Possible injection pump trouble
 

Okay,I love my truck,but this is driving me crazy trying to figure out.I have an 86 F250 XLT...6.9l idi...118,000 miles on it.Starts & runs beautifully,for a couple of miles,then I can feel the engine "kick down & start running rougher and starts blowing blue smoke.Until it does this,it runs fine.Im no expert on diesels,is there a solenoid in the injection pump,or something simple I'm missing.I haven't taken it to my local mechanic yet due to money.I change the oil,fuel filter,air filter when I'm suppose to.Drain the fuel/water separator.Any help would be appreciated.

Warm up solenoid is bad ... I believe it's drivers side of pump and it's cheep..