rough idle/stall |
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Jllogan
Platinum Member Joined: May-18-2011 Location: canton, OH Status: Offline Points: 1728 |
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Posted: July-16-2012 at 11:20am |
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ok so Ive got nine hours on the boat since the engine went back in and it has been running great. Idleing perfectly, running strong no problems at all 100%. Towards the end of the day on saturday it very suddenly start idleing rough, it was loping barely hitting 500 rpm on the tach and when you put it in gear it would die. If you kept it revved over 1000 no problems and when you put it under power it stumble til you got it over 1000 and then just take off like a rocket, full power up through the band.
You could also tell it was really rich at an idle, mind you this was a sudden change as well, running perfect and then bam next time I slowed down I had this issue and it stayed that way all the way back to the trailer. Any ideas? Could the float be stuck open in the carb and dumping too much fuel in at an idle? |
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3337 |
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Certainly could, though 'stuck open' would be more dramatic, its more likely a peice of crud in one of the needle/seats overfilling the primary or secondary bowl. Could be either or both.
Another possibility, though remote, is the PV ruptured. You'll first need to make those visual observations with the SA off while its symptomatic. |
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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TheChad1976
Groupie Joined: October-12-2009 Location: Jacksonville FL Status: Offline Points: 44 |
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I am having the same exact problem. I have an 87 with the 351 in it, with the electronic ignition conversion. Engine has 112 hours and I can not get it to idle right to save my life. I've changed plugs, wires, fuel filter, cleaned the anti siphon valve, and even tried to adjust the carb. No Luck. I want to see what others say on here.
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Jllogan
Platinum Member Joined: May-18-2011 Location: canton, OH Status: Offline Points: 1728 |
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yes, you are correct it was a long day and I was tired so I just threw it in the garage and didnt bother looking down the carb yet. Just wanted to make sure I was barking up the right tree. I supposed I could recheck the points/gap but they are only 9 hours old. I feel like that would give me trouble all over though, not just at an idle.
Doubt the its the PV first it is also only 9 hours old. Also never backfired, ever, so dont see how it would rupture unless it was just a faulty one. I do have spares though so if I get really stumped I could try one. |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Chad,
Have you checked the timing? How about the mechanical advance? Even with the EI conversion, the advance is still mechanical. |
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Jllogan
Platinum Member Joined: May-18-2011 Location: canton, OH Status: Offline Points: 1728 |
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advance wouldn't affect the idle though. if its in time the advance wouldnt affect until revs were up.
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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It wil if the advance is hanging up and not returning all the way to base timing. |
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Jllogan
Platinum Member Joined: May-18-2011 Location: canton, OH Status: Offline Points: 1728 |
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yes but that would cause the timing to read advanced with the timing light. If your base timing is on mark +/- 10TDC then even if the weights were hung up it would still idle ok, it would just be all jacked up when you accelarated. Right?
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TheChad1976
Groupie Joined: October-12-2009 Location: Jacksonville FL Status: Offline Points: 44 |
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I have not checked the timing yet. I have never messed with timing before so I am "learning" ... Some of the symptoms mine is doing are:
*Rough Idle when under a load (in gear wants to shut off) *When you give it gas under load then it gives a chug chug and them jumps up and runs. *If I adjust the idle up to almost 1k it does ok but I don't like it idleing that high. *When I do get idle adjusted right, after I run it around the lake and back it doesn't stay that way (its either too hight again or too low when I come down off plane) *When idle is around 650 - 700ish then it wants to run rough |
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Jllogan
Platinum Member Joined: May-18-2011 Location: canton, OH Status: Offline Points: 1728 |
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ya, you need to check your timing. Thats your base line for your distributors advance curve. You need a timing light and it should be right around 10 degrees at 600 RPM. Rule out that first.
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Chad,
When the EI conversion was done, was the timing checked/adjusted? |
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watrski
Senior Member Joined: December-01-2010 Location: Chippewa Lake Status: Offline Points: 393 |
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I have a spare carb if you need.....
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Jllogan
Platinum Member Joined: May-18-2011 Location: canton, OH Status: Offline Points: 1728 |
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A good working one? Why do you have a spare? |
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TheChad1976
Groupie Joined: October-12-2009 Location: Jacksonville FL Status: Offline Points: 44 |
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I dont know the history of when the conversion was done. (I kind of whish it was still old skool points) The guy I bought it from had just installed a Jasper reman engine and put everything on when he did it. It had 25 hours on engine when when I got it I would assume he checked all of that but it was 3 years ago. It has 112 hours now.
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3337 |
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Chad I suspect you have a vacuum leak and/or the idle fuel orifices are boogared up in the metering block.
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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watrski
Senior Member Joined: December-01-2010 Location: Chippewa Lake Status: Offline Points: 393 |
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Last guy that borrowed it....worked fine for him. Spare? I guess so other people can borrow it...never needed it myself ;) |
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Bri892001
Grand Poobah Joined: September-27-2008 Location: Boston MA Status: Offline Points: 4947 |
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Justin,
One other remote possibility, but a quick easy check. I'm thinking one of your electric choke wires could have popped off, and the choke might have closed up on you. It doesn't make total sense, where you're running fine up top, but chokes are mechanically forced open at higher throttle. |
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Jllogan
Platinum Member Joined: May-18-2011 Location: canton, OH Status: Offline Points: 1728 |
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oh brian, nice thinking, ok Ill check that quickly as well, very easy to check and you are correct that would explain how it happened so quickly. also spring inside could have broken. |
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watrski
Senior Member Joined: December-01-2010 Location: Chippewa Lake Status: Offline Points: 393 |
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is your PCV hose port connected to anything? My local guru had me block it off.
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watrski
Senior Member Joined: December-01-2010 Location: Chippewa Lake Status: Offline Points: 393 |
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PS.... Let me take a pic of mine tonight to make sure I'm not getting the PCV confused with something else.
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Jllogan
Platinum Member Joined: May-18-2011 Location: canton, OH Status: Offline Points: 1728 |
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mine is a 25 year old carb didnt have those fancy pcv ports back then. Its goes into the spacer. Ill fiddle with it tonight if I have time and see if I cant spot something otherwise, I may just install your "spare" and then Ill know my issue.
Plus I need to come over and get some more evening chippewa skiing in, even on your "rough" water. I need a few days for my toe to heal though. |
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river ratt
Groupie Joined: July-22-2011 Location: ia Status: Offline Points: 61 |
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i'm having the same issue hard to start and keeping a consistant idle until its ran wide open/cruise for a bit . always having to adjust idle speed up at start then back down. my post was under chug. still not right i'm going to replace fuel pump so i can rule it out. plus a little sea foam . still falls on its face on a quick start
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dont slip on the glass
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Jllogan
Platinum Member Joined: May-18-2011 Location: canton, OH Status: Offline Points: 1728 |
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seafoam wont help. Are you sure your linkage is tight/adjusted properly? I also doubt its a fuel pump, if anything I would think it would idle ok but then fall on its face when it needed alot of fuel/wide open if the pump was weak.
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Jllogan
Platinum Member Joined: May-18-2011 Location: canton, OH Status: Offline Points: 1728 |
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also I didnt run it tonight but I did rule out the choke. It opened all the way when the element got hot, also the oil smelled a little like gas so that tells me something in the carb is letting too much fuel in again. Its frustrating that it worked great for nine hours, really thought I had it, wonder what changed/happened. I have rebuilt twice in the last year, maybe its time for a new one.
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SNobsessed
Grand Poobah Joined: October-21-2007 Location: IA Status: Offline Points: 7102 |
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I'm pretty sure that diagram is an automotive carb. If that is what you have, it would be best to get a marine one. |
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“Beer is proof that God loves us and wants us to be happy.”
Ben Franklin |
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Jllogan
Platinum Member Joined: May-18-2011 Location: canton, OH Status: Offline Points: 1728 |
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Yes I am 99% no one here has a auto carb, I think the diagram was just for illustration purposes. |
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3337 |
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I had the orig fuel pump slowly shred bits of red paper gasket into the carb fo.r two seasons before it failed
Caused lots of rebuilds inbetween. If you see red sediment in the bowl, jets or needles, that's what it is |
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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Jllogan
Platinum Member Joined: May-18-2011 Location: canton, OH Status: Offline Points: 1728 |
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Good advice, I dont know how old the pump is, I guess its possible that crap got in it. I have a little filer where the fuel line comes in so that should keep anything from getting through though. Its definitely getting too much fuel at an idle though, I can tell by how its acting and the smell.
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64stang
Newbie Joined: June-25-2012 Location: Wisconsin Status: Offline Points: 38 |
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Wow, was this timely. I have a 1990 351W PCM with a Holley carb. Last fall it started doing the exact same thing, very rough idle, running flooded would only idle good at 1200 rpm anything below caused loping and flooding, I could not adjust it out. So this spring I attempted to reset the timing with a cheap eBay light and could not get it right. Choke is functioning properly, I replaced plugs, wires, coil, points, condenser, and I also adjusted the air metering screws per instructions. With a new timing light I was able to make the point setup work very good. But when I had the timing issues I ordered a Pertronix Ignitor conversion so I went ahead and installed it. At first it started harder than the points and slightly flooded, otherwise it ran well, but now after maybe 20 hours I can not keep the idle set. At first start unless the idle is set high it will lope and stall, after a while it will be running at 1200 rpm, I then set the idle back and it runs fine for a while, then all of a sudden it will start idling very slow and loping, again I set it up. I am getting ready to reinstall the points. The Pertronix starts harder than the points for sure and I don't like that but I am not sure that the points will solve this. I am starting to think something is stuck or plugged in the Carburetor?
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SNobsessed
Grand Poobah Joined: October-21-2007 Location: IA Status: Offline Points: 7102 |
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Is it possible that one of the idle circuit passages is clogged in the metering block? Maybe it comes & goes with the throttle plate variation covering up the transition slots. I think you can buy the metering block as an individual part, if that is the problem.
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“Beer is proof that God loves us and wants us to be happy.”
Ben Franklin |
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