Ive got a problem that has gotten worse over the past couple days. Sometimes when starting off from a stop the truck will smoke like a full on puller untill the boost builds. It only happens when it feels like it. I am not getting down on it, ******* it, mashing the pedal or anything. Just a "normal take off". The truck does noticeably surge without me pressing the pedal harder when the black smoke is pouring out. I cant duplicate it even if i try to lug it, dog it, with no boost built. I belive its an AFC problem because the smoke clears right up when the boost starts building.
My banks plate is full forward, afc full forward. I have the starwheel adjusted for just a light/moderate haze.
This smoke cloud is quite impressive i must say! But i would surely have a ticket waiting for me of some sort if an officer should witness this cloud of pure blackness erupting from the tailpipe . Thats the whole problem, it sneaks up on me, and it is WAY MORE than normal take offs, even hard take offs are no match for the mystrey smoking. It happened to me twice today and i totaly erased the car behind me! Thanks for any input -Jake

 

One of the most common causes of black smoke is an air inlet restriction. This can be anything from a plugged air cleaner, an intake hose collapsing or anything else causing an air flow problem even plugged exhaust. Injector malfunction is also a common cause for black smoke as is incorrect engine timing.
And hate to say it but injection pump malfuntion.

 

First off, do you think it has anything to do with the plate being full forward as well as the AFC?

I dont think its airflow related only because it happens only at low boost situations ie. only on start off. (full stop, 2nd gear, easy pull off, nothing harsh at all). It has a clean BHAF on it as well. I am not doubting you at all only letting you know my guess.

Also, am i correct in thinking that the truck would not pull harder when it happens if airflow was a problem??

It seems like when i first put the AFC forward and didnt adjust the star wheel, the truck would pour out black smoke before boost came on, i then adjusted the star wheel untill it was only a haze. This is the same looking situation as before i adjusted the star wheel, except it happens very rarely on start offs. On normal take off at a normal or harsh pace, the smoke is only a medium haze if that.

Boost builds well all of the time, truck runs clean unless i rev over 2400rpms and then it turns to a light dark haze.

Exhuast is straight piped except for the cat., but i dont suspect the cat. because if it were the problem, i think it would happen on a normal bases.

When it happens the smoke is always very thick and very black. Its is an enormus cloud that can envelope a mid-size car. The burst is about 1 sec long (as soon as boost builds in second gear, which is very quick).

I am focusing on the afc as the problem but cant figure out what would cause the afc to act that why.
But i am no where close to being an expert so if it were something else it wouldnt suprize me.

 

With your plate full forward your governor arm could be missing the plate completely and with the soft spring in the AFC could be randomly letting the rack travel too far forward under no boost conditions. You could also have an injector hanging open.

Is there any difference in the idle before the times it smokes? Could it be an sticking Over Flow valve?

I would back-up the Banks plate 1/16" as that is the furthest forward I have been able to get a Banks plate to work properly. Then leave all else the same and see what happens.
Bruce

 

From what i remeber the idle has been normal before the smoke appears. It seems to idle pretty smooth all the time, except on cold starts it has a rough idle for about 3 sec.

I just streched my over flow valve spring a week or so ago to .500, it was around .400 before i streched it. I noticed more bottom end with a hair more acceleration smoke.

Ive been planning on sliding the plate back a little so i guess its time to go ahead and do it to see if it helps.

 

Ah-ha
High fuel pressure could also be causing the problem. Maybe you stretched the OF spring too far. I knew a guy who had black smoke, when we put a FP gauge to it it was pushing 55 psi at idle, about twice what's recommended. New OF valve fixed it right up.
The correct pressure after stretching the spring is hit or miss at best and rarely lasts long afterwards.

 

It could also be your afc arm is hanging up on your plate. Make sure they are straight. Hope you find the problem!

 

The hotter more humid air will cause more smoke than winter time air, but from what you say it is worse than that.

Wastegate sticking open maybe?

 

Na its not the WG cause it only happens rarely on take off, and after that boost builds very good and the smoke is purty clean.

Infidel, if the checkvalve is pushing to high of a pressure, is it going to damage anything before i get a new one? And who had the new one for $20??

Thanks for the great info guys, i guess its a combo of the gov. arm hanging up, and the tight overflow valve. Ill let yall know how it turns out. Thanks -Jake

 

her ya go.......

Precision Diesel Injection and Turbo Inc.
Marty Tompkins
888-734-7349
$25 + $7 shipping and handling.

 

Besides poor performance the only other problems I've heard of is split fuel filters. Not a real bad problem but certainly enough to leave you by the side of the road with a mess.

 

Hmmmmm, poor performance? I guess the pressure is not too overly high because this truck is still running super. Seems to have gotten faster over the past day or so? My imagination could be messing with me though.

I just want to get this thing fixed or at least know its going to be okay for my trip to Muncie this weekend.

Ive been trying to get buy a local diesel shop today but dont have the time, mabye tomm.

 

Many consider black smoke as poor performance, especially the smog police.

 

Yep, police would have something to say if they saw one of those clouds.... I can avoid it now, i just keep an eye on the pipe when taking off, i can tell when it starts pouring and the truck starts taking off like crazy, then i let off and its just like normal again.

One thought, if it was the overflow valve that is causing the billow of black smoke, wouldnt i be able to replicate it to some degree??? Ive tried many times to see if its just my AFC that needs adjusting but when ever i try the smoke is always acceptable. Its just on occasion that it decides to load up the cylinders with fuel and blow black smoke and take off a bit quicker than usual.

I also adjusted my plate back around 1/16. Will see what happens tomorrow.

 

Besides the spring wearing out in the OF valve I've seen others where the ball and seat have become worn or scored. It could be the ball is occasionally hanging up in the seat producing an unregulated full pressure situation.