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Old 30-08-2006, 16:20   #16
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More ideas...

Fuel tank venting properly? Mud daubers? Is there a loop in the hose? If so, it should be postioned so it won't trap fuel in the loop. Crack the tank fill open every few minutes to ease any pressure. You may hear suction when cracking it too. Just be careful of gas fumes going kaboom.

A long shot but...a clogged exhaust will stop the engine but it usually chugs hard before shutting down. If it doesn't chug it is highly unlikey the exhaust is restricted enough to shut it down...If you have an exhaust shutoff valve (usually installed in the exhaust pipe at the transom to keep water out in bad weather) check it.

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Old 30-08-2006, 17:30   #17
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First, all are good suggestions. The vapor lock issue is one that afflicts many of the a4's in part, due to the downdraft carb. If your fuel line runs anywhere near the engine top end, that is your most likely culprit. Also, if the fuel line runs through a lazerette, check that you have not set gear on it, and restricted the line. Air starvation is also possible, but not very common, as the A4 draws very little air.
As for the coil, most automotive ignition coils are not 12 volt. Thye are 7 volt, and use a balast resister to reduce the voltage. They will run on 12 volts for awhile, but will have a greatly reduced lifespan. A coil will generally fail completely, but on occasion, they will work until they heat up. Make sure the coil on your engine is a 12 volt coil, and has 12 volts running to it. Now, for the kicker. You mentioned your Volksie. We were on a raod trip in our 70 Westie, and were crossing a mountain range. The engine started cutting out. It made it the next 120 miles, but with a very agrivated driver It finally dies in a parking lot in a small town. Too late to get parts. I figured it was a fuel problem, but as I was messing with the fuel system, I accidentally discovered the problem. The hot wire to the coil had minor corrosion inside the connector. It was not visible, but when I bumped the wire it ran. I cleaned, the connector, and crimped it a little tighter onto the coil, and it has run fine ever since. A wordy way of saying, check your connections

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Old 30-08-2006, 19:07   #18

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Kai Nui's talk about pinching off fuel lines made me realize there IS one thing that can stop an engine which we've totally missed. The fuel tank VENT LINE!

If something is clogging the vent line, like a spider or wasp nest in the vent for it, the engine will run just fine, sucking down a vacuum in the tank until it can't suck the fuel any more. Then die with a wimper. As it dies, the vacuum in the fuel tank slowly releases...and it will start up again without any problem.

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Old 30-08-2006, 19:40   #19
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Kai, the carburator is updraft. Meaning the fuel mixure travels against gravity up into the manifold intake valves. The restrictor plate related to "stevedore" is in the manifold. So all one has to do is get another used manifold. Dave, with my A4 I ended up changing bunch of wires at first and the re-wiring the entire engine room. Definately re-wire parts of the engine. I can tell you from experience that ignition wire from ignition key(start position) to starter solenoid should be new with new connector on the solenoid. Clean out the solenoid terminals as well and you should have the starter out for that . All wires to and from the coil should be replaced. Wirebrush or sand the grounding areas on the block as well as terminals on the coil and alternator. Re-crimp new connectors, and take the old non-ABYC non-marine wires out. They were not oil resistant and they are so brittle you can break them by hand. Have you looked into external vs. internal resistor coils? The new coil burns out fast if you buy the wrong type. My original one was with internal resistor so my subsequent coil had a label "for use without external resistor". I learned that the hard way.
One other thing I did is add a 10A fuse in the ignition circuit from igintion key run position to coil +. One time while motorsailing the engine died and I didn't turn the key off so after about 5 minutes that wire almost ended up catching on fire! I had thick white smoke fill up the cabin from the melted white wire insulation. The following off season I ripped everything out and rewired the entire boat(fused up everything and installed larger gauge marine wire)
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Old 31-08-2006, 05:27   #20
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To clarify...The vent line I posted about is the same one hellosailor posted about.

I've used both internal and external resistor 12V auto coils on boat engines for yrs without a problem. If the external resistor is left off it cooks the coil, wires or blows fuses, etc...if you don't see it you will smell it. When coils get hot enough to fail it is very rare to have them start right back up until cool.

Just my opinion but if the motor is running smoothly and suddenly stops I'm skeptical of it being vapor lock. Especially since it starts right back up without a problem. Regardless, have you changed to ethanol fuel lately? It's more prone to vapor locking and can make a difference.
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Old 31-08-2006, 19:40   #21
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Petar, I stand corrected. It was a mis-speak, but I knew what I meant.
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Old 31-08-2006, 23:47   #22
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Atomic 4s

That little tube in bottom of the "air intake" is a 'sniffer port' so that if you get any drips of gasoline falling down from the updraft carburator they will quickly get 'sucked' into the intake manifold .... instead of collecting in the air intake (flame arrestor) - its a 'safety suction port' that helps the engine and boat from going 'boom' if the carburator starts to (very very rare exception) drop gasoline down the wrong way in the updraft carburator.

#1 Your symptoms sound similar to a dirty emulsion tube in the carburator. The emulsion tube is approximate 1 inch long by about 1/8" diameter and sticks down into the main jet well. There will be two teeny holes in the side of the emulsion tube and ***ANY*** dirt that gets stuck in these 'side orfices' of the emulsion tube will give symptoms similar to yours. That you cleaned and changed just about all the fuel components suggests that you might have dislodged some 'crap' and that its now stuck in these teeny side orfices of the tube. The emulsion tube controls the atomization of fuel before it gets drawn into the venturi section ... if the 'emulsion' (frothy gasoline) isnt correct you will get all sorts of 'fuel system' variability ... stalling, rough idling, rough running, etc. ... sometimes yes, sometimes no ... but never 'constant'. Simply look for teeny small flakes of rust, etc. in the tube and the 'side orfices of the tube', etc. ..... and be sure that the internals of the emulsion tube and its teeny side orfices are clear and 'spotless'. **ANY** 'crud' in the side orfices of the emulsion tube will yield a very rough and non-constant running engine.

#2. When you spoke with DonM did you discuss the 'match up' of ignition coil with your primary circuit in the distributor. You dont mention if you have the old fashioned 'points & condensor' set-up or a newer solid state (electronic) ignition. The newer solid state ignitions can not be used with the older coils used with 'points and condensor' as the coil will quickly overheat and malfunction. Is the coil 'matched' with the primary circuit of the distributor????

#3 There should be a gasoline tank vent that opens to atmosphere somewhere on the outside stern of the boat. The tank vent *should* have a stainless screen (spark arrestor) over the opening to the vent ... and the whole vent 'system' opening should be covered with a small metal 'cowl'. Spiders LOVE to spend their daylight hours inside these types of vents and their webs, nests, egg-cases, etc. will easily block such a vent.

#4 Whats the status of the *engine ground strap*. There should be a large braided stainless steel 'strap' from the engine to the main ground (ultimately connecting to the battery negative). If there is any corrosion or failure of the wire in the 'ground strap' or its connections due to years of accumulated engine vibrations or corrosion ..... the whole engine's electrical system will be 'sporadic' until the 'ground connection' ultimately and totally fails. Check the electrical continuity of the engine's "grounding (not bonding) circuit". If you dont know how to test for 'continuity', just run a temporary wire (8 or 10 ga. or "heavier") from the engine block (flywheel housing bolt, etc.) directly to the negative of the battery and see if this doesnt "improve things".

Hope this helps.
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Old 03-09-2006, 12:00   #23
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I had been checking this thread but, hadn’t figured out it had gone to page 2… Doh!

Anyways… here’s the update. I was finally able to get to the boat yesterday and run the engine. As a reminder, I changed the points and fixed something on the coils ground wire that didn’t look right but, didn’t have time to run the boat. This is an old school setup… no electronic ignition. So, the engine ran at the dock while in drive for 45 minutes yesterday. Then we went for a motor cruise for about 45 minutes as well. No problem and engine seems fine now.

I kinda think it was the ground wire / condenser wire connector at the points. It also may have been that weird looking thing I saw on the coils ground wire as well. It was a metal snap ring that was crimped on the insulation. It didn’t make continuity to the wire itself at the time I measured it. If it did, when it got hot, it would have shorted to the distributor housing.

Thanks again for all the help and suggestions. For sure I need to fuse the ignition system. I don’t think there is any.

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Old 03-09-2006, 12:22   #24
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It is quite possible the points were the culprit. If either not set properly or burn't or worn enough that dwell time is too long, then these faults can all heat up the coil or cause running problems.


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