White smoke on decel
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Senior User
Joined: Nov 2008
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From: Sorrento BC, Canada
White smoke on decel
I just noticed that when I let off the throttle on my 91 7.3, that it blows white smoke out the exh pipe at rpms over 2000 rpms. I am running wmo, and it runs good on it. The smoke quits after about 5 seconds of decel. What could the problem be? Thanks.
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Senior User
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From: Sorrento BC, Canada
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Post Fiend
Joined: Nov 2003
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From: Nutter Fort, WV
Do you have a pyrometer installed?
Given how much thicker WMO is than diesel and how many more BTU's it contains I have to wonder if you may be having head gasket problems.
Given how much thicker WMO is than diesel and how many more BTU's it contains I have to wonder if you may be having head gasket problems.
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Thread Starter
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Senior User
Joined: Nov 2008
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From: Sorrento BC, Canada
I do not have a pyro installed, and I have done recent head rebuilds due to exh chuff, so the head gaskets are fresh. I also use my mirror to watch the exh pipe to tell me how much throttle I can apply until the black smoke point is reached, then I back it off until the exh is clear. The exh at idle smells of burnt wmo not sweet. I had thought of burning coolant too but the rad doesent bubble, and I havent lost any coolant. 6 of the injectors are original and have run 303,000 kms but I have had too many other projects in the way on the truck to replace them. Thanks.
Lead Driver
Joined: Nov 2003
Posts: 6,900
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From: Campbell River, B.C.
I wonder if the EGTs drop too low to burn the fuel completly when you are coasting or engine braking. Diesel burns much easier than WMO.
Maybe the thick oil is causeing timing to get thrown off. Are you running a fuel preheater?
Maybe the thick oil is causeing timing to get thrown off. Are you running a fuel preheater?
Posting Guru
Joined: Jan 2005
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From: Douglas, Georgia
so, have you made sure the fuel line is clear and filter is good?
This was a regular issue when running thicker fuels that were near the gel temp in the winter. If the filter plugged, and I let off the accellerator i'd leave a huge white trail of smoke.
This was a regular issue when running thicker fuels that were near the gel temp in the winter. If the filter plugged, and I let off the accellerator i'd leave a huge white trail of smoke.
Lead Driver
Joined: Nov 2003
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From: Campbell River, B.C.
Running motor oil is also really hard on the lift pump unless you are thinning it out with diesel or heat first. I remember trying to pump waste engine oil with a few electric fuel pumps I had lying around (on was originally from a diesel), and all of them could only manage a trickle and would quickly overheat. The pumps in these trucks are driven off the camshaft, so theres no motor to overheat, but you are still pushing the limits of the pump.
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Senior User
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From: Sorrento BC, Canada
Would a heat exchanger hooked up to coolant lines before the lift pump help? I tried using my stock trans cooler to heat the oil, but the first hill i went up the engine stalled from MAJOR lack of fuel. Also I just pulled my glow plugs to look at them and they were coked enough to put a resistance on getting them out. Thanks.
Lead Driver
Joined: Nov 2003
Posts: 6,900
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From: Campbell River, B.C.
The cooler in the rad is not going to add any significant heat.
To run motor oil by the book, you start on diesel, and shut down on it so that the engine is always at operating temperature when ever running the oil.
Then you have a coolant heat exchanger on your heater hose to preheat the fuel oil before it reaches the lift pump. HOWEVER, many guys opt to send coolant lines strait into the fuel oil tank to heat it right at the source and eliminate the viscosity problem throughout the fuel system.
Personally, I've only burned blended fuel and not strait oil (1/5 ratio at the most). Engine seemed to like it, but cold starting was more difficult in cooler weather (close to 32F) if I forgot to switch tanks before shut down.
Also understand that none of this is really recommended and if something breaks, consider yourself warned now. You are taking a risk here. Many are running it, but this is by no means an exact science.
To run motor oil by the book, you start on diesel, and shut down on it so that the engine is always at operating temperature when ever running the oil.
Then you have a coolant heat exchanger on your heater hose to preheat the fuel oil before it reaches the lift pump. HOWEVER, many guys opt to send coolant lines strait into the fuel oil tank to heat it right at the source and eliminate the viscosity problem throughout the fuel system.
Personally, I've only burned blended fuel and not strait oil (1/5 ratio at the most). Engine seemed to like it, but cold starting was more difficult in cooler weather (close to 32F) if I forgot to switch tanks before shut down.
Also understand that none of this is really recommended and if something breaks, consider yourself warned now. You are taking a risk here. Many are running it, but this is by no means an exact science.