Ok....I've got a 95 F350 with the 7.3 Powerstroke. And like a week ago it started sounding funny, like it was lacking fuel, but yet it was smoking like a chain smoker with grayish/white smoke. So I checked fuel pressure and it was quite low, so I checked my fuel filter and it was a little gray, but not bad. So today 2-1-10 I replaced the lift pump. Now it runs like a rapped ape, but it pours out grayish black smoke and has a fuel knock that's killer! I'm guessing there's still a bit of air in the lines which is causing the fuel knock. I've checked the turbo for spin and vane conditon and they are good, I've checked the HPOP and its good. I'm wondering if my MAP sensor could be shot? Or what the problem could be, and I would rather not spend the $75 an hour for someone to play with it for a while, cause well....I can do that. But it just seems like it gets worse by the day

 

Well, not to be a smartass or anything, but this is why one spends $75/hr for a mechanic that knows what to do. Presumably, the mechanic will know what's wrong and fix it.

 

Lol, you would hope so. I work on mostly Cummins and Detroit engines, and so far this little powerstroke has me dumbfounded. Me and the guys at work have all discussed what could be wrong, and none of us can figure it out.

 

I never take it to the shop just cuz when they do it they're usually wrong. so i just eventually do it myself. sounds like some air in the system. just bleed your injectors, might take a couple times of doing that.

 

Sound's like it may be a cracked injector tip.

 

White smoke is raw fuel, black smoke is fuel with insufficient oxygen to support combustion.
Is the smoke a constant haze or does it puff?
How is your blow by? Pull the oil fill cap.

Do you have access to a scanner that will pull codes, buzz injectors, ect? If so, I would run a Cylinder Contribution test, Buzz test (IDM codes will be displayed only after a buzz test), and if you can't shut down injectors you will need to pull the valve covers and disconnect individual injectors to isolate your problem cylinder(s).

 

Well....took it to ford. They scanned it and ran a bunch of tests then told me their best GUESS is that the timming chain is stretched. I could guess all day, but it may or not fix it. The truck does have 412000 miles, so ill spend the 50 and put a chain on it. It can't hurt