6CTA/450C black smoke and stall on start-up

Yesterday our starboard engine stalled immediately after starting, a couple times. Big cloud of black smoke. Third time, started as normal, ran as normal, no other symptoms...

The "pre-heater" thread got me wondering. Prior to this event, I've been trying to diagnose a fuel gauge issue related to that tank/engine. Turning the key on to energize the gauge, leaving the key on (along with the buzzzzzzz) to watch the gauge reading, key off, back on... several times until the gauge seems to display a believable reading... Did this three times over three days, but without actually starting the engine any of those times. And the pre-heater was going on and off during each of those...

The last of those tests was earlier yesterday, an hour or so prior to the event, and it took several tries and longer elapsed time before the gauge settled down.

So my question is about whether my yutzing around with the fuel gauge diagnostics was also causing the situation with initial black smoke and stalling?

Yesterday's start-up was just prior to a "barnacle run" up and down the river, and that engine acted completely normal throughout, raw water flow OK, oil OK, temps as expected, etc.

???

-Chris

What's you idle rpm? If set too low, when starting, rack will swing between start mode (full fuel) an zero fuel and puff out a big mouthful of smoke. This tends to happen if idle is set below 600rpm, but seen some do it when set up higher. I also find that as engine ages the idle speed tends to drift around, generally lower.

Tweak the idle up a touch, or if you have dual lever controls, advance throttle a touch on the start.

Worse when cold.

Doubt it has anything to do with flaky grid heater. Those don't do much for the actual start, but help some with the warmup blue smoke. Grid heaters like to burn up relays and are very hard on alternators. Not a fan of those.

In a mechanical engine I don't see how fuel could flow without the engine cranking.

Ski in NC said:

What's you idle rpm? If set too low, when starting, rack will swing between start mode (full fuel) an zero fuel and puff out a big mouthful of smoke. This tends to happen if idle is set below 600rpm, but seen some do it when set up higher. I also find that as engine ages the idle speed tends to drift around, generally lower.

Tweak the idle up a touch, or if you have dual lever controls, advance throttle a touch on the start.

Click to expand...

Ah. Thanks, that's reassuring. Our idle starts at about 540 and wanders up toward 580-590... only eventually getting to 600... I'll sort that!

Didn't do it when I just started that engine a few minutes ago, just after an oil change...

-Chris