Engine/Transmission (1998.5 - 2002) Fuel Pressure making me crazy!!!

[Grizly]

Got a question that is driving me nuts: Bought edge w/att. now having fuel pressure guage for past 6 mo. pressure is all over sooo I bought x 2 new l/p and bought valcan big line 1/2 all the way w relocation of pump and then got draw straw went intotank still when truck warms up idle / low throttle is 8-10 but when I throttle up about 20-25 percent pressure is 14-17 but at w/o/t is about 11-12? I can't think what else to do... . any help would be nice, PLEASE Help...

 

[mhenon]

It's the sending unit. Mine was all over the place and that was the problem.

Mike

 

[EGaskamp]

Is the gauge making a vibrating noise? Or is the needle going back and forth really fast? If so try putting a needle valve on the line. Thats only if it's an instermentation problem. Good luck

 

[Diesel Dummie]

Sounds normal to me,cold fuel will flow a little slower than warm fuel, but it sounds ok to me, i put in aholley blue back by my tank and i see 25-27 at idle,nol ess than 17 at WOT.

 

[Grizly]

fresh start cold pressure is steady 16 - 17 till 20 min after driving then at no throtle pressure is at 8 - 9 psi but then when I throttle up 20 percent presure returns to 15 - 16 but if I go 60 - 70 percent throtle it goes back down to like 11 -12 psi that part is ok to me but the 8 - 9 psi at idle is what I don't like and makes no sense to me ... . Ooo and my guage is built in to the Edge w/Attitude display and pressure is checking at main puel pump vp44 inlet 1/2 elbow 1/2 line from vp44 to the filter and then 1/2 from filter to the l/pump near fuel tank then in line filter then 1/2 inch line to Draw straw 1/2 to the bottom of tank.

 

[Cummins724]

fresh start cold pressure is steady 16 - 17 till 20 min after driving then at no throtle pressure is at 8 - 9 psi but then when I throttle up 20 percent presure returns to 15 - 16 but if I go 60 - 70 percent throtle it goes back down to like 11 -12 psi that part is ok to me but the 8 - 9 psi at idle is what I don't like and makes no sense to me ... .

I bet you have air in the line that goes to the fuel gauge. Do you have a isolator?

 

[Grizly]

little more info please, isolator? just used what came with edge kit? elbow with npt fitting to go to the electronic sensor with three wires going to it. . don't want to sound dumb but I can thing of other mods to spend money on but want this fuel pressure problem fixed first. never had to change vp44 but that was only thing left other then after maket l/p

 

[Grizly]

Updated sig a little bit.

 

[Cummins724]

I'm sorry... I didn't catch the juice with attitude. I thought you had a mechanical gauge. The readings are probably a fault in the attitude or the sensor.

 

[Cummins724]

Isolators are a mechanical device that goes inline between the fuel line & fuel gauge. It takes fuel in on one side & converts the pressure of the fuel into the other side. . . which is filled with antifreeze. The idea is that it is safer to have antifreeze in your truck than raw fuel incase of a leak.

 

[LBello]

mine does make alot of noise. It started losing pressure from 19 to 14 now. never lower than 11. It also starts a whole lot better since the pressure drop.

 

[mhenon]

It's the sending unit. Mine was all over the place and that was the problem.

Mike

I said sending unit... I meant isolator. Mine had leaked the anti-freeze and was full of air. The pressure readings were just whacky.

Bled the air out and all's well.

Mike

 

[Grizly]

Wel Thanks guys I will try to bleed again hope for the best, driveway smells like diesel allready wife dislikes it but how ya gonna catch all that fuel: I may call edge and ask them to send me new pressure valve should still be under warenty I hope for a Paying thousand dollors for it I would get a warenty with it!

 

[Grizly]

What happend to my sig?

 

[C.Solomon]

My fuel pressure does the same thing, I also do have a sending unit. The lift pump acts like its a load sensitive. I can be at idle and see my pressure drop to 10 lbs. I apply a load on the engine and fuel pressure will go back to 15lbs, and be normal for hours if I keep a load on the enigine.



I can't see how a sending unit could be causing it.

Its a very weird thing but as long as I have good psi while driving I can live with it.

 

[Grizly]

I agree but edge comes with set able alarm on attitude monitor and I have it set at 10 lbs I don't want pressure any lower then that and that should be good but I want it all I guess. never seen any post about low pressure at idle only so Thought this was wiered.

 

[PC12Driver]

I've had a lift pump fail this way. At low flows (idle or rolling to a stop) my pressure would drop to a steady 8-9 psi and it would come back up to a normal 14-15 psi after I gave it a shot of throttle. About the best I can figure is that the vanes in the pump are stalling out in the fluid, and then once the flows come back up the pump can "bite" into the fuel again and get a good push. A new pump fixed this one for me.



If there isn't an isolator, you really don't need to bleed an electric sender. The fuel in the line will compress the air to whatever the fuel pressure is and you'll get a true reading (you can not have two different pressures in a common sealed vessel) In fact, leaving the air in will probably give a smoother reading, since the air will act as a cusion and smooth out the pulses.

 

[PC12Driver]

What happend to my sig?

It only shows up in your first post of the thread.

 

[Grizly]

Thanks again guys, I have talked with edge people and they are sending me new pressure sensor and I will order new pump again and see if this helps maybe I will get after market l/p just did not want to spend that much money but have allready done that/ looks like gone too far to back out now!!!