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pluto383
RO# 13487
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 Posted - Jul 25 2010 : 13:18:35
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My mercruiser 4.3L spluttered to a halt today and won't start. I have taken the spark plugs out one by one to check they were sparking and they all do. I then took the air filter off to look down the carb. Fuel is being squirtrd into the top of the carb when the trottle is openned fully and the engine is occasionally trying to start but then stops and it it only tries to start again after leaving it for a while, but the same thing happens. What is the next thing to check? I emptied the fuel filter. The fuel in the tank was put in about 3 months ago and it has been used only about 5 times, and then it was spluttering a bit at low revs. Could the carb be blocked up? Are there other injecting points other than the two holes at the top of the carb? I'm not sure but there could have been a small amount of salty water on a couple of the spark plugs, but it is a closed cooling system, so salt water could only have come up the exhaust. Any advise would be much appreciated. Thanks
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jtybt15
RO# 3300
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Posted - Jul 25 2010 : 15:04:15
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How old are the manifolds and risers? Is there steam coming from the exhaust?
Did it sputter when first start-up but run better after warm up? More details of past running prior to the problem.
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Charlie
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Homeport: Ca
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j-d
RO# 15782
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Posted - Jul 25 2010 : 15:06:34
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Please send more details about this 4.3 like Year, Drive, Hours, Carb, EFI. You say Carb, but the throttle body EFI gets called carb sometimes. When you crank it, does it sound like an engine with spark plugs in it being cranked (rhythmic sound) or like one without plugs (smooth sound)?
And you're right - Salt water can intrude from the riser or riser-to-manifold (or -to-spacer) joint. But not so much if it's a late model "dry joint" setup. Is it a "full" FWC system (fresh water through exhaust manifolds) or "half" (fresh water through block and intake only)? We need more info.
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God Bless, jd
1996 Sea Ray 215EC
Alpha One GEN II 5.7L/350CID/EFI/220HP
14-1/2*19 Stainless RWC
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Homeport: Sunny Florida
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pluto383
RO# 13487
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Posted - Jul 25 2010 : 15:58:15
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Hi, Thanks for the replies. The engine is a 2001 4.3L mercruiser. It is not an EFI, it has a Thunderbolt IV ignition system and I think it is a 2 barrel carburetor. It sounds normal when turning over (with spark plugs in). It has been taking a little longer to start this year but nothing excessive. It occasionally trys to carry on after ignition turned off (guessing that could be timing a bit out. It was trying to stall at low revs the past few times of using but again, only occasionally. It is a part closed cooling system. It has a heat exchanger which has the raw salt water coming up into it and out through the exhaust and fresh water running through the engine and the heat exchanger. That's why I don't think it's a gasket. If there was salt water, it must have come up over the riser of the exhaust. But not sure if this is the reason for it not starting. I'm wondering if it could be a blocked jet in the carb. Would this be the next test to take off the carb and clean it? It there an easier way to test the carb? I can only see the squirts of fuel coming out when the throttle if pushed fully forward, but is that the only way fuel exits the carb, or is there lower jets? It did splutter a little when started an got better when warm, it was fine planing, but after trolling at low revs for about half an hour, it spluttered a bit, I thought down on a cylinder and then spluttered to a stop. Thought it was a plug problem but checked them all one by one, by removing and holdong against an earth and turning over engine to check for a spark, which they all has, which is why I don't thing it's electrical. This is why I think it could be fuel. What next though? Thanks
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j-d
RO# 15782
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Posted - Jul 25 2010 : 20:20:02
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The fuel you can see squirt when you pump the throttle is from the accelerator pump in the carburetor. This at least means there's gas in the float bowl. The actual main and idle jets are farther in and down within the carburetor.
You say the plugs spark when you remove one and crank, right?
Remember to watch for fuel vapor in your bilge!
Do you get a fat spark from the cable feeding each/every sparkplug? If you weren't getting spark I'd suspect your kill switch.
I asked how it cranked, because if you can squirt fuel and each plug is sparking, then it seems to me that something jumped out of timing. You need fuel, spark, and compression. And things need to happen in synch.
Answer Charlie's questions and let's see what's next.
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God Bless, jd
1996 Sea Ray 215EC
Alpha One GEN II 5.7L/350CID/EFI/220HP
14-1/2*19 Stainless RWC
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Homeport: Sunny Florida
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jlee815
RO# 27501
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Posted - Jul 27 2010 : 15:29:00
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For what it is worth I had similar symptoms with a 1990 4.3 LX rochester 4 Barrel carbed 205 engine with thunderbolt ignition. Long story short I had the carbs rebuilt in 2009 and I still had starting issues after that. The mechanic blamed ethanol. If it sat for a while 15-20 minutes it would then start right up.... The carb rebuild was not an excellent one. Once I got it rebuilt a second time by someone who really knew what they were doing I have not had a starting problem since. I am not saying the carb is your problem but it seems like it could be. There is a Rochester carb rebuild video on this board somewhere but as experience indicated there are some things about those carbs that can just be learned via hands on experience over a lot of rebuilds.
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Jason
Doral Prestancia |
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Homeport: Lake Lanier GA
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pluto383
RO# 13487
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Posted - Jul 27 2010 : 15:36:22
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Really grateful for the help and advise, Thank you very much. I'm going to take out the carb tomorrow and dismantle and squirt everywhere with carb cleaner and clear the jets for peace of mind. If that doesn't help, compression test cylinders. Hope I'm working through this correctly, spark - then fuel - then compression.
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pdecat
RO# 842
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Posted - Jul 27 2010 : 15:43:09
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you have spark and fuel, at least you think it is fuel, so it should be firing or at least backfiring. The carb is not the problem since it sqiurts, it may not be perfect but the squirts should cause some firing. Since it isn’t firing unless the timing got really way off the fuel is bad. The most likely situation is that you have water. Hook up a separate fuel supply or even try filling the filter with clean gas.
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Bruce
legal disclaimer;
posts are amateur opinion only and should not be relied on as reasonable, safe, proper or in any way recommended.
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Homeport: Gulf Coast FL
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marathon man
RO# 23428
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Posted - Jul 27 2010 : 22:43:43
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Have you tried a well placed, safely thought out, shot of starter fluid, also with no fumes present. That will tell you a lot real quickly.
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Homeport: Ketchum, Grand Lake O' The Cherokees
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My mercruiser 4.3 won't start - help!
