Tunes, parts and Mpg
So I have this 07.5 that I've been fight a rail pressure code issue. I have changed almost every thing in the fuel system for different parts and it still sets the low rail pressure and low lift pump codes daily. Something I have noticed was when the truck had the original 400k mile parts on it, I would get 18-19 mpg on the highway just the truck by itself. So as I've switched the injectors, cp3, rail plug, ect. I'm now down to 13-14 mpg highway. I've not changed the tune and fuel pressure is 14-15 psi which FASS says is fine. Anyone else ever had this drastic of a drop by swapping stock parts for stock parts?
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Yes,rail plug is leaking under higher pressures. Sand the rail plug flat and install a copper washer under it then crank it down
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Have you checked the FCA harness? Mine was setting high rail pressure, and was commanding 100% due to an internal wire problem. Might be worth the $17 for the replacement piece.
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I’m curious about the plug and/or connecting tubes.
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I've had that happen it's several things. Old injectors were worn and injecting more or less fuel than stock. PRV may be malfunctioning letting pressure by. and then Fuel pressure sensor has been found to cause havoc! Is the truck defueling when the CEL comes on?
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This sounds like aerated fuel to me. Does it always start like it should?
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I assume new CP3. And the return banjo on the back of the head? But like Biggy said if it's sucking air that would cause it but I'm sure your gonna say it has a sump! So maybe do a bucket test on the returnsee if it's aerated.
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My bet is a leak between rail and relief valve. I've now had several high mileage rails leak there.
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Big bubbles not ok Sent from my XT1575 using Tapatalk |
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