#1
IP: 128.29.43.2
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Fouling All 4 PLugs
All,
Glad to hear from Mo that the overall fleet of A4s seems to be doing well of late. Unfortunately, I cannot claim that my A4 is thriving of late. All summer, I have been fouling plugs. All four of them, and quickly. As in, less than an hour of motoring under load with new plugs will yield four carbon-encrusted plugs. When I can get her started with a new set of plugs, she idles well and runs strong under load and will do so for several hours. I have tried both the Champion RJ12C and the Autolites from MMI - same result. Some background: 1. Late model engine on a C&C 27 Mk I. Original engine from what I can tell. New to me two years ago. RWC, running in cool Lake Champlain. 2. Season 1 chasing cause of overheating issues. Resolved by extensive flushing. Engine now does not get above 150 degrees under load so Holley t-stat never opens. 3. Season 2 chasing cause of sticking valves. Resolved by replacing faulty (paper) head gasket. Here is what I know: I. Compression was good in all four cylinders to start the season (90 +) II. I started the season with a clean fuel tank, and re-fueled with ethanol free 91 octane. III. I started the season with a new MMI coil which produces a good spark. IV. I have a modest fuel leak somewhere in the vicinity of the lower bushing of my carb. Carb does not leak while engine is running. V. I have significant amounts of soot accumulating across my transom in line with the "tailpipe" thru-hull. Here is what I don't know (among many other things about my A4): 1. Where do I begin the diagnostic testing to determine cause of fouling plugs? 2. Do I begin with checking for excessive back pressure? 3. Do I begin with adjusting the carb for the mixture? 4. Do I begin with re-checking timing? I don't yet have the MMI back pressure gauge, so I have not done #2 above. I have done #3 and #4 repeatedly. I am not very bright, so the "idiot proof" sequential, diagnostic tests that this forum is famous for providing, I think that is what I need. Thanks in advance. Brian |
#2
IP: 161.213.49.150
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Brian
A quick and easy one. Is the choke all the way open when you think it is? TRUE GRIT |
#3
IP: 71.118.13.238
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If the choke is fully open the first thing to do is fix the leak in #IV. An abundance of fuel will foul the plugs in short order.
Dave Neptune |
#4
IP: 128.183.140.38
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Excessively rapid plug fouling, and carbon soot on the transom, both suggest an over-rich fuel mixture to me.
Since you have a late model, it doen not have an adjustable main jet on the carb (unless you installed one). The "mixture" screw is actually an air-bleed adjustment (more open == more air) that only affects the idle mixture. As mentioned, an incompletely opening choke plate can result in an over-rich condition. Similarly, dirt in the carb float needle valve can result in the same thing. Since you report a fuel leak at the lower bushing, this would support the theory that the float valve is not shutting completely, allowing it to dump too much fuel into the throat, where is sucked up by the scavenge tube, but not before some leaks out thru the bushing. The cure for all this is to disassemble the carb, and clean it, and replace the float needle valve.
__________________
@(^.^)@ Ed 1977 Pearson P-323 "Dolce Vita" with rebuilt Atomic-4 |
#5
IP: 174.62.214.116
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Confirmed the functionality of choke
Thank you for the timely feedback.
We have confirmed the choke is performing as it should. So, I will turn my attention to the innards of the carb which does not have the mod for the adjustable main jet (far as I can tell). I have previously messed with the float so that might explain the cause for an abundance of fuel / over-rich mixture. Thanks again! |
#6
IP: 206.125.176.3
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have spares on hand
Vermonstah...if it has been a while since you removed the carb, be sure to have spare gaskets (flange & carb bowl) on hand. The carb bowl gasket is delicate, and the way the carb comes apart often damages it. I usually get pretty lucky with the flange gasket, and it stays intact, but I never count on the bowl gasket surviving a disassembly..additionally, my thought process is, if I am having troubles, why not replace it with a nice fresh gasket anyway?
Every time I prepare to place an MMI order, I go thru my spares and update my gasket inventory..I like to have two of everything that I might change in the field in my box...like all carb gaskets, water pump, impeller, etc. I like to carry one spare set of major things like head gaskets (2), valve cover, water jacket side plate, etc. This way, if I have a repair to make at the dock, I should be able to get the engine back up and running without waiting for parts, and can replenish my spare supply at me convenience.
__________________
-Shawn "Holiday" - '89 Alura 35 #109 "Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!) |
#7
IP: 208.251.135.189
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Order placed with MMI
Thanks Shawn for the advice to have good collection of spares on hand. In addition to the associated gaskets, I ordered a new float and float valve. I am not entirely confident that I can restore the existing carb to good working order, but if I can, it will become the jewel of my spares kit since I also ordered a new carb. Parts due late Thursday so I will update the thread with my progress.
Thanks again for the good counsel from throughout the forum. |
#8
IP: 206.125.176.3
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vermonstah..I was chasing what I thought was a chronic issue with my carb, so I ordered a new one last year too..turns out it was totally unrelated, but it is nice to have a shiny new carb and a good spare on hand. Taking the carb apart in the cockpit in the middle of an anchorage is not really my idea of fun.
__________________
-Shawn "Holiday" - '89 Alura 35 #109 "Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!) |
#9
IP: 75.67.155.224
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fouling plugs
We had the same problem with fouling plugs this season and for a week messed with the carb (which I had rebuilt last winter) to lean out the mixture for before finding that the points setting (should be .025) had slipped to .010. Weakened spark and inefficient combustion, it seems. Fixed!
Bill and Jeanne Tartan 34C #453 Otter |
#10
IP: 206.125.176.3
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Bill..good point. I had a '78 Civic and I had to periodically pull over and re-adjust the points as the set screw was stripping, and they would close up on me after prolonged highway runs. A streetlight usually worked well enough to do the job at night and get rolling again.
__________________
-Shawn "Holiday" - '89 Alura 35 #109 "Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!) |
#11
IP: 76.11.110.224
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EI...I always said either / or.
Electronic ignition, new coil and resistor is not a bad option. My spare engine sitting in the garage had EI on it and Dave Neptune talked me into installing it. Changed over the coil and external resistor on it as well and I've run the engine for 6 hrs straight at times without an issue. I didn't have an issue with the points and condenser, but the EI is still more efficient and trouble free. It took me about an hour to do the switch and that was taking if off in the garage, driving to the boat and installing it.
For those wondering if EI is a decent option?? Sure is, but also put a new coil and external resistor as well ...works perfect.
__________________
Mo "Odyssey" 1976 C&C 30 MKI The pessimist complains about the wind. The optimist expects it to change. The realist adjusts the sails. ...Sir William Arthur Ward. |
#12
IP: 70.27.58.162
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Quote:
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#13
IP: 129.83.31.2
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Clean plugs!
I am very pleased to report progress. Last weekend, I installed the new carb from MMI. And has been addressed many times on other threads in this forum, removing and replacing the carb is straightforward. So much so, even I can do it.... I knew right away that I had resolved the fuel leak, but I did not have the opportunity to get the engine up to temp for any period to test the plugs. We have had some steady winds at 20 knots this weekend, so I took her out today and made a point to motor the final 3 miles to the pin. And when I pulled the plugs, they were clean! All four of them! The photo might not do it justice, trust me, that is the cleanest plug I have ever removed from my engine. Note: I am running the Autolite 86 plug that MMI recommends as a slightly hotter plug. I have a new float and float valve for my previous carb, and I hope to get that back to decent working order so that it can serve as a reliable spare. As suggested, I also got the the Electronic Ignition from MMI. I have not yet installed it, as I wanted to deal with only one thing at a time. And now that it appears that I have the carb dialed in, then I will move on to the EI. I will be VERY happy to be done with points. Points are no big deal for many on this forum, but been too much for me.... Again, cannot thank the members of this forum enough. Don and Ken too - tops in my book. |
#14
IP: 12.219.49.130
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That is a nice looking plug. The picture shows it very well. Good job!
__________________
Mike |
#15
IP: 199.173.224.31
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I think you did the best thing. I have discovered that the carbs have a finite life span before cleaning them does not fix all their ills. A new carb from MM did wonders for my engine.
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#16
IP: 206.125.176.3
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+1 what joe said. A new carb answered a lot of questions and has made my engine runs heaps better too.
__________________
-Shawn "Holiday" - '89 Alura 35 #109 "Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!) |
#17
IP: 32.211.28.40
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Hey VT,
Jumping in here a little late, but I thought I'd ask a question - Are you using any oil? Having good compression doesn't mean that all the rings are good. The lower ring (oil control) seems to go first. You can still have good compression but be passing oil into the upper cylinders giving a dirty transom and fouled plugs. Just a thought.. |
#18
IP: 174.62.214.116
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Don't think I am burning oil...
Al - I don't think I am losing any oil past the rings. And to be more precise, I sure hope I am not, but I will pay closer attention for that. Compression has been good since I replaced the head gaskets, oil pressure appears good upon starting, idling and cruising. I will try to get a better sense of current oil level and pay particular attention when I dump the oil in a few weeks.
I will also let it idle for 30 minutes or more and then check the plugs and see how they look. The plugs looked great after cruising 45 minutes but I did not confirm that all is well at idle. If everything checks out, then I will move on to installing the electronic ignition. Thanks again to all! |
#19
IP: 129.83.31.1
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After idling, 2 plugs look great, 2 less so
So, I ran the test that I described above.
Upon starting the cold engine, I throttled down to idle (~800 RPM) and left it there idling for 30 minutes. Then, I pulled the plugs and checked them. Here is what I found: Plugs 3 and 4 look great, as in the picture above in Post #13. Plugs 1 and 2 are posted in order below. While not fouled, they don't look like they did after cruising 45 minutes last weekend. Some history: Last season, I spent chasing the cause of a #2 sticky intake valve. I had bad compression in #1 (35) and #2 (30) which led me to replace the faulty head gasket this past winter. Compression at the beginning of this season was #1 (90) and #2 (95), and admittedly I have not tested it since launch in May. Don suggested that the engine would continue to "heal itself" (my term, he likely said something more technical) and the sticky valve would self-correct as the engine ran at temperature this season. Well, I have probably not run at temp much this entire season with a properly functioning carb, probably less than 90 minutes total. So, I will put some more hours on the engine and then re-run my idle test and check for any residue on plugs #1 and #2. Question for the forum: should I add any MMO directly into cylinders #1 and #2? |
#20
IP: 199.87.177.179
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Lore from times past was it wasn't good on an engine to run at idle for long times because it "carboned up" and you had to run at full throttle periodically to blow the carbon out of it. So I would think what you found was normal. If you want to tune it further make sure your centrifugal weights under the distributor points plate are working properly, and perhaps lean the carburetor a touch, and make sure the timing is close.
Since you are worried about a stuck valve I would run another compression check and if the compression numbers look good, go sailing. Best, Jim
__________________
Jim Zeller 1982 Catalina 30 Kelleys Island, Ohio |
#21
IP: 161.213.49.150
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Quote:
To get into this a bit further........... There is a relationship between ignition, idle speed, and idle richness. That is to say for example if the ignition (dwell, timing, and advance) are not set to spec you will have to compensate with more idle speed and or more idle richness to even get the engine to idle. There is also a balance between idle speed and idle richness. The place to start is to get the ignition set to spec. Then balance idle speed against idle richness. You will eventually find the optimal setting for your paticular engine. Have fun. TRUE GRIT |
#22
IP: 129.83.31.1
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Not burning any oil
Least I don't think so anyway.
Lots of posts on the forum about fouling plugs, so I wanted to update my post here. At Winter lay up, I drained 3.7 quarts of oil from my engine. From what I can determine on the forum, that seems average or maybe even above average. No, I didn't record a precise measurement for oil added at last oil change, my log only says "approximately 4 quarts" which is not very helpful in this case. I will record a more precise measurement at Spring start up. I am ready to declare victory over my fouled plugs, which were the result of too rich mixture due to a faulty carb. There was fuel getting past the float rendering it almost impossible to regulate the mix. With too much fuel in the bowl, the bushing leaked. Time for a new carb. After replacing with a new MMI carb, and dialing in the mixture, the fouled plugs disappeared. And I am rebuilding that old carb this winter to add to my spares kit. I presume that with a properly functioning float, that should mitigate the leaky bushing long enough to get me to safe harbor in a pinch. Shortly after Spring launch, once the weather allows for some extended motoring, I plan to make the switch over to EI, per suggestions from John and Jim above to make sure the engine is dialed in just right. I need idiot proof and little to no-maintenance. Fewer opportunities for my mistakes. I have certainly been the beneficiary of an abundance of useful information from this forum, hope something in this thread is helpful to another. |
#23
IP: 71.118.13.238
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Your first plug looked like a rich idle and your second look confirms it. Your off idle colors look fine and NOT lean.
I would first try an additional 1/4 turn out on the idle screw to lean the idle a bit. If the beastie is a bit harder to start cold then your about right on the idle. Per John, check the dwell!!! I would also try a couple of more degrees of advance while at it. I had to idle my engine a few years ago in some really bad weather on my mooring. The harbormaster ordered all boats in the back row to keep their engines running until he could escort/pull them off. During this day I idled for 5 hours at 700. The next morning out of curiosity I checked the plugs and they looked absolutely clean and a light tan color. Anyone who says that an A-4 won't idle well just can't adjust it properly!!!! Dave Neptune |
#24
IP: 129.83.31.1
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Dave - thanks for the detailed feedback.
Always good to know that it is possible to get the engine dialed in just right, though I am not claiming that I can do it. But I am willing to try.... Question: since I will be installing the Moyer EI, what sequence should I follow to complete the fine tuning? Install the EI, then fine tune dwell, mix etc? Thanks again for helping me to break this down into manageable pieces. |
#25
IP: 71.118.13.238
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V, if it runs sort of OK, IE it starts and will idle I would not mess around further until I installed the EI. After the EI get the timing squared away. Do you have a timing lite or know how to use one? Marking where to start so after getting the EI installed you can start right back in the same spot. This will really help you out!!!
You can "set the mark" without the lite using the points! You will need a lite after that to get back to the mark though~~understand? Dave Neptune |
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