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Topic: Exhaust smoke (Read 860 times) previous topic - next topic

Exhaust smoke

Heavy white smoke at exhaust during start up and idles rough. When warm all is ok and runs normal  U295, '99, 350hp

Re: Exhaust smoke

Reply #1 –
Many varables can cause white smoke during a start up, things that add to the possibility of white smoke is low compression, water in fuel, cold temperature valve adjustment, injector condition, quality of fuel for example.

White smoke is unburnt fuel, so that is a clue to what is going on.

I am certain you will get many ideas to the white  smoke..

If it is more than a puff of white smoke, a deeper investigation is in order.

Good luck

Re: Exhaust smoke

Reply #2 –


Are we talking cold weather or now? High altitude visit? Rough idle usually indicates one cylinder not firing. How long does smoke/rough idle last? Does it suddenly smooth out after 20 seconds with smoke then gone? How about restarts later in the day or is problem limited to morning starts? Mine does that in winter a bit for 5 to 30 seconds, depending on temperature, worse at high altitude.

Try mixing a hair of bat and eye of newt.

OK, go to truck stop, car part store and buy some injector cleaner and use that for a tank. Suspect it may be an injector leaking down after shutdown or poor spray pattern.

The offending injector/cylinder is easy to find. Start up in the morning, let it run rough until it just starts to run on all cylinders. Turn off quickly and go to engine compartment. Feel exhaust manifold at each cylinder until you find one cooler than the rest. This is the bad cylinder/injector. Use pyrometer gun if you don't want to touch the engine. Has worked for me on several engines.

Could be other stuff like Dave mentions but the injector cleaner is cheap and easy and the first thing to try. Then cross your fingers.
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Exhaust smoke

Reply #3 –
Sounds like air in fuel system, hose, filter, etc. jc
JC
1999 U320

Re: Exhaust smoke

Reply #4 –
Yep, could be air from leak down or like you say, hose, filter. I have used the chassis mounted hand pump to purge the lines, filters. I put a gauge on top of the primary filter. I pump until the gauge indicates 9 to 12 psi and then keep pumping for a minute or so. Gets rid of most air in the system and can be used to check for any change in start up symptoms. Also good for getting the last bit of air out when changing the big fuel filters just before tightening.

My rubber O rings in the hand pump were bad but just took old to NAPA store, compared to their O ring tray and changed for 20 cents. Only takes a minute and a small crescent to check on the condition if uncertain.
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Exhaust smoke

Reply #5 –
Ok, as long as we are guessing, why not get into the question: oil in radiator, water in oil.

Oh we could go crazy in the guessing games  :o

Re: Exhaust smoke

Reply #6 –
Dave, this is no guess on my part, our 97 270 with the C8.3 had the white smoke problem, it lasted longer than a puff or two so I knew had one of two problems, a leaking injector or a blown head gasket, it turned out to be a bad injector, if it had been a blown head gasket it could have turned out to be a real pain if it had created a hydrostatic lock, the damage could be bent rod ,cracked head, or broken piston.
The selected media item is not currently available.Bill&Doris 97 U270 36'
University of Parris Island Class of 66
Semper Fi  Build# 5174 MC#17094

Re: Exhaust smoke

Reply #7 –
Bill, Fully agree, one never knows until one gets into the problem. Guessing is just that. Have fun.
Cheers