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  #1   IP: 76.109.12.62
Old 01-04-2010, 01:37 AM
SailorT SailorT is offline
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Engine will not run below 2000 rpm!

Hello fellow A4 sailors!

For the past six months, I've been struggling with problems in my fuel system, which have been caused mainly by the excessive debris in the fuel tank. I'll tell the story in reverse since I'd like to hear what you all have to say about my current problem.

Right now, the motor starts with a heavy throttle and cuts out if I bring it down to 2000 rpm. This happens when the engine is cold or at full operating temperature, with the choke on or off. I have adjusted the idle mixture screw, from 1/2 a turn out to 4 turns out, but with no change.

I am currently using an plastic outboard tank with fresh fuel. I have a racor filter/separator feeding an electric pump followed by an inline filter before the carb. I recently removed the carb, took it apart and cleaned it (before I did this, the engine would only run for a few min before dying).

Now for some history ...

About six months ago, I had the tank removed and chemically cleaned after I looked inside and discovered about a half an inch of debris in the bottom, including an old pickup tube which had broken off years ago. I was there when the guys removed the tank (and when the 4-5 holes in the bottom of the tank showed themselves!), but I wasn't there when they put it back in, so I didn't get to inspect the inside before it was re-installed.

After the tank cleaning, I removed and disassembled the carb and gave it a thorough cleaning. I added enzyme stabilizer to whatever I fuel I put into the tank, and tried to keep it as full as possible to avoid condensation build up. This seemed to solve the fuel system problems, but with time the engine began running poorly again, and then had problems starting. A couple of months passed where the boat sat idle and more than likely condensation built up in the tank again.

In December, I began working on the boat again, specifically on getting the engine to run again. Suspecting water in the tank, I collected a sample from the racor and the fuel was the color of apple juice, as it had been when I had the tank cleaned back in July. I disconnected the fuel line from the tank and fed it into a jerry can of fresh fuel and the engine started (and restarted) and ran for about 15 min.

I drained the entire tank (it was full, naturally) and inspected the inside through the fuel gauge sender port. Although it was much cleaner than six months ago, there was still a substantial amount of debris in the bottom. I employed the plastic outboard tank expecting better results, but the engine would not start consistently. I recognized the symptoms of a dirty carb and so begrudgingly removed it, again, disassembled it, again, and cleaned it, again.

After a few tries, the engine started with the choke out and about 1/3 throttle. I let it get up to operating temperature and pushed the choke in and let it run some more. No matter what I do, the engine will not run below 2000 rpm.

My hunch is that there is still some blockage in the idle jet, but before I switched to the outboard tank and took the carb off, the engine ran at normal idle speed, although not consistently. The only other thing I can think of is a vacuum leak, but again, the 2000 rpm problem is new since the latest carb cleaning.

Right now I'm considering purchasing a rebuilt carb from Moyer to start fresh.

I look forward to all your wise and learned advice on this issue.
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  #2   IP: 75.178.66.95
Old 01-04-2010, 09:56 AM
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Marian Claire Marian Claire is offline
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When I removed and cleaned my tank I was surprised at how much crud was still in the tank after a great deal of flushing and power washing. I had to cut an access in the tank, a very exciting procedure, and scrub it with a brillo pad. I would check the carb for air leaks. You can use carb cleaner. Carefully spray some around the carb to manifold connection, the throttle shaft, the joint between the carb halves and listen for a change. Is this a four screw carb? If the carb is working properly excess air could cause your symptoms. Also check the choke position and function. If the choke is actually closed and she will run at 2000 RPM you either have to little fuel or to much air. I believe the main jet takes over around 1200 RPM. So if the idle jet was blocked, but the main jet is good, you should be able to get her down to 1200 RPM. Do you have the fixed or adjustable main jet? More rambling than wise and learned. Dan S/V Marian Claire
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  #3   IP: 75.67.203.22
Old 01-04-2010, 12:24 PM
riphonda riphonda is offline
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New Carburetor

Sailor T,

If you noticed that there was a big difference in the operation between the time you ran with dirty carb and the time you cleaned it, it makes sense that you have a pretty good idea that your carb is fouling up the engine. I have a 1976 that would run intermittently with the existing carb and i even spot cleaned it numerous times at which point it seemed would run a little better each time but eventually would again go kaput. I ruled out some other things first like: does the engine have spark? Does the engine have compression? Does air get thru the flame arrestor? (not too good so I cleaned that too with a wire brush and some detergent/water). After answering those questions I was onto the solution. Now what to do: I looked at Moyer's carbs and decided to just go ahead and buy the new one for a few bucks more and I have been happy as a clam with the carburetor. It was a bolt and go. At the same time I replaced all the fuel hose and the tank as well as added a new facet electronic pump and filter. Engine runs great and the best part: since installing the new carb I have not had to clean it a single time! No gas on the hands and no mess.

I hate to say to get the most from the engine you might as well just go ahead and spend the money (I can be the king of cheap) but I have been much happier having spent the money than I was fumbling around with a shabby old carb, gummed tank, fuel lines and temperamental engine. Time has been mucho happier sailing and bumming around than it was every weekend with wrenches and gasoline strewn about the cabin. And since I have made almost all the other upgrades to the engine offered by moyer. Only one left to go is the fresh water cooling. Not tellin' ya what to do, just throwing another success story into the mix.

Value always remains long after the money has been forgotten... Thumbs up to Moyer Marine for all the support as well.

Last edited by riphonda; 01-04-2010 at 12:27 PM.
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  #4   IP: 76.109.12.62
Old 01-10-2010, 09:34 AM
SailorT SailorT is offline
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Solved the problem

Hello again!

So after doing some head scratching and following a hunch, it appears as though I've solved my problem. It looks like not using a full main bowl gasket was causing the headache.

When I removed and disassembled the carb last week (see my intro post above), the main bowl gasket broke apart and I was not able to reuse when I put the carb back together after the cleaning. In the interest of expediency, I did a field mod and used silicon rtv gasket maker to seal the upper and lower main bodies together since I didn't have another main body gasket on hand. As I scraped away the old gasket, I contemplated what effect not having a complete gasket would have on how the engine would run. I noted that none of the internal chambers of the carb were completely separated by the gasket, but that the flow of air between them appeard to be regulated by the gasket in some ways. I resolved that whatever effect the increase in airflow had on the engine's performance I could counter by adjusting the fuel flow, i.e. if the carb draws more air, give it more fuel. I figured that this would work long enough to get me out of the shipyard and into the marina, where I could install a proper gasket at a later date. Or so I thought ...

After encountering the 2000 rpm problem, I realized of course that the missing gasket was the most likely problem, and called Ken at Moyer to discuss the issue and quickest way he could send me a new gasket. After realizing the $5 gasket would cost $5 to ship, I searched for local stores that might have the gasket, but had no joy.

I was about to call Ken back when I remembered a problem I had with one of my Jeeps years ago where I needed a gasket that was not readily available ... I made my own.

So, in the interest of time, I bought some gasket material at the nearest NAPA (still like NAPA stores over the others - no polish, no wax, no chrome ashtrays, just straight to business mechanical parts and supplies!). I then went back yesterday to test my theory, and my skillz! I took with me a pic of the gasket from the Moyer online catalog for reference.

After some careful tracing, cutting and shaving, I had my gasket. I had to eyeball where some of the internal holes were since they didn't make a strong impression when I pressed the cut gasket onto the lower and upper main bodies. I was happy with the results, and had high hopes of success ... although I was also thinking of what the hell I was going to do if this didn't solve the problem!

I put the gasket in (with a little gasket sealer), put everything back together, reinstalled and reconnected the carb. After about a min of cranking with the choke closed, the engine started right up! I let it warm up by leaving it at 2000 rpm for a few min. Afterwards, I opened the choke and adjusted the throttle to see how low I could go. It went down to below 1500 rpm without a problem! After some adjustments to the idle set screw and idle mixture, I finally got it down to about a 1200 idle in neutral which lowered to about 900 in forward gear. Success!!!

I'm sure once I adjust the timing I will be able to bring the neutral idle down some more, but I'm happy with the 1200!

I've added some pics from yesterday, but you won't see the low 40 degree rainy weather that was going on at the time!
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  #5   IP: 71.252.8.223
Old 01-10-2010, 11:43 AM
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sastanley sastanley is online now
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Nice work with the 'build-a-gasket' SailorT!

Sounds like Dan's theory was correct...the busted gasket was causing an air leak.
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