to temp.

I recall Chad Sheets having this exact problem also before his totally died.

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'99 2500 4x4 QC, 5SP, 4. 10, LSD, SLT, DR. PERFORMANCE PHASE III, BANKS 4" EXHAUST(no muffler), BANKS BOOST& EGT GAUGES, SW FUEL PRESSURE GAUGE, BILLET ALUMINUM TURBO INTAKE HORN, AMSOIL AIR FILTER, ROCKFORD FOSGATE AUDIO SYSTEM, DMI QUICK & EASY HITCH, BD 2 LOW KIT, NRA MEMBER

 

[illflem]

Sounds like you two have 24v because of the low pressures,but with a mechanical pump like the 12 valves the pulsations from the lift pump will put the gauge needle all over the place and eventually ruin the sender if you don't use a gauge snubber or restrictor. I'm not sure if the electrical pump also does this.

 

[Ted Jannetty]

Kyle, sounds like your lift pump is on the way out, The Pressure should not drop below 9 psi with a stock pump and a clean filter.
The pressure fluctuation can be a result of a bad armature in the electric pump.

We are also working on a electric fuel pump system for the 12 valve, testing is underway as we speak.



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Ted Jannetty, Owner President, Jannetty Racing Enterprises, Inc.
97 3500 4x4 club cab 5spd. RED, JRE custom power kit, JRE 4" exhaust
JRE 1/2 inch fuel system, Bosch 300 hp injectors, Prime loc,
Cummins chrome kit, US Gear 20% over drive, 3. 54 posi, Autometer
Ultralite 50lb. boost, and Pyrometer, BD exhaust brake.
Horton fan clutch

99 Ski-Doo 800 Formula III Pipes, reeds, studs and clutching 172 hp
99 Honda Forman 450 ES jet kit, pipe, lift kit, 27" Mud Runners
2001 Ski-Doo MXZ 800 X stock for now 140 hp
2000 TransAm Ram Air WS6 Flowmaster, K&N, Granatelli Mass air meter, LS1 Lid 370 hp
1973 Camaro Rally Sport Street Strip 850+ HP

 

[RobG]

Ted:

Does your 9 psi statement also apply to an ETH? I've seen my pressure drop to 5 psi at WOT, with an idle of 13-15 psi.

Rob


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2001. 5 RAM 3500 QC 4x4 ETH/DEE Silver/Agate 4. 10 USGear OD, Rickson 19. 5 Wheels, Edge EZ, SPA Guages, Psychotty, Firestone Airbags, Hellwig Rear Swaybar, Torklift Superhitch & Camper Tiedowns, Mag-Hytec Diff Cover, and more!

 

[JohnB]

My 2001 jumps right to 14. 5 psi when started and stays rock steady. Stays above 12 under load.

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01 2500,SB, Club Cab, 5spd,3. 54 LS, Bright White, Camel Leather. 01 Sunnybrook 27' 5ver--All Stock

 

[Brandon]

move post filter press away from pump... ...

B... ... ... ... ... .....

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END THE OPPRESSION FREE HVAC NOW
Danelle's Dodge

 

[Kyle]

Just to clarify. "Cold" startup for me here in Phoenix is about 50 degrees. My manifold heater only comes on a few mornings a year.

Based on the absence of any comment on the subject, I'm assuming no one thinks this could be caused by air bubbles in the fittings that the sender screws into. Is this a safe assumption?

By the way, both my senders (before & after the filter) show the same thing at the same time. They both dance when they're dancing, they both show steady when it's working. That rules out the senders. It might also rule out the bubbles since they're each in two different fittings??????

Oops, Yes, it's a 24-valve (1999) model.

My sig is below:

Ted, do you have something to replace my electric lift pump? Maybe something worthy of a 1/2" fuel line?

1999, NV4500HD, QC, 4x4, 3. 54, 8' Bed, Rhino Lining, 315/75R16s on 16x8 Eagles, 2" Skyjacker front lift, Edelbrocks, Glasstite, Racor LFS, 3 AutoMeters on the A-Piller, MagHytec


[This message has been edited by Kyle (edited 03-02-2001). ]

[This message has been edited by Kyle (edited 03-02-2001). ]

 

[Neal Cassady]

Kyle,

Entrained air in diesel fuel has been a subject of debate for years. Do a web search on the Fuel Preparator, you will be reading for days. I know quite a few OTR drivers that run them on their own rigs. I think Enterprise Engine sells/adapts them to Cummins on the Ram platform. I have been thinking about adding one to my truck.

Dave D

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2001. 5 QC, LB, 4x4, Auto, 3. 54, Everything but Leather, Bright Silver Metallic, ARE K Series, Diprocal EGT, Boost and transmission Temp in an Autometer Dash Pod, Westin CPS Platinum Step Bars - Black on Stainless