Low Fuel Pressure

drservo · Jul 3, 2012

What causes this? At 3/4 to full pedal fuel pressure drops at least below 4500 (thats where I have a warning set at) truck completly dies for a second then picks back up. Been doing this for a long time, only does it on the high HP tunes, Spartan 275 and 310.

White_monster · Jul 3, 2012

Any codes?

drservo · Jul 3, 2012

Nope, no codes

O2ShootTheJ · Jul 3, 2012

When was thrblast time u changed your fuel filters?

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Jeff@Spartan · Jul 3, 2012

Does this happen while going through the gears (specific shift) or once the transmission is in O/D with the converter locked?

Corb@CorbinShipping · Jul 3, 2012

drservo said:
What causes this? At 3/4 to full pedal fuel pressure drops at least below 4500 (thats where I have a warning set at) truck completly dies for a second then picks back up. Been doing this for a long time, only does it on the high HP tunes, Spartan 275 and 310.

How many miles do you have on her? I did something similar at around 75,000, and my low pressure fuel pump chit the bed. would idle, and run ok if I was easy on her, then, the next day, as soon as I touched the pedal, she fell on her face, and then wouldnt even start. Pulled 19 ohms on the resistance tester..... D E D, dead... But it took a few days to get to that point...

drservo · Jul 4, 2012

48k on the truck, just changed the filters last week. Only does it going through the gears never does after the converter is locked. Runs great other than that.

Jeff@Spartan · Jul 4, 2012

I'm thinking it could be a transmission defuel but the 310 tune shouldn't defuel for the transmission. The 275 tune is the highest tune to defuel for the transmission.

Rene G · Jul 5, 2012

Mine just started doing this today, subscribed to see what happens.

Beans71086 · Jul 5, 2012

Ok, so mine does this only with the newest tunes, the only one ive run is the 310, at about 1/2 to 1/4 throttle, when it shifts into OD (converter locks) it dies for a split second then comes back right away. Same thing as his, rail pressure drops to about 4-4500.

08twinturbo · Jul 8, 2012

I have had this same issue on quite a few trucks tuned with the earlier spartan 275 with the 45mph lock. I was always told it was the truck defueling sensing tranny slip. I never had any problems on any other tunes including the 310.

madman1234509 · Jul 9, 2012

Mine would do this with the 310 early lock, same thing, 1/2-3/4 throttle or so. Shift into OD and it would fall on its face, rail pressure drops to 4-4.5k. I ran this tune for the last 3 months and it never started doing it until a week or so ago. I also watched my rail pressure at WOT with the converter locked on the 310 and I have only holding like 23k psi rail pressure. So I wouldnt doubt if it was my lpfp crapping out. Changed to 300 and 275 late lock and it seemed to stop. I also have 103k....

Jeff@Spartan · Jul 9, 2012

Sounds like a fuel system issue, especially if it's coming out of no where.

drservo · Aug 14, 2012

Does the cab have to come off to replace the HPFP? Mines getting worse, it does it anythime I run WOT and has done it a few times while towing. It should be the HPFP and not the LPFP right?

Jeff@Spartan · Aug 14, 2012

Pulling the cab makes it much easier.

2008SleeperStroker · Aug 14, 2012

I had same problem. Change filters and it was fine for a bit then went back to loosing pressure. Finally got angry enough and spent the money on an Airdog 165. Bes $600 dollars spent. Solved my rail pressed issue and now have better mileage by 0.5 and better filtration.

B585Ford · Aug 14, 2012

drservo said:
Does the cab have to come off to replace the HPFP? Mines getting worse, it does it anythime I run WOT and has done it a few times while towing. It should be the HPFP and not the LPFP right?

I would want to know for sure before I spent the money to replace HPFP. Granted the HPFP will eventually fail, but if you can get another 50k miles out of it, no sense to replace it now if it doesn't need it. According to Wayne from another thread, he said he bumped the regulator pressure from 2.5 psi to 5 psi on the factory regulator. His pressure source for the testing the LPFP was the factory schrader valve on top of the fuel cooler. Ight consider trying that before buying the HPFP.

Dustball8504 · Aug 14, 2012

B585Ford said:
I would want to know for sure before I spent the money to replace HPFP. Granted the HPFP will eventually fail, but if you can get another 50k miles out of it, no sense to replace it now if it doesn't need it. According to Wayne from another thread, he said he bumped the regulator pressure from 2.5 psi to 5 psi on the factory regulator. His pressure source for the testing the LPFP was the factory schrader valve on top of the fuel cooler. Ight consider trying that before buying the HPFP.

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

Dzchey21 · Aug 14, 2012

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

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F350 Stupid Duty · Aug 14, 2012

I'm having the same issue. Comes and goes - basically it will last a couple weeks then it goes away... Occurs when I'm lightly accelerating/hovering just below the shift point and then shifts into OD. Does not happen when I'm steadily accelerating through the shift point or WOT. I lowered my FRP warning to 3000 psi and it would reach it. Basically as soon as it shifts the FRP blips below the lower limit then immediately recovers.

I have heard about the VCV (volume control) and PCV (pressure control) as being potential culprits but I have to purchase additional "licensing?" through Drew Tech to monitor them.

I'm running the 310 EL. Happened with the old tuning (enc files) and the factory trans and now the Suncoast trans.