Here's the dilemma, 1986 F-250 (tow rig) with an IDI 6.9L diesel. The thing smokes like a freight train and is just plain hard to start. I just put on a known good injector pump, and it still smokes. It's not a white or a blue smoke...just a plain black smoke from idle to WFO that leads me to belive overfueling. (I was raised on gassers, so I don't know what exactly causes what type of smoke on diesels) I've tried playing around with timing but I can't get the injector pump to move. (turn) Yes I did loosen the nuts. :flipoff2:
What should I look for?

Edit: Low on power also...Could that be retarded or overly advanced timing? Remember, it's a THICK cloud of smoke coming out of the tailpipe.

might want to post at www.thedieselstop.com as well

might want to post at www.thedieselstop.com as well
'preciate it....but that's the first place I posted. :smokin:

Have you checked the intake for restriction like a dirty filter or something.

Well lets see.......

Dirty air filter will sure make it smoke like a train
turned up Fuel pump will also
and Higher HP injectors


Mine smokes like a train...but only when I want it to:D

yeah with black i wouldthink fuel too. but what kind of shape are the glow plugs and thier controller in?

Good glows....good controller...and it's a greyish smoke, not a black like I thought. Injection pump is known to be good and all 8 injectors are remans. The smoke is BAD at idle and gets worse with higher RPMs. I wouldn't mind the smoke, if it came out ony when I wanted it to...but damn this is rediculous.

Edit, almost forgot, just as bad without an air filter.

I dunno...logic sez that something must NOT be as you think/say.

IF the pump, injectors, and airpath, ARE all good, then it would NOT be smoking black. So one of 'em MUST be bad. QED. :D

Diesels are easy: if ya got air, fuel, and compression...they run.

It really sounds like an air-restriction. Don't just take out the air filter...climb on up there and shine a light down the throat...see if something's blocking it.

Does it crank easily and take a long crank to start?

If so, maybe the engine's shot...bad compression. That -might- make it smoke all the way from idle on up....but it's a stretch. And even so, it oughta go away when warmed up.

Glow plugs don't have anything to do with it. They're only on for 7-8 seconds.

Air....I keep coming back to air...

oh...hmmm....check your exhaust too. Diesel mufflers can get pretty badly clogged with carbon...the backpressure can impede intake flow...although the 6.9 has hardly any overlap as I recall...hmm....

Timing...hmmm....bad timing doesn't usually cause -black- smoke...but I suppose....if it was REALLY retarded....it might. But at idle too ?? That's pretty unusual.

Please be sure to post back here and let us know what it was, for future ref...

If so, maybe the engine's shot...bad compression. That -might- make it smoke all the way from idle on up....but it's a stretch. And even so, it oughta go away when warmed up.


wouldn't low compression cause incomplete combustion as well causing the black smoke/

but wtf do i know... just a jeep guy roaming the forums. :D

Grey Smoke...... would make me think timing and then i would question over fueling. I would suggest checking your timing. Check where the adjustment is turned to on your fueling lean it out a little, it sounds like it is metering too much fuel at the wrong time in the firing sequence, still makes me think its a combination with the timing being off.

the suggestion of compression isnt a bad one, wonder if you are sucking past a valve or two. How many miles on this motor what is the sevice history.

Glow plugs are not relavent once she is running.

Yah, I wondered about the pump-setting too, but he said he put another "known good" pump on, and it'd be weird for two diff. pumps to be turned too far up so badly.

So maybe it IS timing. But it seems like even if the original pump was mounted wrong, he would've gotten the 2nd pump in right. Unless he visually copied the 1st one's (wrong) timing exactly instead of installing #2 by the procedure... :D

Go to the dieselstop 6.9 forum and search the archives. There's an excellent writeup on timing these pumps.

ps; gumbo; yeah, low-comp might cause incomplete combustion, which might leave carbon comin' out....i.e. gray/black smoke. It was just a guess....I've never seen one smoke black from that cause.