Hello I own 1997 Ford L 9000 with a 425 cat all mechanical my problem is the run really good no smoke but underpowered turbo boost used to be 25 and now it's down to 15 on flat highway goes about 80 miles an hour as soon I it a small hill it drops down to 50 I hear the turbo kick in I check for air leak no leak change all filter does somebody have subjection I appreciate it thank you
I have seen the fuel solenoid not move completely, limiting power.
Sounds like a fuel problem. Could be injectors. Did you check air filter?
Good odds it's the fuel filter, after that check the air filter and the air-to-air. Then it gets tougher.
don't forget to visually inspect the turbo
Air/fuel ratio diaphram?
Partially stuck open waste gate on turbo? Air leak between turbo & intake?
Smoke? No smoke?
Well if you put on a new fuel filters, I would say collapsed fuel line from tank to pump. Any other symptom you would get smoke if it was fueling. Obviously not getting fuel.
Get a fuel pressure gauge on it first. Should be 32 psi or better. If it's low check fuel supply and transfer pump. If fuel pressure is ok test air fuel ratio control next. Then check turbo exhaust wheel and mounting divider web. Then pressure test the aftercooler.
I second this! Change the diaphragm.....TIO
Thank you guys for your help problem is fixed it was the air/fuel ratio diaphragm and A Spring was broke and thank you again guys appreciate it
Good job! Sometime these trucks can drive you crazy.