Really really frustrated...

[Guest]

I've had recurrent issues with my late model (1978!) A4 stumbling, then shutting down inexplicably after running well for an hour or so. My boat doesn't get a lot of use so I've addressed this issue in bits and pieces over the last couple of seasons. Every time I think I've cured the problem, I'm dissapointed again.

The engine has been well maintained, always properly winterized. I use fresh 93 octane fuel with recommended amounts of MMO and stabilizer. Gas fresh this year. I've replaced everything from gas tank to carburetor (inclusive). I have both a water separator main filter and a polishing filter, all parts purchased from MoyerMarine with exception of gas tank that was custom fabricated last year.

Motor ran well this spring until it began to misfire and stumble after running about an hour at cruising speed in calm seas. The motor then stalled. I drifted / sailed back to home and I tied up. I really thought I finally figured it out when someone on this board suggested a blocked fuel vent hose to another post. That *had* to be it!! Got back to the boat yesterday and checked - nope - vent clear.

The motor started yesterday but initially was very choke sensitive - needed to choke to start, wouldn't idle without choke and would abruptly stall when I increased throttle. Spark plug electrodes are white / clean and free of any soot or carbon. Motor eventually smoothed out and appeared to run fine under load at dock. Have not yet tested out in open water again.

All of the above really makes me think fuel issue but I've literally replaced the entire fuel system. The carburetor is about 4 years old now.

Ignition system is Indigo electronic and has to my knowledge been trouble free.

Any thoughts? Please?

Thank you!!

[ndutton]

About an hour, huh? Electronic ignition, even if it is the Indigo optical trigger type. Will it restart after a half hour?

Dare I say it? Oh, I dare - I dare.

After you've thoroughly exhausted your fuel system diagnosis have a look at your coil. More accurately, examine the ignition system. Measure the coil input voltage at cruising RPM, measure the coil primary resistance at rest and if possible immediately after shutdown. Check for strong, snapping spark while cranking from the coil secondary lead to the block immediately after shutdown too. Be sure to close the intake thru-hull for the spark test.

Please report back with the results of these few tests.

[Dave Neptune]

Be sure???

All that's left is FUEL PREASSURE at the carb, do ou know that it is preasurizing? The "whitish" plugs are indicative on a lean condition which would cause your symptoms This typ of diagnosing is why I always recomend a cheap fuel preassure gage, it elemlnates a great deal of GUESSWORK.
If it is preasurizing Neil is probably on the right track.

Dave Neptune

[Sony2000]

That last run was too lean and stripped the plugs of carbon. The small idle jets may be blocked.

[sastanley]

I have one quick suggestion since I agree with Neil about the coil based on your report, if in fact the fuel system is as you say.. I did the same thing..all the way thru the fuel system including the tank....45-60 minutes it ran like a top, and sputtered to a stop.

Here's my tip...stop wasting money on high octane gas...the only difference is that it burns more slowly than lower octane gas, thus helping to retard detonation (pre-ignition) in high compression engines..In a 6.3:1 compression ratio engine like the Atomic4, it makes the fuel more difficult to ignite, especially if your ignition system is/may be compromised with a failing coil & weak spark.

I used to burn high-test fuel in all my small engines until someone explained the above to me..now it all makes sense and I save money...well except for both of my cars now require high octane gas...

[longhorizon]

Thank you Neil, Dave, and Shawn.

Well, here it is - another season. Last season came and then went in a flame out called Sandy. Boat survived just fine (but the house is a different story!).

Over at the boat yesterday - de-winterized. The A4 started up just fine and (again) runs like a top. Of course, I expect the aforementioned malfunction once I get to run her for a while. A couple of questions -

Re fuel pressure gauge - some difficulty anticipated. Current set up is a hard copper line from pump to carb (I think) with polishing filter set up pre-pump. Any recommendations on pressure gauge (Mnf, model)? Plumbing?

Re electronics - Tom Stevens was kind enough to send new innards for the distributor (in unlikely event that there's a heat-related problems there). I have a new coil (somewhere) that I will install. I do have passing familiarity with a multimeter but can someone please give me a step-by-step regarding connections and settings so I can run the suggested diagnostic tests?

Thank you so much. Will definitely report back to the group once I have some answers.

Thanks again.

Etoile Filante
T-34C #515

[ndutton]

What is to be the strategy, fuel or ignition first? I do not recommend chasing both at the same time. Whichever you choose let's see it to its conclusion before moving elsewhere.

[Mo]

Hi guys,

I'd be very suspicious of water in the fuel. Same thing happened to me 3 yrs ago...and nicely cleaned off plugs to go as well...water will do that too. I would try draining the separator and look for water. If you find it put and hose to the bottom of the tank and suck about a gallon out. Have the gallon empty into a clear container and look for separation...water will go to the bottom. Wait about 20 minutes or so and do it again if you suck water ...continue until clear gas.

Another option might be to connect an auxillary tank and run the engine from that...if no symptoms you know you are back to the fuel.\


EDIT: Just noticed the Dates: IF the boat is on the hard now would be a good time to draw some fuel from bottom of tank and see if there was water...it would have all settled.

[Sony2000]

If he suspects or finds water in the tank, he can add 4-5 ounces of gas line antifreeze to burn it off.

[longhorizon]

Will look again but one of the earlier times this happened I was concerned as well and checked the filter/separator - no water found. Still, worth checking again I believe.

I do believe other issues (either lack of fuel pressure) or ignition likelier culprits.

Thank you. If anyone can take me through a methodical multi-meter walk, that would be great. Thanks again.

KS

[Carl-T705]

SAStanley is correct about the octane issue. Although you can't convince many people of that. Many have an assumption that octane is power, it is not, the most combustable gas is low octane. Good post by MO on the water in the fuel cleaning the combustion chambers too. There is a wealth of knowledge here for sure!

[sastanley]

KS, Neil is right..pick one battle at a time...sorry about the house, glad the boat is OK. I had the same experience with Hurricane Irene a few years ago..boat unscathed...but had house damage and a crushed SUV at home..I only had 7 trees come down.

Hard copper lines...mechanical fuel pump?? I eliminated my hard lines and went to hose barbs and A-1 alcohol rated soft hose everywhere on my boat..no more hard copper getting in the way. Even though I eliminated the hard copper line, I still have and really like mech. fuel pump...I put a soft line and the Moyer 7micron polishing filter and a fuel pressure gauge in there instead.

[romantic comedy]

Kai,

When I had a similar problem, i t was an intermittent electric fuel pump.

I would suggest taking the fuel pump out of the equation, for testing.

You can use a gallon jug, placed on the nav station. Just run a fuel line to the carb from the jug. Gravity feed. If you need more then a gallon, you can use a bigger tank or refill the jug. It goes down quick.

The higher octane fuel is made to burn more slowly, and is not necessary in the Atomic Four. 87 octane is fine.

[Skywalker]

Just a comment...

Facts, experiments, measured outcomes.

What's wrong with you guys? Don't you know we live in an age of belief and hocus pocus!

Geez, pretty soon you guys are going to suggest I buy a manual or something to read!

Carry on.

[Mo]

If he suspects or finds water in the tank, he can add 4-5 ounces of gas line antifreeze to burn it off.

They are using ethanol in the US and I don't think the gas-line antifreeze works as it used to with "normal gas". I carry gas line antifreeze on the boat but have to be careful not to get ethanol...we have some stations selling it here now.