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Hello everybody, so my problem is my truck sound rough on throttle up especially under heavy load. Barely hear it on neutral throttle up, more on driving empty, extremely when pulling trailer. When I moniter psi on rail it is erratic even on idle jumps 1800 psi up or down on idle. Throttle up in neutral sometimes 3000 psi difference from desired psi. On scan tool the psi on rail is always very sloppy no matter in what position the truck is. But I can hear it more physically when fuel demand is greater. When coasting at 70mph I can’t hear it but pressure still erratic. I have changed Regulator 1. Seemed to make it better for 100 miles but no more. Checked the wiring looks great. Stopped engine shows shows 250-300psi could this be my pressure sensor, any suggestions would be greatly appreciated.
 

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What codes do you have?
 

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So when you say you changed the regulator, you're talking about the FPR on the injection pump? Not the relief valve on the fuel rail? If so, was there any debris on the regulator screen? A few tiny bits of metal on the screen would mean the pump is failing. LML's are pretty famous for it.
 

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Ouch, I mean ok, at least you don't need a new fuel system. That's good but it was the most obvious answer. Now it gets tougher.
 
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