Black Smoke Solved by Changing Fuel Filter?

[Marshall Mahoney]

I have been fighting black smoke on one of my 6BTA's for months. I cleaned the air filter, after cooler, checked timing, and serviced the injectors. It was getting increasingly worse, and I was thinking turbo or fuel pump would be next on my list to check. I also noticed the the engine was not quite as responsive as the other, coming up on RPM's a bit more slowly. I also, rarly cruise above 2200 RPM.

I was running from hurricane Isaac, when RPM's dropped off to 2000 -- due to a plugged secondary fuel filter.

So -- I was running the boat back down river yesterday -- with no (significant) smoke! It seems counter intuitive that a fuel filter restriction would cause black smoke. I would think that it would cause the engine to run lean if anything. I don't want to claim victory until I can understand why. (Must be the engineer in me).

Do any of you have an explanation or similar experience?

[In Memory Walter K]

I've had black smoke when the hose (1 of 2) to the engine popped off. Check clamps.

[Bruce]

Poor fuel supply wont allow the engine to turn up thus not spinning the turbo and providing the proper boost for the fuel being delivered. I've run into that on a few times.

[Marshall Mahoney]

Thanks guys -- engine hoses are good-n-tight. Hope it was the fuel filters. Sometimes it's the simplest things (but I'm usually not that lucky...)
--Marshall

[Bruce]

Marshall,
Actually in over 40 years of working on internal combustion engines, 60% of the time its been simple issues.

Most repair techs I have met either have been trained or developed the wrong diagnostic procedures and look for complicated issues right off.

Eliminate the simple first. Its like a big block diagram layout with the simple at the top, not the bottom.

[Rocket]

My favourite diagnostic tool is to ask the operator in very fine detail what is the last thing that it or you were doing before you noticed the problem and then thinking "based on that information, what changed?" As Bruce says it is very often simple, eliminate the simple stuff first helps you figure out what it definately is NOT.

[Carl]

Dumped a ton of money into a machine that ran erratic...They swapped out boards, drives, motors were rebuilt and tuned, special grounds, new cables, rerouted cables etc. Company and their technicians tossed their hands in the air after multiple failed attempts...all of which I paid dearly for.

Talked with a guy on a forum I frequent about my situation. Turns out he used to work for that company, thought they made excellent machines and was never stumped by anything on them. At his request I scan and send him my schematics.
Next evening he calls with a plan, but first we are going to check power from building panel to transformer, from transformer to machine, machine to internal taps. I express how I think it is a waste of time, how we had electricians wire machine and technicians checked it...but he won't go further then starting at the beginning.

Fine...panel checked out, power to transformer checked out, power from the transformer is low, has me recheck and yep it's low...not real low, but low. So I change taps at transformer, then adjust at machine and the fricken thing runs like a dream...been 5 years since.

Keep it simple and start at the beginning.

[Charlie J]

ahh yes the old tap changer