Engine quit; appears to be related to fuel

[Browntrout]

We have an Islander 28 and sail in the Bay Area. This means that we deal with some heavy currents and winds, maybe every time out for some amount of time. We have had the boat about two months, and thus far the engine has been great. It has under 1000 hours on it and was well maintained. Two weeks ago we were coming into a marina and the engine quit abruptly. No spluttering; it acted liked an electrical problem. Long story short, after about ten minutes, I put about a gallon of gas in the tank and it fired up with perfection. An ambiguity is the gas gauge was right at half full. We can't tell if the tank drained and ran out of gas with a faulty fuel gauge, or if (somewhat famously) the fuel line has tiny perforations. So, tomorrow, I want to remove the fuel line that is prone to this and either replace or at least inspect. Question is where and how? Is it from the tank out? We have a Sierra filter just below the top of the tank, which then runs down to the fuel pump, which I believe is the original mechanical pump. How to check for the fuel line perforation issue?

[msmith10]

I wouldn't replace the fuel line without further diagnostics. It won't hurt to replace the line, but it may not fix your problem.
You described your shutdown as like electrical but are working on a fuel problem. Why did you jump onto the fuel line as the problem?
The fact that it restarted after putting in some gas may have been related to a cool down of electrical components.
Why do you think your fuel gauge was wrong?

[Browntrout]

Here is why we think it is the fuel line: because we have no electric issues and by keeping the fuel up almost to full, it hasn't happened again. Hardly a foolproof method. We are only going on what we know, which is almost nothing. But I have scoured the internet and this site and there is frequent mention of an abrupt shutdown caused by perforations in the line--once the fuel passes below the damage point, the engine fuel-starves. However, in that instance, it seems the engine would splutter and limp along for a bit (this is based on running a Willys jeep or a VW bug out of gas many years ago). Therefore, I can't defend my position, but it is the first thing that is coming to mind on what might have happened.

[Al Schober]

Your sudden shutdown has all the signs of a classic failure of the spark coil. Engine dies abruptly, after a cool down of the coil it restarts. Recommend you get two new coils. Install one, keep the other as a spare.

[Browntrout]

Thank you for that response with the coil. Is there a way to test that? Our issue is this has only happened one time. As an after thought, after you posted your remarks yesterday, we took apart the port hatch on top of the gas tank to try to get a visual on the fuel intake line--the hatch that includes the attachments for the fuel tank gauge. The tank was totally full. This adds a dimension of difficulty: my first instinct was the boat ran out of gas and the fuel gauge didn't work. I put about 6 gallons of gas into the 20 gallon tank, so therefore, no out of gas issue and more important, no vapor locking that we can tell. It APPEARED that one cause might be the tank vapor locking at the fill, but by removing the port, the tank was not vapor locked but was actually dead full. Sorry for the wordy response.

[TimBSmith]

Bracketing for fuel and spark diagnosis..

I posted elsewhere today and will repeat what I have learned and relearned here as a A4 owner with a couple of years here now.

My last sudden stop issue was a loose fuel filter that created just enough vacuum leak to prevent fuel pump from functioning.

I did not know if it was fuel or spark, or what part of these systems was causing the trouble.

I started with fuel, bracketing each segment upstream and downstream.

-Starter fluid caused combustion after engine stop. Throttle and choke did not.

No running the engine if any fuel smell detected or evidence of fuel leak detected.

1) Fuel level check with marked measuring stick.
2) Tank vent check.
3) Fill cap on and fill cap off run test.
4) Trace fuel lines for any signs of leak anywhere.
5) Trace all fuel pump connections. Including fuel pressure gauge connection.
6) Confirm airflow to fuel tank with air pressure.
7) Confirm fuel flow to filter with suction pressure. (This test failed. Found loose filter, tightened, that fixed trouble. My next steps would have been.)
8) Confirm fuel flow to pump fuel pressure gauge invaluable. Evaluate low or no pressure with secondary tests.
9) Confirm carb fuel flow.
10) Confirm carb function.
11) Use secondary fuel source to rule out dirty fuel and evaluate undetected tank leak. Pump out and filter tank to evaluate fuel quality. Use test strips to test fuel quality.
12) Test any hypothesis about fuel level covering pinhole by pumping out tank testing fill level, and using more advance testing with diagnostic smoke etc.

That's far enough on fuel for now. Others more experienced please augment as desired. This is my fuel approach with my current level of knowledge and experience. The spark approach beyond scope here. Hope this helps. Here to support.