Intermittent stall, Fuel issue?

[robshepherd]

Hello All,

While motoring to port in a flat calm yesterday afternoon, I mentioned to my wife that the motor was "purring like a kitten"... You already know where this is going, or I wouldn't be posting. It wasn't 15 seconds later (I'm not kidding!) that she started to stumble and cough. I finessed the throttle for a few more seconds, and then she died. Before I get to my question, I have some more info to share. This same thing happened last week on the way out of the harbor. We sheeted in and sailed off, and didn't try the motor until 5 days later upon entering the harbor again, at which time it started on the first crank (the norm). Both times that this has happened the motor has been at operating temp (about 165), and had been running for 30-45 minutes without issue. This made me suspicious of the coil, which I swapped for a spare, but the issue persists. She has a fresh tune up (points, plugs, rotor, condenser), AND I rebuilt both the carb and fuel pump last summer. Yesterday after cranking for about 5 seconds without firing, I pulled a plug and expected to see some gas. Plug was dry. Hmmm. Shouldn't there be some gas on it? My sediment bowl was full of clean fuel. I have a water separator filter, but no inline fuel filter before the sediment bowl.

The ONLY change I can think of is the addition of 5 gallons of 10% ethanol gas to my tank, previously holding about 5 gallons of ethanol-free. This was about a week before the first incident. Apparently ethanol-free fuel is no longer available in our area...

Do you all have some ideas to help me resolve the issue, and could the new fuel possibly be the culprit. I wouldn't think so, but not sure.

If more info would help diagnose, ask away please! Thank you for looking! Regards, Rob

[Dave Neptune]

Hmmm

Rob, I doubt it is the fuel itself unless it has sat for a long time! Did you confirm spark when attempting to start? Does sound like it's electrical except for the stumbling to a stop!

Clean fuel does not mean you could not have a filter plugging up or the screen in the sediment bowl. You could also be sucking a bit of air into the line and the fuel pump just can't keep up and finally not enough fuel. If you can check the fuel pressure and or good flow after confirming the spark we'll have more to go on. I assume that you have the mechanical pump so next time it starts to die before anything try the priming bail on the pump FIRST or even during a failing episode.

Dave Neptune

[JOHN COOKSON]

It's tempting to tie all this together and say the detergent action of the added ethanol broke something loose which is raising havoc in the tank and or carb.
I'll leave it up to you if you think this is worth pursuing.
The "acid test" for tank problems is to run off an auxiliary tank and note any change in performance.

TRUE GRIT

[robshepherd]

An electrical issue?

Dave and John, thank you!

Today I disconnected the fuel line between the (mechanical) pump and the carb, then operated the pump using the bail. PLENTY of fuel coming out with each stroke.

I talked to a gentleman in the harbor who has good experience with A4s, and he made an interesting observation. I'll describe, and see if anybody has other ideas.

We took a plug out of the hole, put the wire back on, and he had me crank the engine for approx. 3-second pulses. He noted that there was no spark DURING cranking, but the spark would appear as soon as I stopped cranking. He hypothesized that my battery bank obviously has enough amps to crank, but might not be delivering enough voltage to crank AND generate spark--And that my intermittent stall issue could be due to the alternator not working properly.

I suspect I can remove the alternator and have a shop bench test it. Might that be a good idea?

Thanks for looking! -Rob

[hanleyclifford]

Before pulling the alternator check voltage while running to see if the alternator is charging. With a voltmeter you can also observe voltage during cranking.

[ndutton]

Y'know what I think?

This thought is out there, WAY out there and either I'm going to be 'Da Man' or the village idiot. There's no middle ground.

I think there's a chance your points wiggled loose and are closed all the time.

I'll refrain from explaining why I think what I think because if I'm wrong - and there's a good chance I am - I'll look like an even bigger idiot.

[robshepherd]

Points looking good

Neil,

You and my friend at the harbor must think alike. Points is one of the first thing he wanted to check. My notes indicate a setting of .019, and a quick check confirmed that they were off a bit. As he put it "not enough to cause a problem, but let's set 'em correctly while we're here." There is also spark at the points while cranking.

Conversion to electronic ignition is on my "to do" list.

Thanks for the thought!! -Rob

[ndutton]

Glad it was checked, sorry it's not solved - yet. This is really sounding like one of our enigmatic multiple issues scenarios.

[hanleyclifford]

While .019" is indeed the theoretical optimum point setting, because of wear on the lobes on our old distributors it is often the case that .019" will not produce sufficient dwell to build the coil to sufficient strength to fire the plugs. Try reducing the gap to .013" and see what happens.

[ndutton]

Try reducing the gap to .013" and see what happens.

and keep a wary eye on coil temperature when you do.

Back to your buddy's theory of voltage drop to the coil during cranking, the coil only needs 9 volts to function. At that voltage you wouldn't be cranking at all so I'm discounting the idea.

[robshepherd]

While .019" is indeed the theoretical optimum point setting, because of wear on the lobes on our old distributors it is often the case that .019" will not produce sufficient dwell to build the coil to sufficient strength to fire the plugs. Try reducing the gap to .013" and see what happens.

Wow! That's interesting to be sure, and makes sense. I will give it a shot. Thanks so much.

Neil's comment about coil temp leads me to believe that reducing the gap may make the coil generate more heat, which if I understand correctly can be a detriment to the lifespan of the coil. I'm rather ignorant of how a coil works, but the gentleman I talked to today said he installed a standoff for his coil on the A4 and it reduced the temp by getting it farther away from the block. I'll try reducing the gap and see if I generate a stronger spark.

Man, this forum is really something for its combined experience. Wonderful!

I have attached a picture totally unrelated to the discussion at hand, but sailing-related for sure--my wife sailing our Ranger Minto about two hours before the motor stopped working.

[robshepherd]

Back to your buddy's theory of voltage drop to the coil during cranking, the coil only needs 9 volts to function. At that voltage you wouldn't be cranking at all so I'm discounting the idea.

Ah. OK. I don't have a voltmeter, other than the analog unit installed, but I'm sure I've got more than 9 volts available. I have a 40-watt solar panel on a charge controller, and I can turn on nearly all of the cabin lights without any dimming.

I'm cranking at a brisk rate, and from your comment I gather that it takes considerably more than 9V to do so.

Good to know! Thank you Neil. -Rob

[hanleyclifford]

If you are going to continue to travel the points/condenser route with your A4 I recommend you obtain a dwell/tach meter at your favorite auto boutique. It is dwell, not gap, that is the important specification.

[robshepherd]

pts/condenser vs. electonic

If you are going to continue to travel the points/condenser route with your A4 I recommend you obtain a dwell/tach meter at your favorite auto boutique. It is dwell, not gap, that is the important specification.

I will read up on the differences between dwell and gap. Thanks. As for the pts/condenser route, I'm rather on the fence. Points aren't cheap, and for me at least they don't seem to last more than a year. That's to say that if I replace them after a year I have much easier starting and generally smoother running again. The electronic ignition appears to simplify things a bit, and I'm always attracted to that. Is there any good reason to NOT convert? Thanks! -Rob

[hanleyclifford]

I will read up on the differences between dwell and gap. Thanks. As for the pts/condenser route, I'm rather on the fence. Points aren't cheap, and for me at least they don't seem to last more than a year. That's to say that if I replace them after a year I have much easier starting and generally smoother running again. The electronic ignition appears to simplify things a bit, and I'm always attracted to that. Is there any good reason to NOT convert? Thanks! -Rob

Yes. You must be unusually stubborn and enjoy futzing with points and dwell meters.