Hi all,
I looking at a 1997 Ford F-250 7.3 powerstroke with around 107,000 miles. I
know very little about the powerstroke. when it first starts up the is blue smoke and calms down as the engine warms up. My question is this normal?
Bad indication? what tests can be run to determine if this is a serious problem or normal. i know powerstrokes have snooty exhaust. This just want to know i'm not buying a problem. Please let me know if you can help and/or if you need addition information.
Thanks a bunch,

Jim

 

If its white smoke then its raw unburnt diesel, which at cold startup is normal. If it truely does have a blue tint to it then its burnt oil. Its most likely bad injector o-rings, but could potentially be rings. The only way to check this out is through a compression check. If its rings then you're talking extensive bottom end work. If its o-rings then it will require removal of the injector which is a simple deal. To have a dealer do it will still be relatively spendy ($500+).

 

Is it just a puff of smoke or is it smoking heavily?

 

Thanks for the replys. It smokes very heavy blue smoke at first start and continured for a good 10 minutes (this is at idle) then calmed down some. Then went I drove it down the road I could still still see faint blue. I going to check out the truck today, really pay attention at startup and time how long it smokes blue, I'm taking to independent shop that has a great Ford mechanic and have him evaluate futher. But I really apppreciate the input. I just dont want to buy a can of worms. But if it was just "0" rings and it cures the blue smoke problem. You said white smoke is ok at start-up, unburnt diesel, when it is warmed up should the exhaust show clear? No blue or black? Only a black plume under hard acceleration? I just trying to figure out how the exhaust should look at startup and underway.

Best Regards,

Jim

 

Puff of white smoke at start up is normal, especially when cold.
Black smoke under heavy acceleration is normal.
Blue smoke is not normal.

 

No its not normal, not in stock form. Only in a very rare case should you even get a puff of black smoke when the engine is stock. Thats only when lugging the engine under load or at high altitude. If you are getting anything more than just a slight puff of haze when stock then you're either restricting airflow or your fuel pressure is hosed. If your air filter is plugged, your turbo fins worn down, CAC boots leaking, or the ebpv engaging then you're not moving the volume of air you need to burn all the fuel. If your fuel connections at and in the tank are sucking air (which they most likely are) then your fuel pressure is dropping. These engines like to run close to 75psi to the heads. The flow design of the heads is also horrible so you're not getting decent or even pressure to the injectors, well not without a dual return system. Your fuel filter could be causing it too if its plugged up. If you can't get enough pressure to them the fuel doesn't atomize well and you end up with large droplets. These in turn don't burn well at all causing black smoke. My truck in stock mode won't smoke at all. It'll only smoke when I'm in my higher chip settings, and even then on 80 its only because my fuel filter is plugged.

 

An idea:

If it's smoking at start up it may be because the engine is cold and the piston ring to cylinder wall tolerance is greater allowing oil to get in the cylinder. As the engine warms the tolerance gets less and helps seal enough to keep less oil from getting in the cylinder. It's just a thought....basically worn cylinder rings. Hmmm, but with only 107k miles??? ~ good luck in finding out the situation. Don't know about diesels, so I may be off track

Like we used to say on the drag strip....loose pistons win races!