Atomic 4 shut down problem - SailNet Community
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post #1 of 28 Old 08-20-2007 Thread Starter
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Atomic 4 shut down problem

I have a '78 atomic 4. I have replace the fuel pump and filter. When I run for around 2 hours it just shut down , like it's getting a vapor lock, I give it a rest and it will restart . any ideas?
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post #2 of 28 Old 08-20-2007
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i'm no expert, but even i need more info. Is it a gas or diesel engine? how long a 'rest' is required. complete cool down or just a 5 minutes? have you tried checking the fuel tank vent? is it clogged? what if you open the tank immeidately after shutdown is it stuck tight? does it make sucking sounds?

if gas: how old is the carburator? how clean? how about the points are they old ? foulded?
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post #3 of 28 Old 08-20-2007
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If it doesn't restart right away, I would look at replacing the coil. If it does start up again right away, look to see if the vent is clear. After that, look at the fuel itself. If it's an ethanol blend and you haven't added a fuel stabilizer, it could have degraded. The other likely possibiilty is the carburator. I've been having the same trouble with mine, and I have yet to completely solve the problem. It could be fuel starvation, but it's definitely not vapor lock. I'll be monitoring your progress...
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post #4 of 28 Old 08-20-2007
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jldooley-

Atomic 4's are all gasoline engines.


Have you checked the fuel filters? Do you have a fuel/water separator? Have you checked the fuel tank vent line for blockages?

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post #5 of 28 Old 08-20-2007
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It's August. I would go with spider webs in the fuel vent line leading to a partial block, which leads to negative pressure in the tank, which the measly 2 PSI fuel pump is eventually unable to overcome.

It's essentially a stroke, in engine terms.

Clean out the goo.

I would vote for the coil failing due to high heat as a reasonable second cause, all else being equal. There are mods (put the coil off the block on the bulkhead, increase the cool air venting to the engine compartment) that can remedy this above and beyond getting a new coil, which is not a bad idea anyway.

I would also clean the carb (or the "crab" as the late, lamented Qshicks, demi-god of Atomic 4 maintenance, called them), but this could just be a band-aid if you actually require a carb rebuild...this can be done, but is fiddly, close work.

Lastly, you should check the tightness (and the doubling) of all clamps and seals in the fuel circuit. If you have a fuel/water separator, make sure it's relatively new, has a greased O-ring, and is dogged down properly. If air is getting in there, it's more a case of an embolism than a "blood clot". This includes torquing down the bolts holding the carb and fuel pump to the block...if a gasket here is failing or "seeping", that could also lead to the cumulative effect you describe, but is less likely IME.
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post #6 of 28 Old 08-21-2007 Thread Starter
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Atomic 4 shut down

Thanks for all the great thoughts. The fuel has enzyme treatment - Fuel filter has been changed twice no water appears in the cup,- fuel pump new this yr.- Carb was rebuilt about 4yrs ago - the coil has not been replaced but it does hang off the front of the block by the alternator. I have tried running with the engine hatch open still have the same prob. I will look at the carb. and the coil.
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post #7 of 28 Old 08-21-2007
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Justified,
I know this is hard to really quantify, but how old is your fuel? I put fuel stabilizer in when the tank was about a two-thirds fully, and have still been having problems. I'm wondering if the problem is that there is still some old, degraded fuel in there that's causing the shut down. According to US Boat, the stabilizer isn't capable of stablizing fuel that's already degraded, so I might be SOL. I'm considering pumping all of the fuel out and putting it in my car since I don't give a **** about it. I'll fill up with fresh fuel and stablizer, and drive around the neighborhood with my bicycle in the back.
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post #8 of 28 Old 08-21-2007
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take this to the bank... replace the coil with an internally ballasted 12volt coil (about 20.00 at NAPA/Pepboys/autozone) chuck the ceramic external ballast (it also may be a "coiled" style resistance wire) overboard, replace with 10-12 guage primary wire and go sailing.

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CP,
Wouldn't the engine shut off abruptly, as though someone had turned it off? My problem, and I think Justified's problem as well, sound like a fuel starvation shut down. My engine at least just slows down, and then peter's out over the course of five or six seconds. Thoughts?
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post #10 of 28 Old 08-21-2007
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Sir, I have the 78 atomic 4 in a catalina 30. I had the same problem. I got lots of good tips from Moyer marine. These are steps I used to fix my problem. I removed the screen on the end of the fuel pickup in my tank. I added a racor filter after the tank,and finishing filter between carb and fuel pump. I had no filtering system from PO. I replaced the ignition wiring. This was old and had many plug connections. I understand these corrode and fail when they heat up. I also installed electronic ignition. This all cost some $$. Has been running fine since then. Best of luck to you.
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