I have a 1992 Ford LTL with a Mechanical N14 STC. Has 184,000 original miles. When coasting down a hill with no throttle I can see an occasional puff of smoke out the stack....lasts a couple seconds and goes away. It doesn't do it all the time....just happens every once in a while. Anyone have any ideas what may be causing this? Thanks in advance!
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Mechanical Cummins N14 STC Smoke Question
- Thread starter Akmc5
- Start date
Wes J
Senior Member
Your STC valve may be goofing up once in a while. I don't think I'd worry much. Sounds like yours is working better than most. 
Truck Shop
Senior Member
Check the fuel line that runs from the STC control to fuel system and see if there is engine oil in that line, it should be only clean fuel in that hose. If there is the STC control
is bad and needs replacement. The STC system operates off engine oil pressure to advance and retard injector timing, internal oil leakage to fuel side of the STC was and is
a common problem. Next it probably needs a tune-up on the valve and injector settings or adjusting the overheads. If you do that adjust according to the procedure in the
link I posted below, you will find it will run much better and you will extend the injector life.
http://www.chathamfuel.com/generic....Tech Tips - NT/N14 OBC Overhead Set Procedure
Truck Shop
is bad and needs replacement. The STC system operates off engine oil pressure to advance and retard injector timing, internal oil leakage to fuel side of the STC was and is
a common problem. Next it probably needs a tune-up on the valve and injector settings or adjusting the overheads. If you do that adjust according to the procedure in the
link I posted below, you will find it will run much better and you will extend the injector life.
http://www.chathamfuel.com/generic....Tech Tips - NT/N14 OBC Overhead Set Procedure
Truck Shop
Queenslander
Senior Member
We had an M11 that would blow smoke intermittently, only when lightly loaded.
Drove us crazy.
Eventually traced it to a gauze pad that covers the breather tube inside the valve cover.
The engine appeared to have a normal amount of blowby, and the tube accepted air when blown backwoods, but the penny dropped after we discovered pressure at the oil filler cap when it was removed at idle.
Gave everything a good wash and an overhead set while we were there and it has been fine since.
Drove us crazy.
Eventually traced it to a gauze pad that covers the breather tube inside the valve cover.
The engine appeared to have a normal amount of blowby, and the tube accepted air when blown backwoods, but the penny dropped after we discovered pressure at the oil filler cap when it was removed at idle.
Gave everything a good wash and an overhead set while we were there and it has been fine since.
Truck Shop
Senior Member
thepumpguysc
Senior Member
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"IF" the weather is decent TS.. go for it..
We all know your not doin anything, anyway.. Lol
We all know your not doin anything, anyway.. Lol