Low fuel pressure, reduced engine power

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Apr 26, 2021 | 08:50 AM

davearx

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5th Wheeling

Joined: Apr 2003

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From: LAWRENCE,KS

Low fuel pressure, reduced engine power

I could use some help please. Yesterday coming home from camping pulling camper got low fuel pressure, reduced engine power warnings. Pulled over, crawled under truck and open water separator drain. Air hissed into the fuel conditioner module. Truck started and ran without warnings. 23 gallons on fuel in 56 gallon S & B tank.
Any ideas would be welcome. There was a slight hum yesterday that is gone today. Thanks, Dave.
PS 2016 F350 62,000 miles

Apr 26, 2021 | 11:35 AM

djousma

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From: West Michigan

Sounds like a tank vent isnt working properly, developed a vacuum that the pump couldnt overcome and cut off fuel.

Apr 26, 2021 | 11:37 AM

Just Strokin

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From: Tallassee, ALabama

Sounds like you have air in the fuel system. You can try cycling the key from Off to On (not start) to see if the fuel pump can purge the air as you would do if you changed filters.

Did you recently change fuel filters? If yes, check to make sure you have the cup on the frame pump/filter screws on till the stops on the cup and pump/filter housing meet.

You might have to purge the air from the fuel system. The procedure has been posted here. Do a search for fuel system purge or purge.

Apr 27, 2021 | 06:58 AM

Overkill2

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From: Western NY

Curious... Following.

Apr 27, 2021 | 07:53 AM

davearx

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5th Wheeling

Joined: Apr 2003

Posts: 46

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From: LAWRENCE,KS

Thanks for all the replies. Vent line chased and clear, filters 3000 miles old, changed every 10,000 miles. I was hoping to not to have to drop tank. Could I follow the fuel line pressures with forscan? Thanks, Dave.

Apr 27, 2021 | 08:57 AM

mjs2011

Tuned

Joined: May 2019

Posts: 279

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From: Brookings, SD

When you say you opened the water drain valve and heard air whoosing in, was it really air being sucked INTO the water seperator drain, or was air blowing out?

As for lift pump pressure, yes you can watch this with Forscan, either the PC program or Forscan Lite on your mobile device. Lift pump pressure should be around 80 psi for your truck if I recall correctly.

Apr 27, 2021 | 09:25 AM

djousma

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From: West Michigan

Quote:

Originally Posted by davearx

As someone else mentioned, if you literally determined that air was being sucked in, it can only be one thing....something at the tank end is plugged. I suggested the vent, but it could be possible that you might have dropped one of those little cardboard inserts from fuel additive containers into your tank? Its an issue because the petroleum nature of the additive breaks down the adhesive that holds those little cardboard in, especially if you reuse them. More than one person has and causes intermittent problems like you are having. Those are about the size of the fuel pickup in the tank. When you released the pressure and cardboard fell away from the pickup tube and away you went again.

Forscan is only going to measure fuel rail pressure, and probably the DFCM pump pressure. that is not where your problem is. you dont want to be starving the HPFP of fuel, as that is the lubrication for it too.