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  #1   IP: 75.54.193.51
Old 10-01-2020, 12:57 PM
trevvahhh trevvahhh is offline
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Suddenly died at at idle, now doesn't want to idle

Hello all!

Humbly making my first post here, I have been lurking the forum and found the answers to many a question in getting my new to me A4 in decent order. It's my first boat and while being sold as a "reliable and well maintained" A4, it's been anything but so thank you to everyone who posts here and to the hosts.

After getting the engine starting well and replacing the entire exhaust except waterlift to fix a leak in the old hot section, we took the boat out to test it yet again, idled great out of slip, ran good under power, came back to idle and was about to put the sails up when the engine died and wouldn't restart. Had to get towed back to slip

Got engine started again an hour later back at slip, but it wants to die at idle and runs a little rough, issues we weren't having before

between PO and the guy that has been working on the boat, things get a little jury rigged

New plugs (RJ12c)
recently changed to a generic electric fuel pump 2-3.5psi
no OPSS (on the way)
tank is in unknown condition
Carb was gone through recently not by me but could be gunked up at this point
fuel filter and hoses appear recent but temped to change filter

The engine was underwater for a short while (trying to keep this brief ) they changed the oil a few times and got it running again, but the day these problems started i added MMO to the fuel tank, and its possible I added too much as I was unsure if we had 5 or 10 gallons in the tank (dipstick read 11 but we added only 6 the other day after we thought we ran out of fuel, maybe we didn't run out or the dipstick is wrong) I added 6-7oz of MMO trying to split the difference

Anyway, I am posting some videos of the engine dying at idle, clicking a bit, and throttle up and down. I am going down today to troubleshoot the fuel system but thought maybe the experience here might glean something quickly from the videos. I'm a first timer at all this but having fun although my wife is over it.

going to try to run off a funnel or different tank and see if that helps then work my way back. will probably pick up a cheap fuel pressure gauge and install the oil pressure gauge i bought as the orig is shot and I have no idea of oil pressure at the moment

Thanks for any insight! hope everyone is well and thanks again for all the info over the years, it has helped a ton

-Trevor

dying at idle - https://youtu.be/OJw8uMNEblo
throttling up and down - https://youtu.be/FGf2qnlEQKo
clicking sound at low-ish throttle - https://youtu.be/Mm-P8XlnQ_I
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  #2   IP: 32.211.28.40
Old 10-01-2020, 04:19 PM
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Al Schober Al Schober is offline
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Curious how it died the first time. Did it sputter and stumble for a while or did it stop like you turned off the key?
Next time it dies, I'd first check for spark. That will give you a direction to proceed for further testing.
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Old 10-01-2020, 05:44 PM
trevvahhh trevvahhh is offline
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thanks for the reply! it was a sputter and stumble type situation for sure. heading down now to check it out, will double check for spark. can it still be an ignition issue if it is running albeit roughly? the guy that worked on the boat kind of fixed a bolt in the distributor/points with a random hinge bolt but got it back working, I think we are def on borrowed time before electrical ignition switch
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Old 10-01-2020, 05:59 PM
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The YouTube videos in the original post are very instructive.

Bill
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Old 10-01-2020, 06:25 PM
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Do you have a water separator. If so drain it and see if you get water. Also ensure the fuel fill cap has a good gasket. My very first suspicion listening to the first video is water in fuel. Obviously the engine is starving and it was running well prior, it runs well and could be getting water bubbles coming through the carb.

The ticking...the engine doesn't sound bad at all. Not sure where that ticking was coming from but almost sounded like the accessory gear. Try putting the phone back in the area of the dipstick and raw water pump and see if it is louder there...whatever it is doesn't sound terrible at this point. Also look for spark arcing...sometimes a spark plug will chafe somewhere and tick as the electricity flows through it.

Hope that helps.
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Old 10-01-2020, 08:03 PM
TimBSmith TimBSmith is offline
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I listened to "a4 throttling up and down" at .5 speed..curious stumble..

Something curious about firing at timestamp :40. I am just getting to know this engine. (I have been shaking down mine since August 2020, typical boat on hard, no PO history at the time.) I went through fuel top to bottom, ignition/compression, and now cooling system (looks like I will be replacing the black pipe stack). Now back to you....

My untrained ear hears something off at the bottom of the throttle down then up. A skip, tap, miss kind of pattern break, like either a serial timing or spark step fail, or an intermittent fuel starvation. It does sound a little too cyclical to be fuel water but I will leave it to more experienced ears to add diagnostic value. Worth a listen even if I am completely wrong.

It is curious how the engine can have a cadence and slowing video way down or way up can help with diagnostic. Best with trouble shooting. You (and we)are in great hands here.

Stay well, Tim
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Old 10-01-2020, 08:23 PM
TimBSmith TimBSmith is offline
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"a4 clicking low throttle" listened at .50 speed at :14 seeing exhausts plumes

I see evidence of exhaust puffs parallel to plug 4 and then toward the back of the manifold. I have read a lot about blowby and while this may not be determinative I am wondering how compression is because I recall "engine sputtering" can be one consequence of blowby. I am cautious to suggest this, and learning here how important it is and how to patiently isolate and differentially diagnose systems that are both separate and interdependent.

You mentioned that you worked on the exhaust system hot side and wet but not waterlift. How have cold and hot compression been in cylinder 4? Has compression held up or degraded over time? Using much oil? I wonder how exhaust pressure has held up over time. I wonder about ring health. Maybe worth a look in addition to fuel focus. First time I ever checked an engine's compression was on my A4. Seems to be at the top of most diagnostic trees.

Stay well, Tim
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Old 10-03-2020, 01:45 PM
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I can only add my anecdote about engine not idling. It turned out to be a tiny blockage in the idle jet. Not visible until jet removed and held up to the light. Carb cleaner did not dislodge it, but a wire from a wire brush did.

Last edited by capnward; 10-04-2020 at 12:02 PM. Reason: spelling corrected
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Old 10-24-2020, 07:30 PM
trevvahhh trevvahhh is offline
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Been a crazy few weeks but just wanted to update and say thanks for all the replies. Looks like Mo was spot on, I pumped some fuel into a jar just before the carb and there was a small amount of water in the fuel. worked my way back using an aux tank with good fuel, replaced the water separator filter, and was back to running relatively smoothly. hoping that it was just a result of condensation in the tank since the PO only had about 5 gals in the 20 gal tank for who knows how long. tried to filter out what i could of the tank pumping through a water seperating funnel and added fresh gas.

has been running great until it shut off abruptly and wouldn't start last night a mile with out with my wife and two year old, but that's a story for another thread if I can't glean enough info from existing threads

endless thanks to all for both the info and community here! getting a quick introduction to the joys of boat ownership

-Trevor
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  #10   IP: 134.41.92.9
Old 10-24-2020, 09:01 PM
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If the engine shuts off abruptly, as if you turned off the ignition, the first thing to do is check and see if you have spark at the spark plugs. Sometimes there will be absolutely no spark if checked immediately. What can happen is the coil heats up and fails, then after a period of time (sometimes half an hour to an hour) it will start as the coil cools....and run well until it heats up again. Other causes of an abrupt shut down are ignition wire bad connection and failure of ignition components such as points and condenser or EI module. Usually it's a coil issue when underway though.

A sputtering shutdown usually leads me to think fuel issue. A sudden shut down ignition issue.
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The pessimist complains about the wind.
The optimist expects it to change.
The realist adjusts the sails.
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