Engine/Transmission (1994 - 1998) Blue smoke

[DavidGardner]

Friends truck 96 2wd auto. Stock except for TST 230-605 fuel plate. Problem-truck drives down road ok. until step on throttle and then excellerates to about 2300 rpm and then starts vibration and blue smoke out the back. Seems like it is loosing power until he lets off the throttle and then its ok. I tried it and with the trk sitting still in park push throttle to 2400 rpm and some blue smoke but not real bad. Drove trk and checked in 2 on gear and floor it black smoke (normal with tst plate) and no blue smoke runs fine all the way up to 2750 rpm where it starts to defuel. This is normal I think. Engine feels very strong but problem happens in 3rd locked up and 4th od locked up. I am leaning to a transmission problem but dont know where the blue smoke is comming from. I always thought blure smoke ment oil in combustion chamber.



Any ideas or suggestions? Thanks in advance.



Dave Gardner

 

[Blakers]

Does it smoke blue only when it's cold, or when it's warmed up too?

 

[illflem]

Blue smoke usually indicate it's burning oil. Sure he's got just diesel fuel in his tank?

 

[drees1]

Blue smoke can be unburned (liquid or vapor) diesel fuel in a warm engine. Maybe a bad injector or one that is sticking or not atomizing the spray properly. Many people associate only black smoke with unburned fuel, but it is really burned fuel, just not completely burned, rather reduced to soot and carbon. Diesels that burn blue when warm usually have a pretty good eye watering raw fuel smell. Drive behind it and see.

 

[DavidGardner]

Blakers

It smokes the blue smoke after being warmed up. Is there anyway the oil from the transmission could be getting into the engine?

I still think he has a transmission problem. I am just puzzeld by the blue smoke. Iknow that some times if the engine is cold it emits

white smoke, I also know that some times under load or heavy acceleration it will emit black smoke (especialy if it has a fuel plate and the star wheel has been turned foward) what has me puzzeld is the blue smoke only in 3rd gear or 4th gear lock up under hard acceleration. Also it seems there is a power loss when this happens. It just wants to lay down and quit until the accellerator is let off. Then everything works ok. until the next time he gets on it as in a passing situation.



When this gets fixed or resolved I will post what the problem is.

With only 85,000 miles on his trk I can"t belive he has a broken ring or worn out engine.

 

[Champane Flight]

Temp

All diesels run better when compleatly warm or hot. I left a trail of blue smoke on the way home from work yesterday. There was a chill factor of -25 and I didn't have my truck plugged in. I didn't take the time to warm it throughly and took off with a light pedal. I have seen it for years and is just the sign of a cold engine, and cold fuel in most cases. Take this same truck out, run it, pull with it, and get it hot. Most likely the blue smoke will cease. This also happens a lot if an engine is not worked often enough, carbon builds up on and in injectors. It is a sign of unburnt fuel, maybe a partialy clogged injector, bad fuel, or just not warm. Put a little fuel treatment in her and go pull a house, chances are, it will clear up.

 

[Blakers]

Originally posted by David Gardner

Is there anyway the oil from the transmission could be getting into the engine?

I don't believe there is any way it could get into the engine from the transmission. There is no vacuum line to the manifold or anything like that like the older gas engine trucks had.



I know what you mean and why you ask the question as we had a 74 jimmy truck do that - sucked all the oil out of the transmission and burned it - much of it actually went by the rings and filled the crankcase.



But again, there is no way the transmission oil could be sucked into a Cummins engine.

 

[drees1]

First, if there is any loss of transmission oil or cross contamination, you would notice a drop in trans level and an increase on the engine oil level. But I don't think cross contamination is possible on your truck.



Second, Diesels rarely have a serious problem that does not get worse fast. In other words, your engine is fine, it just has a minor operational problem. Forget about it burning engine oil. If it was doing that to the extent of being blue smoke you would be adding oil at a rate of a quart in a few hundred miles. Also, the exhaust would be wet with oil slobber. I have seen plenty of semi truck engines with broken rings and pistons and they use 2-3 gallons of oil a day and still do not smoke blue. They slobber out the exhaust with a black oily residue. If they do smoke, they are burning off accumulated oil in the muffler from a long idle period before going to load, and they don't miss or sputter.



The fact that you have a power loss and a vibration is where you need to start. You have a miss or dead hole or bad injector. Pull the injectors and examine the tips carefully. One may appear wetter. If you can borescope the cylinders with the injectors out look for a bad spray pattern on the top of the piston. Air in the fuel can cause similar problems, low power, uneven running, and smoke, either white or blue. Any fuel smell under the hood?



I would place my money on a bad injector or air in the fuel. Also, low fuel pressure could contribute, but I am not so sure on our engines. fuel filter and strainer nice an clean??



Have a diesel technician drive with you and make it do it, he will probably have more ideas. Let us know what you find, and if there is any other information as to condition or symptoms post it. Good Luck!



Doug Rees

 

[DavidGardner]

Thanks for all of the replys. We drove the trk again today and put about 40 miles on it. No problems other than I feel that the transmission is slipping in the 1 thru 3 gears until it locks up in od. which happens at about 35 to 40 mph. No blue smoke today. The engine seems to run fine. I must add that about 2 weeks ago we did switch out the fuel sender unit on the fuel tank and did have some problems with reconecting the fuel lines to the tank. We are thinking maybe we are getting air in the lines and this may be causing the low power-missing situation. We will be checking the connections again to make sure there is no air being drawn in to the fuel line.



I will let you know what we find. In the mean time keep on giving your opinions and tips. They are very usefull and appreciated.



Thanks again Dave Gardner.

 

[DavidGardner]

Found problem

Found the problem for the low power (intermitant). He had an aftermarket Racor fuel filter mounted between the lift pump and the regular fuel filter. After talking to a few guys I told him to check this filter. He replaced it and took the old one apart. Found out it was full of black looking goo. Truck runs just fine now and no more problems with intermitant power loss. I still feel he needs to update his stock auto transmission. Again thanks for all the help. Once again this site has proven to be price less.