Questions about fuel pressure readings

[ROAD WARRIOR]

After reading this forum about lift pump failures, I decided I would install a SW fuel pressure gauge(electronic sender).
When I start the engine after setting over night, the pressure reads 11psi with key on and once the engine starts, the pressure fluctuates between 0 and 8psi for up to ten minutes idling or driving. Once the pressure stablizes, it reads 12 - 13psi and drops to 10psi at WOT. Sometimes when in fifth gear and I give the throttle a quick push and back off, the fuel pressure will start dancing around between 0 and 8 psi for up to a minute and it will then level back off at 12 - 13psi. If I shut the motor off and restart it right away, the fuel pressure will immediately level off at 12 - 13 psi. It seems to look good except for those two scenarios. Also one time before I had my fuel pressure gauge, I drained my fuel/water seperator, the motor almost died a couple of times after I started it as I was leaving the gas station. It has never done this before.
Could all of these symptoms be caused by the lift pump losing its prime?
Any information you guys could give me would be greatly appreciated.

Dan

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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

 

[Chad Sheets]

Is it cold where you live? In the summer, my fuel psi is good to go. Once it gets cold I get what you do for about 5-10 min. I buy a quart of Howels (sp) fuel treatment at the truckstop and put 1/4 of it in every full tank. It stops the fluctuation. Improves lubricity, raises the cetane number and seems to fix my fuel psi problem.

You never ever ever want 0 psi on that fuel gage. The injection pump is cooled and lubricated by diesel fuel. Also where did you put the gage? Before the filter, after the filter?

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Always ready to help!
2000 2500 Red Sport quad cab, 4x4, K&N, DDI's, straight piped, boost, pyro and fuel pressure gages, Hot Power Edge, mean looking set of 33. 5" tires, Snap On diamond tool box, Marine Corps window sticker, Semper Fi!

1972 340 Cuda'. Original tripple Black, 340 car w/air. Good clean car, super stock springs, Weld Prostars, shaker hood, strong 340 with a 727/4000 stahl, 4. 56... . Bombs away!
NRA Life Member. http://www.geocities.com/chadsheets

 

[ROAD WARRIOR]

I live in Northwest IL and the temps have been in the 20's during day. I have been burning straight #2 with the Lucas lubricant and Power Service for anti-gelling. I have been looking for Stanadyne, but have been unable to find it anywhere.

I have my fuel pressure sender before the filter on the incoming port of the fuel filter canister.

Thanks for your help.

Dan

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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

 

[John]

You can order all Stanadyne products from D. I. S. (Diesel Injection Service).

 

[Whitmore]

Dan, just a thought I would want the psi to be read at the after filter that way you know when your filter is getting pluged, better yet install a switch and then you can read the differential pressure, my o2

Kevin 2001 eth dee

 

[Steve Campbell]

There was another thread talking about lift pumps that said one of the symptoms of a failing pump was a stumbling/hesitation when letting off of the throttle after a hard acceleration/pull. Another thought, could this be a wiring problem (connection or ground)?

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1999 Qcab 4x4 Driftwood
Steve

 

[John]

I don't think so BZIN/UL... the owner of The PowerShop found the same condition present on Rams he has diagnosed. This was discussed in the latest issue of Western RV (Nuts 'N Bolts column... written by Chuck Arnold. . the owner of The PowerShop).

 

[ROAD WARRIOR]

I don't believe that it is a wiring problem. When I first installed the sender and gauge, I checked for good continuity to ground at both ends. After getting the strange readings, I grounded both components at the same point to eliminate any possible loops. No change. I think Chad is right in that once the truck is warmed up, it doesn't seem to change. Except mine will occasionally after a quick on-and-off of the throttle. And when this happens I never notice any engine stumble. Even at idle when it is cold and it is screwing up, I don't get any stumble.

Where can I purchase the Lubricating Engineers DCI+? Is this as good as Stanadyne or Howells?

Thanks for your help.

Dan

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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

 

[strick]

Hey ROAD WARRIOR. I have a SW(liquid) guage that does the exact same thing. My fuel line is clear so I can see the air bubbles in the guage line after a few minutes the fluctuation goes away. It scares the He!! out of me when it does it. You have 10psi at wot? #ad
Wow! I only get 10psi at idle. WOT I might get 1-2 psi. Heavy pulling 3-5 unless I pull a hard hill. Normal cruising is 6-7 psi. I think I need to go buy my a new lift pump from cummins! If you are getting that good pressure I might not fool with tricking out the lines and putting a Mallory pump on. What does everybody think. Are Road Warriors pressure readings his good luck or are my pressures my bad luck. I've got hauling jobs coming up shortly. So I would like to hear some responses. Jason

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'99 3500HD flatbed, 5 spd 4:10 Posi, homebuilt underbody toolboxes & cowcatcher, 4" down w/straight stack(speak-up! I can't hear you!), K&N filter, what silencer ring? mudgrips, banks pyro & boost guage, sw fuel guage, 50% 3 wire BlueBox(HOLYSMOKE), Psycotty air, PS boost module w/ elbow, thinking about 1/2" fuel lines(real hard)
Jason

 

[Chad Sheets]

You will have air in the line to the gage. It works that way. If you have ever hooked an oil psi gage up you will notice the actual oil doesnt make the gage move.

The "guts" of the gage acts like a thin rolled up hose. When the engine is running, it forces the fuel through the line to a thin rolled up hose, which then will eventualy register a reading. Once fuel psi is brought up, the thin hose starts to roll back out flat (like a garden hose does when the water is turned on) inside the gage causing a fuel pressure reading reading. The hose is called a "bourdon tube". It moves a pivoting link, which moves a pinion gear which ultimately turns the dial on the face of the gage for you to read.

At any rate, your fuel psi readings are "normal". About 10 at idle. About 7 going down a nice flat road. About 4 hauling a$$ or pulling a BIG load.

"They" say its normal, but I will be investing in a Mallory elec pump this Spring. I hear that you never see more than 15, and never less than 10. Thats what I call perfecto!


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Always ready to help!
2000 2500 Red Sport quad cab, 4x4, K&N, DDI's, straight piped, boost, pyro and fuel pressure gages, Hot Power Edge, mean looking set of 33. 5" tires, Snap On diamond tool box, Marine Corps window sticker, Semper Fi!

1972 340 Cuda'. Original tripple Black, 340 car w/air. Good clean car, super stock springs, Weld Prostars, shaker hood, strong 340 with a 727/4000 stahl, 4. 56... . Bombs away!
NRA Life Member. http://www.geocities.com/chadsheets