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Old 23-05-2016, 19:12   #1
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How Do You "Fog" a Diesel Engine

I just finished rebuilding and re-machining the head of my yanmar 3GMD diesel. One of the problems the engine had was corrosion on the exhaust valves. I am thinking some of the corrosion (or maybe all) was caused when the engine sat for days or weeks with salt water in the water lock muffler and the exhaust system. Even if the water lock were drained, I would think the humidity in the exhaust would remain at near 100% for a long time. And that humidity could corrode the exhaust valves and maybe even cylinders or intake valves.

So is there a way to fog a diesel. I have fogged a gas engine, but that method would cause a diesel to fire. The yanmar manual does recommend disconnecting the exhaust hose for long term storage and taping over the intake and exhaust elbow.
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Old 23-05-2016, 19:35   #2
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Re: How Do You "Fog" a Diesel Engine

It just so happens I proof read a manual for a PERKINS licensee owners manual today... Removed the injectors put oil in the cylinders and turn over the engine. Put the injectors back in. It also mentioned removing the exhaust and taping it over. Good luck.
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Old 25-05-2016, 07:51   #3
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Re: How Do You "Fog" a Diesel Engine

tapped the waterlock (stainless) for a 3/4" hosebarb, little shut-off cock in the hose, connected to the diaphragm-bilgepump. If the engine was going to be stationary for more than a day I pumped it
(was possibly more 4 my peace of mind, as some water would always be left...)
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Old 25-05-2016, 18:08   #4
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Re: How Do You "Fog" a Diesel Engine

If it worries you, fit a plug in the top of your water lock so that you can drop a tiny amount of oil in there. The oil will spread and seal the surface of the water.

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Old 25-05-2016, 18:25   #5
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Re: How Do You "Fog" a Diesel Engine

Isn't diesel oil anyway? I can't imagine why you would need to do this.
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Old 25-05-2016, 23:23   #6
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Re: How Do You "Fog" a Diesel Engine

Use fogging oil as per a gas engine. It's the starvation of oxygen that causes the engine to stop full of nice oily mist that protects all the surfaces.
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Old 26-05-2016, 03:10   #7
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Re: How Do You "Fog" a Diesel Engine

You might even get enough diesel mist to coat the valves and prevent corrosion by lifting the valves with the valve lifters, setting full throttle and turning the engine over with the starter for half a minute, easy and worth a try.
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Old 26-05-2016, 04:38   #8
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Re: How Do You "Fog" a Diesel Engine

Good Thread. Thanks for the shared wisdoms.
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Old 26-05-2016, 05:26   #9
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Re: How Do You "Fog" a Diesel Engine

I tried once to fog my diesel, it started pretty quickly as I sprayed it.
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Old 26-05-2016, 05:29   #10
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Re: How Do You "Fog" a Diesel Engine

Shame the modern diesels dont have decompression levers anymore. Just crack them, crank it as you spray in the fog..

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Old 26-05-2016, 05:35   #11
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Re: How Do You "Fog" a Diesel Engine

Quote:
Originally Posted by NoTies View Post
Use fogging oil as per a gas engine. It's the starvation of oxygen that causes the engine to stop full of nice oily mist that protects all the surfaces.
This BUT you will have to stop the engine by stopping the air intake. Take off the air filter so you have a clean way to put a board over the intake. You don't want to try to use your hand or a rag. Bring the engine up to normal temp then with the board in one hand spray the fogging oil. The engine may accelerate so be ready to stop the intake air with the board immediately . It is a good idea to try killing the engine with the board before spraying the oil just to be sure your technique will work before introducing unmetered oil that the engine can use as fuel.

The safer way (but more work) is the remove the injectors and squirt oil in each cylinder . If you do that turn the engine by hand with the injectors out before reinstalling the injectors. When returning the engine to service be sure to pull the injectors again and spin the engine at least 2 full revolutions before attempting to start it. Hydraulic lock can spoil your day.
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Old 26-05-2016, 07:27   #12
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Re: How Do You "Fog" a Diesel Engine

Unless you can find a fogging oil that won't combust, you will have to find a way to lessen the compression.
I am sure there are synthetic oils that won't combust, but do provide good corrosion protection, but other than fire proof hydraulic oil, can't name any off hand.


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Old 26-05-2016, 08:05   #13
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Re: How Do You "Fog" a Diesel Engine

I get no air flow with the decompression levers on.
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Old 26-05-2016, 13:13   #14
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Re: How Do You "Fog" a Diesel Engine

If the engine is running on the fogging oil you're not spraying enough of it. The idea is to replace all the oxygen, without which combustion can't take place. Simply squirting oil down the injector holes will not protect valves and seats
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Old 26-05-2016, 13:20   #15
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Re: How Do You "Fog" a Diesel Engine

It's going to be tough to flood a Diesel, it would have a tendency to accelerate, maybe the old fashioned way of oil mixed with kerosene or Marvel Mystery oil, a bunch of it down the injector and turn over by hand?

I've done that with engines that have sat for years unused as I didn't want to start them dry.
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