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  #1   IP: 63.136.233.38
Old 04-14-2011, 05:46 PM
Mike C Mike C is offline
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Low-Throttle Stalling - blocked idle jet, bad fuel, choke?

Looking for inspiration to troubleshoot the latest challenge.

History:
I've had my A4 for about a year and a half. When I bought the boat, the A4 looked to have been rebuilt and, from the outside, looked to be otherwise fairly well maintained. When I bought it in October 2009, we motored it for the better part of two days without an issue. Worked fine until early last summer, when I discovered the hard way that the cooling system had a few problems - blockage from crud internally, the underside of the thermostat housing had corroded badly, and the mufler leaked, which all led to an brief overheating incident. That taught me the difference between steam and smoke from burning oil.

Maintenance:
Cleared the cooling system blockage, replaced the thermostat housing, installed a new MM SS water lift muffler, and replaced all the water hoses.

Good times/Bad Times:
The engine worked well for a few more trips but one day in September/October, it stalled when I put it in gear and woud only run in neutral. Next time, it was worse, hard starting. Eventually, I got it running by using starting spray into the carb intake.

My belief at the time was that it was a carb issue so I bought and used the carb rebuild kit from Moyer (and also changed the fuel filter). The engine's behavior changed dramatically. It roared to life when started like never before - but would only run at high throttle and stalled in idle. Unfortunately, the winter set in before I could do any more and I had to winterize it and wait until now.

I'm heading off to spend another day on it and still thinking its a fuel delivery issue. I've got a few hunches based on other threads I've read here and a suggestion: (1) idle screw adjust - try counter clockwise adjustment; (2) blocked idle ject - try carb cleaner; and (3) water in the fuel and likely worse now that the fuel sat for five months - replace all the fuel.

I would really appreciate any thoughts or suggestions, particularly as to which I should try first, or not try at all, or if there is another diagnostic think I can do to sort it out.

Thanks much,

Mike
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  #2   IP: 12.166.158.242
Old 04-14-2011, 06:41 PM
Kurt Kurt is offline
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Sounds like your diagnostic thinking and action plan are on target to me. The only thing I can think of that you should keep in mind (if everything else you mentioned fails to solve the problem) is a leak (vacuum leak) at the exhaust manifold gasket area or where the carb bolts onto the manifold. These areas both have gaskets that can fail, causing a vacuum leak and bad engine performance at idle. You can check this by spraying carb cleaner around the gasket areas with the motor trying to idle and if your symptoms improve, you have found your culprit.
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  #3   IP: 173.20.99.40
Old 04-14-2011, 06:42 PM
sailhog sailhog is offline
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Mike,
Did you have an ethanol blend in your tank when you laid her up? If so, the fuel will probably have to go. Empty your Racor and polishing filter, as that fuel is probably separated as well. Clean out all your lines.

I've been through a similar (but more extensive) process recently.... I'd also get MMI directions for cleaning the carb. Yank it, take it home, clean it with carb cleaner, compressed air, tiny wire for the tiny ports....

Make sure your choke is completely operational. I neglected this at the beginning of the process. Don't make the same mistake. Make sure it closes completely and opens completely -- from the cockpit.

It sounds like a lot more work than it is. Get a list of all the parts you'll need, then get to work.

Best of luck to you.
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  #4   IP: 24.224.206.117
Old 04-14-2011, 07:35 PM
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Hi Mike,

I would have been thinking water or dirt in the fall episode.

Question: Were you in rough seas or chop when this started happening.
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  #5   IP: 76.106.2.171
Old 04-14-2011, 08:58 PM
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The facts of the matter seem to be these: you replaced the carb in October/November of last year, and it roared to life but wouldn't hold in low idle. You never followed up on this and now are wondering about what to do for this season.

First off: ignore the entreaties to replace your ethanol blended gas and clean the tank, at least until you've investigated other possible causes. I've had my A4 since 2007, have left full tanks of E-10 (the blend you get at gas stations) in my engine over every winter, and have never ever had a problem getting her to run in spring.

So start with this: leave the raw-water through hull closed and try to start the engine after performing all the normal spring start-up procedures. That will include an oil change and new plugs, or more, though plugs and oil are all that I've ever done.

Get the tools you need to perform a low idle adjustment -- probably just a regular screwdriver, though if you are lucky and your PO put in the new Moyer idle screw, you can do this with your fingers.

Start the engine the way you normally do, with your usual choke and throttle settings. If it starts, let it warm up a bit, then push the choke in and idle down as far as she'll go without stalling. (Don't forget to open the raw water through-hull once she's running!)

Now begins the dance: turn the idle adjustment screw in a half-turn (tightening that screw down makes the idle mixture more rich) and wait a few seconds (15-30) to see what happens. If the RPM increase, throttle down to where she'll just hold again and repeat. If the RPM decrease, turn the screw back and then another half-turn out and see what she does then.

Every time you get the RPM to increase by going one way or another, let it stabilize and then throttle down again as far as she'll go and make another adjustment. What's happening is that as you get the idle mixture closer to the ideal, the throttle idle will be able to go lower and lower without stalling. I performed this exercise after replacing my carb in 2008, and now she'll hold in gear at about 400 RPM or so.

If none of this works, you may well have a carb blockage, in which case you'll want to take it off (a very easy procedure: two bolts, the scavenger tube and the throttle and choke linkages) and clean it thoroughly,, and then try again. Those procedures can also be found in this forum.

Good luck, and keep us posted!
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  #6   IP: 24.224.206.117
Old 04-14-2011, 10:36 PM
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Smile Excellent approach.

Good start there Baltimore Sailor Excellent approach at this stage of the game.
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The pessimist complains about the wind.
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The realist adjusts the sails.
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  #7   IP: 216.115.121.253
Old 04-15-2011, 03:07 AM
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Another thought

Some old rubber fuel lines can start to crumble from the inside. Every time you clean the jets, the engine teases you with running for a short while 'til another little piece falls off, comes down the line, and gets stuck in the idle jet.

Baltimore is on it. Do that stuff he says what to

Russ
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  #8   IP: 173.166.26.241
Old 04-15-2011, 10:37 AM
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hanleyclifford hanleyclifford is offline
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Talking

While I agree with Baltimore Sailor's approach to adjusting the idle I would add only this. IMO every sailboat tank in the fleet should probably be purged and cleaned in one way or another due to the influence of ethanol which is cleaning the fuel systems for us whether we like it or not, and depositing the proceeds down stream to you know where. This is an on going process. There are only two exceptions to this recommendation. 1) The engine is run year round and is running well. 2) Like me, you have the old fashioned bottom drain (no longer Coast Guard approved).
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  #9   IP: 74.96.53.114
Old 04-17-2011, 08:19 AM
Mike C Mike C is offline
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Making Progress

Thanks to everyone for all the outstanding suggestions. After changing the oil and checking the plugs (new in October with only an hour or so of time on them), I checked the throttle and choke cables. Found the throttle cable had come loose from a bracket. Started up after a few tries and confirmed we were where right we left off - engine would only run without stalling at about 1/3 throttle. A passerby observed that there was unburned fuel in the exhaust and thought the mixture was likely too rich. However, using Baltimore Sailor's method, I was able to improve things by making the mixture more rich, getting to the point where it ran with only a little throttle. I think I was about 95% of the way there when oil started pouring out of the bottom of the engine. Shut the engine at that point. I did not have the presence of mind to monitor the oil pressure gauge while I was working but I am hoping that the leak was just a result of me neglecting to tighten the oil fill hole's bolt/cap sufficiently when I changed the oil. I tightened it more. The sun was down and a good storm was raging outside, with heavy winds, rain, and lightning, and the wife was losing patience. After cleaning up the mess, I had to call it a day. I'll go back tomorrow or Tuesday to examine the oil situation in better light and continue with the idle adjust. Thanks!
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  #10   IP: 50.14.226.196
Old 04-17-2011, 10:19 AM
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Quote:
Originally Posted by hanleyclifford View Post
...There are only two exceptions to this recommendation. 1) The engine is run year round and is running well. 2) Like me, you have the old fashioned bottom drain (no longer Coast Guard approved).
Hanley-
I'd like to suggest a THIRD exception if I may...
3) You are lucky enough to have not used any ethanol laden fuel.

(Although, if exception #3 applies, then you may also have exception #1)
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  #11   IP: 173.166.26.241
Old 04-17-2011, 10:48 AM
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Thumbs up

Quote:
Originally Posted by roadnsky View Post
Hanley-
I'd like to suggest a THIRD exception if I may...
3) You are lucky enough to have not used any ethanol laden fuel.

(Although, if exception #3 applies, then you may also have exception #1)
Thank you Jerry. I stand corrected..er supplemented..Exception #3 is actually the happiest situation of all. Wish I could be there!
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  #12   IP: 63.136.233.38
Old 04-18-2011, 01:26 PM
Mike C Mike C is offline
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Oil Leak = Fuel Pump Leak?

I apologize for expanding the scope of this, and I hope my imagination is not running off, but I had some questions.

Issue 1: The volume of oil that suddenly leaked from the engine seems inconsisent with an intact, but somewhat loose, plug. Also, how or why would the oil rise from the pan in quantity to exit through the threads of the plug? I looked at Don's list of likely oil leak locations on the carb side of the engine and will inspect those asap. A sudden breach in a seal or gasket is a possibility, I suppose. But why now, sitting in the slip at relatively low RPM without any load or shocks?

Issue 2: I assumed the fuel mixture being rich was the source of the unburned fuel in the exhaust water but to improve the idle, I made the mixture even more rich, which would seem to not be a good thing so far as the amount of unburned gas in the water goes. Could there be a connection between the oil flowing out of the engine and the unburned fuel? On the MM FAQs page is an entry indicating that a hole in the fuel pump diaphram could cause both a rise in oil levels and unburned fuel in the exhaust. Would a hole in the fuel pump diaphram also cause the fuel pump to be less efficient, maybe causing the engine to lose some % of its power, perhaps demonstrated by stalling when put in gear or only running with a rich mixture/elevated throttle?

If a diaphram leak causes the oil level to rise, could it rise enough to find a way out of the engine? When I change the oil, I thought it smelled of gasoline, but dismissed it as a misperception. However, oil smelling of gas is one indicator of a fuel pump diaphram leak. If I pump out some of the oil now, I guess I can take another whiff.

What might the significance be of the new spark plugs being unevenly sooty, with the first being quite clean and the last two being more blackened?

Thanks,

Mike
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  #13   IP: 24.152.131.220
Old 04-18-2011, 04:39 PM
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Mike,

I'd suggest taking on these things one at a time. It sounds likely you have a fuel pump diaphragm breech. By design and in compliance with USCG requirements, the fuel is dumped into the crankcase rather than the bilge. A check of the dipstick for increased level and a sniff of the oil on the dipstick for a gasoline smell should confirm your suspicion. As you continue to pump fuel into the crankcase the level will rise to a point where it will find a way out. This is a condition that's impossible with an electric pump.

I'll leave it to others to comment on the uneven plug condition.
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