Had a broken rocker arm afterwards the motor seems to have no power no go and there's white smoke coming from the tailpipe there is absolutely no power I can't even get it to accelerate above 10 mph

What did you do to fix the broken rocker arm? What other work was done? Were the heads removed and the valves and valve seats checked? Is the timing set correctly? Are the valves set correctly? The white smoke: is there water vapor in the tail pipe? Are you losing water from the radiator? How many miles do you have on the truck?

my diesel truck doesn't start I have a 6.6 2004 Chevy Silverado 3500 4x4.when I started it cranks start up and shuts off

aochoa1975: This has to be a fuel flow issue. If it starts, then the glow plugs work, the fuel gets into the cylinders, but afterwords, it is fuel starved and it shuts down. You may have a clogged fuel line. Check all the fuel line filters, even have the jets cleaned. Last resolve is to check the fuel tank itself for any old fuel residue. After 10 years, the chance of having the paraffin in the old fuel separate is good. Some old fuel tanks from stations may not sell enough diesel fuel to keep the contaminates out of the tanks. Then they may not change filters often enough or keep fresh fuel in the holding tanks so the old fuel breaks down.