95 460 lean under load
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95 460 lean under load
I am the new owner of a 95 f250 5 speed with a 460. I have been tuning the truck up with fresh coolant, cap rotor, plug wires, plugs etc.
I Have only driven the truck about 70 miles but the big hills near me have exposed how the truck runs lean climbing hills, enough to make the truck buck slightly especially under partial throttle. Scanning it I did get a lean code and all the plugs were slightly white when changing.
for for what I have triedFuel filterRepairing butchered wiring to tank selector switchFuel pressure regulatorThe fuel pressure at the rail is right at the bottom of the spec (with both old and new regulator), 30psi at idle and 35-38 with vacuum disconnected. I figured it couldent be the pumps as it runs like this from both tanks. However I did finally test the rail pressure on the rear tank and it was maybe 1-2 psi below the rear tank pressure.
could both pumps be low on power simultaneously? Please talk me off a ledge here!
Thanks
I Have only driven the truck about 70 miles but the big hills near me have exposed how the truck runs lean climbing hills, enough to make the truck buck slightly especially under partial throttle. Scanning it I did get a lean code and all the plugs were slightly white when changing.
for for what I have triedFuel filterRepairing butchered wiring to tank selector switchFuel pressure regulatorThe fuel pressure at the rail is right at the bottom of the spec (with both old and new regulator), 30psi at idle and 35-38 with vacuum disconnected. I figured it couldent be the pumps as it runs like this from both tanks. However I did finally test the rail pressure on the rear tank and it was maybe 1-2 psi below the rear tank pressure.
could both pumps be low on power simultaneously? Please talk me off a ledge here!
Thanks
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Fuel pressure would have been my first guess but those pressures look acceptable, you should probably still figure out some way to monitor it while driving to see if the pumps have a volume problem.
Any evidence fuel is being transferred to the inactive tank?
Yoiu could also try disabling EGR, just disconnect and cap the vacuum line at the valve and take it for a drive.
Any evidence fuel is being transferred to the inactive tank?
Yoiu could also try disabling EGR, just disconnect and cap the vacuum line at the valve and take it for a drive.
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Pulled the EGR vacuum and capped it. Maybe it runs better. Interestingly it is possible that the rear tank is returning to the front as the full tank became near empty from very little driving and lots of idling. I filled both tanks today and the front was reading empty and only took 6 gallons, filled it still reads empty. Truck definitely runs poorer on the front tank, (a little hesitation, rougher running).
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Good chance you have the fuel transfer problem, that bleeds of some volume that should go to the motor... potentially enough that the motor would be down on power.
The fuel level sender in your front tank is dead, the pump is weak, and the check valves that should prevent crossflow aren't working either so you may as well drop that tank and replace the whole FDM.
The fuel level sender in your front tank is dead, the pump is weak, and the check valves that should prevent crossflow aren't working either so you may as well drop that tank and replace the whole FDM.
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New User
Joined: Aug 2021
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Good chance you have the fuel transfer problem, that bleeds of some volume that should go to the motor... potentially enough that the motor would be down on power.
The fuel level sender in your front tank is dead, the pump is weak, and the check valves that should prevent crossflow aren't working either so you may as well drop that tank and replace the whole FDM.
The fuel level sender in your front tank is dead, the pump is weak, and the check valves that should prevent crossflow aren't working either so you may as well drop that tank and replace the whole FDM.
Thread Starter
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New User
Joined: Aug 2021
Posts: 4
Likes: 0
Good chance you have the fuel transfer problem, that bleeds of some volume that should go to the motor... potentially enough that the motor would be down on power.
The fuel level sender in your front tank is dead, the pump is weak, and the check valves that should prevent crossflow aren't working either so you may as well drop that tank and replace the whole FDM.
The fuel level sender in your front tank is dead, the pump is weak, and the check valves that should prevent crossflow aren't working either so you may as well drop that tank and replace the whole FDM.
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FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Have you pulled the codes lately? The TPS could have a flat spot that is generating that partial throttle problem, somtimes this sets a code sometimes not, worth a look either way.
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