Nissan Repair: Nissan D22 diesel smokes, nissan d22, fuel pressure regulator

Question
Hello,

I have a 1998 Nissan d22/pick up it has a 2.5 diesel engine. It always starts, ticks over smoothly & 90% of the time runs well however occasionally it coughs, feels like it is dragging something heavy, belts out white/grey smoke then continues as nothings happened. this happens if i stay in one gear for too long when accelerating or if i hit about 65mph on a motorway or if i cruise down hill then step on the gas. Oil is un contaminated fuel filter is new coolant stays at same level. I tried a stop smoke type product which seemed to help but it still does it & has now failed the emission test. Any ideas?

Thanks Ian

Answer
Ian,

Sounds like an oil control problem at first look.  I would perform a compression check to see what the cylinder pressures are.  Write them all down and then squirt about a teaspoon of oil in the cylinder and perform the test again.  If the pressure goes up by 10 pounds or more you have defective and worn rings.  If not you might have plugged return holes in the head for oil return and the oil is getting sucked into the cylinder via the valve guides.  Now, the cough part seems to mean that the fuel pressure regulator might be a problem and needs to be looked at.  Have the fuel pressure checked at idle and at off idle to see if it is within norms.  If the fuel pressure is too much you get too much fuel and that will cause the rings not to hold since the oil is getting washed out by the excess fuel charge.  If it is this the correction, a new fuel pressure regulator could solve both the cough and the smoke.  Email me back and let me know what you find.