Medium and Heavy Trucks
Have Truck Repair Questions? Ask an Expert
Hi John sorry for delay,
Fuel in oil can be cause by fuel pump, injectors or injector o-rings, cracked head.
Most common cause of this issue is the fuel pump leaking past front seal into crankcase causing all your other issues.
They do sell a dye you can add to fuel and run engine then use a black light to find leaking injectors or o-rings, then if they where not leaking you remove fuel pump and look for traces of dye around pump drive.
Click here for dye kit
one other thing, only if you have stc injectors the control valve on drivers side of block at the rear can leak fuel into oil.
The control valve uses fuel and oil to control injector timing.
Please don't forget to rate with stars so I get credit for my time.
Let me know if you have any questions, rating does not close question