Low Fuel Pressure

Jmoore1225 · Aug 14, 2012

Had this happen today.... Truck fell on its face from a hard roll into out of a turn :-/

B585Ford · Aug 14, 2012

Dustball8504 said:
I didn't know you could bump the factory regulator. Would that help running the higher tunes?

I'm no expert, just trying to help by sharing what I read from someone who knows more than me. I am pretty sure he explained how he raised the pressure in that thread.

Smokyred · Aug 14, 2012

B585Ford said:
I'm no expert, just trying to help by sharing what I read from someone who knows more than me. I am pretty sure he explained how he raised the pressure in that thread.

He just said he stretched the spring out, and that you have to be careful taking it apart because it is not designed to be serviceable.

Dave

Dzchey21 · Aug 14, 2012

Im not sure more low pressute fuel is tge answer anyway. Checking to make sure there is positive pressure at the time of shutdown is what is important. Ford pumps dont really seam to care how much pressure they have as long as they are not in a vacuum.

That being said my last trip ti the track I was having issues with my truck acting like it was out of fuel but it was in the tuning because I loaded an old gearhead tune and it fueled fine... unsure why at this point

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Wayne · Aug 15, 2012

I did adjust the spring, and as stated above it's not supposed to be servicable. factory low pressure spec at idle is 4-7, and I got mine up to 5 by streching the spring. It read 2.5 before I did anything. It didn't help much as anything above 3/4 throttle causes it to drop off to 0, or possibly a vacuum. I just don"t know though without a vacuum gauge. The problem I have is a crappy pump, and now I have a higher pressure for it to fall off of. I think it helped a bit, but it really just needs a new pump. Who knows? I might be able to maintain, or come much closer to maintaining rail pressure with my current pump with the X race programming.

mortal798 · Aug 15, 2012

Dzchey21 said:
Check low pressure fuel first should maintain around 3 psi all the time at the cooler

Put a digital fuel pressure guage on it and drive it around. My lpfp was going out and it would start out 4.1psi, 4.5psi, then on accel it would drop to 0.7psi. Sometmes it would quit, but it always stored codes.

Replaced lpfp, problem solved.

Dzchey21 · Aug 15, 2012

mortal798 said:
Put a digital fuel pressure guage on it and drive it around. My lpfp was going out and it would start out 4.1psi, 4.5psi, then on accel it would drop to 0.7psi. Sometmes it would quit, but it always stored codes.

Replaced lpfp, problem solved.

I had the same problem awhile back and I ended up just using an air dog but same difference. Now I maintain around 7 at the elite air dog block so I haven't really looked back

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drservo · Aug 15, 2012

Dzchey21 said:
Im not sure more low pressute fuel is tge answer anyway. Checking to make sure there is positive pressure at the time of shutdown is what is important. Ford pumps dont really seam to care how much pressure they have as long as they are not in a vacuum.

That being said my last trip ti the track I was having issues with my truck acting like it was out of fuel but it was in the tuning because I loaded an old gearhead tune and it fueled fine... unsure why at this point

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Mine does it with Spartan or Gearhead tunes, its just not consistant sometimes it runs fine. My dealer is cool with my mods and I'm still under warranty, just need trying to know what to tell him to look for.

drservo · Aug 28, 2012

Tech says the new flash will take care of this, says hes had a couple do this and the flash fixed it. Anyone know? Will the new flash not be overwrote when I reprogram it back?

Jeff@Spartan · Aug 28, 2012

The new flash raises the fuel rail pressure high limit from 25,000 to 27,000 psi. I assume that this new parameter is only going to be valid with the stock file loaded. It's not going to be there once a tune is loaded. My personal opinion is that Ford is doing this so they can avoid replacing pumps until the pump completely goes. Makes diagnosis easier and they don't have to replace as many pumps that are still under warranty.

Wayne · Aug 28, 2012

For what it's worth, Today I dynoed on my stock lift pump, swapped over to the air dog DF 165, and re-dynoed. The switch took all of 10 minutes as all the lines and wires were run, I just had to un clip, and re-connect 4 fuel line fittings, install a fuse, and pull the power supply to the stock pump.

Back to back dyno runs provided 0 gain in power or rail pressure, but I was able to maintain a minimum supply of 7 psi as opposed to 0, if not a small vacuum. I'm sure the lack of pressure contributed to the inability of my injection pump to maintain pressure, but the damage is done. Now the next group of mods on the list include 60 hp nozzles, and a pump that will maintain them. No looking back now. I'm tired of fuel pressure limiting me.

riest:Moral of the story: Don't let your weak lift pump kill off your injection pump. FWIW, my injection pump has only about 80K miles, but has probably had a weak lift pump it's entire life. 177K total on the truck now.

B585Ford · Aug 28, 2012

Wayne said:
For what it's worth, Today I dynoed on my stock lift pump, swapped over to the air dog DF 165, and re-dynoed. The switch took all of 10 minutes as all the lines and wires were run, I just had to un clip, and re-connect 4 fuel line fittings, install a fuse, and pull the power supply to the stock pump.

Back to back dyno runs provided 0 gain in power or rail pressure, but I was able to maintain a minimum supply of 7 psi as opposed to 0, if not a small vacuum. I'm sure the lack of pressure contributed to the inability of my injection pump to maintain pressure, but the damage is done. Now the next group of mods on the list include 60 hp nozzles, and a pump that will maintain them. No looking back now. I'm tired of fuel pressure limiting me.

riest:Moral of the story: Don't let your weak lift pump kill off your injection pump. FWIW, my injection pump has only about 80K miles, but has probably had a weak lift pump it's entire life. 177K total on the truck now.

Thanks for the update. At least IMO, this info is invaluable.

Tree Trimmer · Aug 29, 2012

where are you checking pressure at, on the lpfp, so i can tie into mine, and check it as well.

is there a simple place to do it, or is it just break a line and tie into it.

WoodBoy · Aug 29, 2012

Monitoring with the dashdaq Ive been driving about the same 1/2 throttle or so when it hits OD it will set off the alarm for low frp that is set at 4700ish for a sec. Gearhead Hot street

Wayne · Aug 30, 2012

Pressure is measured at shrader valve off of the banjo fitting at the front of the fuel cooler.

drservo · Aug 30, 2012

Dealer flashed yesterday and mine hasn't dropped yet but we'll see how long it lasts.

madman1234509 · Aug 30, 2012

Wayne said:
For what it's worth, Today I dynoed on my stock lift pump, swapped over to the air dog DF 165, and re-dynoed. The switch took all of 10 minutes as all the lines and wires were run, I just had to un clip, and re-connect 4 fuel line fittings, install a fuse, and pull the power supply to the stock pump.

Back to back dyno runs provided 0 gain in power or rail pressure, but I was able to maintain a minimum supply of 7 psi as opposed to 0, if not a small vacuum. I'm sure the lack of pressure contributed to the inability of my injection pump to maintain pressure, but the damage is done. Now the next group of mods on the list include 60 hp nozzles, and a pump that will maintain them. No looking back now. I'm tired of fuel pressure limiting me.

riest:Moral of the story: Don't let your weak lift pump kill off your injection pump. FWIW, my injection pump has only about 80K miles, but has probably had a weak lift pump it's entire life. 177K total on the truck now.

I want to see this but now with the fuel bowl deleted...... I want to see if there is any real restriction with it and if it will cause lower rail pressure, and if there is any gain. See if all of the hype about the elite airdog mod is what its cracked up to be....

713Diesel · Aug 30, 2012

madman1234509 said:
I want to see this but now with the fuel bowl deleted...... I want to see if there is any real restriction with it and if it will cause lower rail pressure, and if there is any gain. See if all of the hype about the elite airdog mod is what its cracked up to be....

I would like to see that as well. The upgrade is six hundred bucks right? I know it is a good idea and all but for us guys that don't want to go more than just your simple tune CAI and exhaust is it really worth it? Per this thread it sounds like it is a good idea to go ahead and get the airdog for the sake of your hpfp but are we gaining any more power or reliability with the upgrade kit? And for the record I am actually asking the question I am not hinting one way or the other.

Wayne · Aug 30, 2012

The airdog upgrade is mostly for guys running larger injectors, and guys who need the space where the fuel bowl sits. Only a small gain will be had on trucks with stock injectors. When you have enough fuel demand to suck down the pressure at the factory shrader valve below 4 psi then it's a definite need since there's more flow and regulator control with the upgrade. The extra filter is also redundant, and unnecessary so it's a plus to get rid of it for that purpose.