I have a Ford 7.8 liter engine in my 1992 Ford dump truck, it has always been underpowered struggling to pull tag trailer up a slight grade with 12000 or 30000 pound machine on it. It is a 225 HP engine 605 ft lb torque. mileage on the engine 101,000; its second engine - 254,000 on frame. Transmission is Fuller 10 speed (8 speed with 2 low low). This year the clutch was adjusted a few weeks back, throttle pull back spring replaced, thats it this year. After fixes engine worked as it has for last 10 + years. Last week the engine was transformed, a miracle. Now out of the blue the engine has huge horse power and torque! I can accelerate up a slight grade with the equipment tag trailer that I had to down shift traveling up the grade before last week. I have to be careful not to rev the engine over the 225 HP 2300 rated speed rpm;the engine now just accelerates up the RPM curve; the high idle speed is 2680/2760 RPM. Does any one have any idea what has happened to this engine? Would really appreciate your thoughts. Thank you.
I have a '91 F800 with a 7.8 and never had anything like that happen, did the throttle spring replacement reset th throw on the pump lever? Mine had a worn out overtravel spring on the pump arm that I replaced and made a bit of a difference in power.
The throttle travel is the biggest part of an engines power "problem".. Just have someone push the pedal to the floor & check it.. its supposed to hit the stop screw.. Just about 75% of them DONT.. On some trucks, theres a stop bolt behind the pedal itself, that can be adjusted DOWN OR the linkage at the pump can be adjusted.. AND.. if you really want more rpms, the stopper bolt on the pump can usually be turned IN 1 turn.. without touching the internal governor.. BUT you can go TO FAR & actually decrease the rpms..{internal gov.}
The increased power is through the entire throttle movement from just a little depressed pedal to the high 2300 rpm. Through out the RPM range there is considerable more power. It wonderful to have all this power I just am wondering why its happening. Any one know?
Believe it or not it could be fuel filters plugging up. I laughed the first time I was told that but whenever my 7.8 had an increase in power thats what it was. Power went up and fuel mileage dropped. My cousin used to work at a Case IH dealership and he told me when they would bring a tractor in they would dyno it first before working on it. Then after doing a complete service and tune up they put it on the dyno again and it would have less horsepower than before. A fuel injection guy told him that Bosch & Nippondenso inline pumps will actually put out more if the fuel inlet is restricted. I'm sure others will comment on this.
Maybe one of your employees knows a little bit about turning up the fuel to your injection pump.
We've got 3 Ford 8000 trucks with 7.8L Ford and Allison auto trans. None are a slouch, but they also only run at 50,000 pounds loaded. We had one start to run really sluggish this summer and took it in. Ended up being a chunk of alfalfa haylage sucked into the fuel supply line. Took the line off, blew through it.backwards and voila! Truck runs great again. But when the fuel was restricted, it ran like crap.
I have changed the fuel water filter and the engine settled down. Thank you, never would have thought of that, much appreciated.
I know, it seems backwards. Glad it worked out.
Crazy. Putting that little tidbit of info in my brain compartment.