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4108- One Cylinder Running Hotter

bigrocksailing

New member
Hello-

I`ve recently had a black/grey smoke issue and fuel out the exhaust in my 1984 Perkins 4108.

I discovered a kink in the Sbd fuel supply line and at the same time found a partial block in the port tank return line. As I run with all manifold valves open, fuel was being pulled only from port and returned only to starboard tank. The starboard tank was pressed full, presumably causing some back pressure, and spilling back into port through the common vent fitting. Once I`d resolved the feed and return line problems the smoke improved (though not 100%) and the unburned fuel on the water decreased to near nothing.

Question 1: Could a bit of back pressure along the return line cause uneven burning as more fuel is forced into the injectors?

As there was still more smoke than usual I pulled off the dock in order to get a good load on the engine and try to blow the carbon out of the cylinders.

My rpm would not go above 2200 and the heat rose to 194 F which is about 10 warmer than what we normally see. Checking the engine, I noticed smoke from the aft most injector (the last one before the return line heads back to the tank). Thinking the injector was poorly seated (I just had them serviced) I returned to the dock, removed the injector and put a new copper washer on it. Heading back out on the water, once the boat was loaded up again (still not pulling full rpm) there was more smoke at the injector but, looking more closely, it seemed to be diesel residue smoking and not coming directly from the injector.

I put my IR gun on it and found that the engine at the injector base was 225 F while the 3 others were 198 to 200 F. Back at the dock, thinking maybe a bad injector, I cracked the nut and the engine misfired. To be sure, I pulled that one out and put in a new injector from spares. After firing up again, the temps remained about the same until (still at the dock) I put it in gear and ran to about 1500 rpm and found that the base of the aft most injector was consistently about 10 F warmer than the others.

Question 2: Anybody ever heard of a single cylinder overheating and what might be the causes of this? Could an excess of fuel spilling in from the return line cause a problem with the rings (oil level remains constant) or bog up the exhaust valves? Not really sure where to go from here.

While investigating the smoke I did pull off the mixing elbow. There was some soot so I cleaned it. From what little I could see inside the exhaust manifold it didn't appear overly built up.


Sorry for the long post. Any help would be greatly appreciated as I'd love to get out cruising again!!!

Thank you!
 
Checked valve clearances. Some needed adjusting but produced no change.
Flushed fresh water side twice with rad. cleaner. No change.

Was replacing the coolant after flushing and putting in a Dexcool knockoff that was recommended by a mechanic several years ago. Googled it and there are mixed reviews of it (including a class action suit against GM, the maker). Could find few specifics though on using Dexcool in a Perkins. Does anybody have experience with this?
 
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