3126 Cat started dumping big smoke!
 

we have a freightliner fl70 truck with a 3126 cat, it has around 100,000 miles on it. we had it out using the crane and it cut out and started missing badly and smoking gray fuel smoke very very badly. is their a common problem with these engines? i dont know if it is just an injector failure or computer problem, but it does have a fuel knock sound and my 12v pullin truck doesnt smoke as much as this thing is now!
any help would be great! thanks