What causes sneezing, low rpm misfiring, and won't idle?

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  What causes sneezing, low rpm misfiring, and won't idle?

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Author Topic:   What causes sneezing, low rpm misfiring, and won't idle?

pcrussell50 posted 04-13-2012 02:32 AM ET (US)
This is an Evinrude v4 crossflow in great visual shape that came with one of my old boats, (not a Whaler). I decided to try to use it today after rebuilding the carbs in October and only idling it on the muffs. It has an ordinary choke, not that newer quick start enrichment solenoid. It runs GREAT, at higher rpm if i can get it there without dying, but I can barely keep it running at 1500rpm--where it has an irregular miss, and occasional sneezing. I rebuilt the carbs, including changing the core plugs, fairly recently. I did a compression test this afternoon and got:
128-134
125-128
as viewed from behind. I have not done a leak down test.
I'm seeking some guidance as to where to start my troubleshooting. I "feel" like it's a fuel problem, or an air leak or broken reed. I don't "feel" like it's electrical, unless the base timing is way off--but "feelings" aren't worth squat in a deterministic mechanical system.
I'm tempted to tear into the carbs again just to make sure--unless someone here advises me otherwise. I've come to love carburetors for marine applications, but my real expertise is in fuel injection.
-peter
contender posted 04-13-2012 07:57 AM ET (US)
Peter, Hate to say it but I feel you have a problem with one of your carbs, low idle jet clogged? Partial blockage? it is something simple, but unfortunately I think you will have to go through the carbs again...
KDW posted 04-13-2012 10:10 AM ET (US)
Assuming it wasn't running that way before the carb rebuild?
Sounds to me like its running mainly on 3 out of 4 cylinders. Maybe one of your new core plugs is leaking air? Or, maybe one carb. float/needle is sticking closed.
Might try and see if you pull the spark plug wire off one cylinder at a time to determine which carb. seems to be the culprit....obviousely, the one that seems to make no difference.
KDW posted 04-13-2012 10:13 AM ET (US)
Forget the float issue. Forgot it runs well above low idle.
Could also be trash around a low idle jet and/or are the jets set correctly.
KW
pcrussell50 posted 04-13-2012 01:21 PM ET (US)
Thanks, guys. Off go the carbs again. Last time I didn't give them a "proper" cleaning. I tricked myself into thinking I didn't need to. Lesson learned.
It's nice to have the guidance to chase down more promising leads instead of having to face the whole gamut of possibilities.
-Peter
Binkster posted 04-13-2012 01:48 PM ET (US)
Peter, Wow, when I read the title to your thread, I thought you might be having a heart attack. Thankfully its only outboard trouble.
rich
contender posted 04-13-2012 02:06 PM ET (US)
Peter, do them one at a time and take your time, go through the entire carb, the smallest blockage will cause a problem, And if you purchase the kit use all of the new stuff/parts, even the ball bearing. Carbs are simple but can be finicky...good luck to you
PS I like using OMC grease on the gaskets and setting the carb, makes a nice seal that you can get apart, do not use the grease inside the carb just on the gaskets....
pcrussell50 posted 04-13-2012 09:07 PM ET (US)
Great idea on the greased gaskets, Rich! I like it. I may try that trick on some of my car engine builds. Not much out there more time consuming and irritating than scraping gaskets. That's one thing I like about more modern engine design--O-ring sealing. No paper gaskets = no scraping.
-Peter
Mr T posted 04-14-2012 10:43 AM ET (US)
My crossflow is a cold blooded beast as well. When it starts doing the same thing, it's time for a seafoam treatment for me. Seems to make a big difference, and it's cheap and easy.
pcrussell50 posted 04-14-2012 06:25 PM ET (US)
I hate to waste people's time on idle speculation, there's a little more. I've exchanged one problem for another. See the reason I rebuilt the carbs the first time is that I could not open the throttle without killing out the motor. It idled fine at the time, but wouldn't go full throttle. Now it goes like a scalded cat, but won't idle... So back when it wouldn't go full throttle, off went the carbs for a rebuild, and I found that one of the four main jets was outright missing--not even present where it should be--empty hole where the jet goes. (Remember), I have more motors than boats, and this motor essentially came as a "freebie", (it's actually very, very good shape), with a boat. Otherwise, the carbs looked pristine on the inside. Nevertheless, I did the whole thing, including r'n'r'ing the core plugs--whereupon I gouged one pretty badly at the outer edge of the bore, where it may no longer be a good seal. But I pinched my nose, crossed my fingers, and forged ahead--an action that resulted in an epic FAIL. According to some crossflow gurus on another forum, mine are the exact symptoms of a leaky core plug--as well as clogged idle jets.
So we shall see...
On an interesting note, the "fix", according to Evinrude guru Al Stoker, is to seal it with some hard-drying varnish made for petroleum products, called Gasoil. It's used as a pipe sealant for commercial gasoline-oil-propane-LPG piping and hosing. I've been studying it, and it's some pretty neat stuff--very specialized, though. I'm surprised that in all my years as a "gear head", I hadn't heard of it. Al says that authorized BRP repair shops have it.
-Peter
thegage posted 04-14-2012 08:04 PM ET (US)
I'm rebuilding the carbs on my '92 Johnson 90 V4, and the Seloc manual mentions the use of Gasoil for the plugs you mention. I can't seem to find a source for it, however, and my local shop doesn't know about it.
John K.
thegage posted 04-14-2012 08:08 PM ET (US)
Actually, it may be Gasoila (with an "a"):
http://www.gasoila.com
pcrussell50 posted 04-14-2012 09:33 PM ET (US)
You're right on the spelling. My bad. I'm closing in a source of it. If I find it first, I can send you a capful, (more than you'll need). I'll let you know.
-Peter
thegage posted 04-15-2012 03:29 PM ET (US)
My guess is that their E-Seal product is the one to use since it's formulated for gasoline with ethanol.
John K.
thegage posted 04-16-2012 04:01 PM ET (US)
I actually found some at a plumbing supply store near me.
I popped out the old plugs and found there was no sealant on them. I suspect the carbs were rebuilt at least once, and whoever did it wasn't too thorough. Maybe that was the cause of my mir-range stumble and rough running?
But now I've got a separate problem. The float bowls on the carbs on this boat are plastic, and both are warped; now I know why it seemed like fuel was slowly leaking from somewhere into the lower cover: because it was. Why there weren't additional screws designed on the bowl I'll never know, but it looks like OMC was eventually aware of the problem because replacement bowls are aluminum.
John K.
pcrussell50 posted 04-28-2012 04:07 AM ET (US)
EPILOGUE:
Rebuilt the carbs yesterday, installed them today. Problem solved. Runs great now.
FWIW, instead of sealing the core plugs with Gasoila, I sealed them with finger nail polish--as recommended by Al Stoker, (renowned OMC guru), as an alternative to Gasoila.
-Peter
thegage posted 04-28-2012 10:37 AM ET (US)
Glad it worked out for you.
I have my replacement bowls, but they require new mid-range jets which no one stocks, so I'm still waiting for them to ship.
John K.
KDW posted 05-01-2012 07:53 AM ET (US)
Hey Peter!!
What color finger nail polish???..pink or purple?
Bet those carbs sure look pretty now!
Feel it's my obligation to jab anyone using women's make-up products on such a manly job! Maybe calling it by the chemical name may protect you from such attacks in the future. :)
Kenny

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Author	Topic: What causes sneezing, low rpm misfiring, and won't idle?
pcrussell50	posted 04-13-2012 02:32 AM ET (US) This is an Evinrude v4 crossflow in great visual shape that came with one of my old boats, (not a Whaler). I decided to try to use it today after rebuilding the carbs in October and only idling it on the muffs. It has an ordinary choke, not that newer quick start enrichment solenoid. It runs GREAT, at higher rpm if i can get it there without dying, but I can barely keep it running at 1500rpm--where it has an irregular miss, and occasional sneezing. I rebuilt the carbs, including changing the core plugs, fairly recently. I did a compression test this afternoon and got: 128-134 125-128 as viewed from behind. I have not done a leak down test. I'm seeking some guidance as to where to start my troubleshooting. I "feel" like it's a fuel problem, or an air leak or broken reed. I don't "feel" like it's electrical, unless the base timing is way off--but "feelings" aren't worth squat in a deterministic mechanical system. I'm tempted to tear into the carbs again just to make sure--unless someone here advises me otherwise. I've come to love carburetors for marine applications, but my real expertise is in fuel injection. -peter
contender	posted 04-13-2012 07:57 AM ET (US) Peter, Hate to say it but I feel you have a problem with one of your carbs, low idle jet clogged? Partial blockage? it is something simple, but unfortunately I think you will have to go through the carbs again...
KDW	posted 04-13-2012 10:10 AM ET (US) Assuming it wasn't running that way before the carb rebuild? Sounds to me like its running mainly on 3 out of 4 cylinders. Maybe one of your new core plugs is leaking air? Or, maybe one carb. float/needle is sticking closed. Might try and see if you pull the spark plug wire off one cylinder at a time to determine which carb. seems to be the culprit....obviousely, the one that seems to make no difference.
KDW	posted 04-13-2012 10:13 AM ET (US) Forget the float issue. Forgot it runs well above low idle. Could also be trash around a low idle jet and/or are the jets set correctly. KW
pcrussell50	posted 04-13-2012 01:21 PM ET (US) Thanks, guys. Off go the carbs again. Last time I didn't give them a "proper" cleaning. I tricked myself into thinking I didn't need to. Lesson learned. It's nice to have the guidance to chase down more promising leads instead of having to face the whole gamut of possibilities. -Peter
Binkster	posted 04-13-2012 01:48 PM ET (US) Peter, Wow, when I read the title to your thread, I thought you might be having a heart attack. Thankfully its only outboard trouble. rich
contender	posted 04-13-2012 02:06 PM ET (US) Peter, do them one at a time and take your time, go through the entire carb, the smallest blockage will cause a problem, And if you purchase the kit use all of the new stuff/parts, even the ball bearing. Carbs are simple but can be finicky...good luck to you PS I like using OMC grease on the gaskets and setting the carb, makes a nice seal that you can get apart, do not use the grease inside the carb just on the gaskets....
pcrussell50	posted 04-13-2012 09:07 PM ET (US) Great idea on the greased gaskets, Rich! I like it. I may try that trick on some of my car engine builds. Not much out there more time consuming and irritating than scraping gaskets. That's one thing I like about more modern engine design--O-ring sealing. No paper gaskets = no scraping. -Peter
Mr T	posted 04-14-2012 10:43 AM ET (US) My crossflow is a cold blooded beast as well. When it starts doing the same thing, it's time for a seafoam treatment for me. Seems to make a big difference, and it's cheap and easy.
pcrussell50	posted 04-14-2012 06:25 PM ET (US) I hate to waste people's time on idle speculation, there's a little more. I've exchanged one problem for another. See the reason I rebuilt the carbs the first time is that I could not open the throttle without killing out the motor. It idled fine at the time, but wouldn't go full throttle. Now it goes like a scalded cat, but won't idle... So back when it wouldn't go full throttle, off went the carbs for a rebuild, and I found that one of the four main jets was outright missing--not even present where it should be--empty hole where the jet goes. (Remember), I have more motors than boats, and this motor essentially came as a "freebie", (it's actually very, very good shape), with a boat. Otherwise, the carbs looked pristine on the inside. Nevertheless, I did the whole thing, including r'n'r'ing the core plugs--whereupon I gouged one pretty badly at the outer edge of the bore, where it may no longer be a good seal. But I pinched my nose, crossed my fingers, and forged ahead--an action that resulted in an epic FAIL. According to some crossflow gurus on another forum, mine are the exact symptoms of a leaky core plug--as well as clogged idle jets. So we shall see... On an interesting note, the "fix", according to Evinrude guru Al Stoker, is to seal it with some hard-drying varnish made for petroleum products, called Gasoil. It's used as a pipe sealant for commercial gasoline-oil-propane-LPG piping and hosing. I've been studying it, and it's some pretty neat stuff--very specialized, though. I'm surprised that in all my years as a "gear head", I hadn't heard of it. Al says that authorized BRP repair shops have it. -Peter
thegage	posted 04-14-2012 08:04 PM ET (US) I'm rebuilding the carbs on my '92 Johnson 90 V4, and the Seloc manual mentions the use of Gasoil for the plugs you mention. I can't seem to find a source for it, however, and my local shop doesn't know about it. John K.
thegage	posted 04-14-2012 08:08 PM ET (US) Actually, it may be Gasoila (with an "a"): http://www.gasoila.com
pcrussell50	posted 04-14-2012 09:33 PM ET (US) You're right on the spelling. My bad. I'm closing in a source of it. If I find it first, I can send you a capful, (more than you'll need). I'll let you know. -Peter
thegage	posted 04-15-2012 03:29 PM ET (US) My guess is that their E-Seal product is the one to use since it's formulated for gasoline with ethanol. John K.
thegage	posted 04-16-2012 04:01 PM ET (US) I actually found some at a plumbing supply store near me. I popped out the old plugs and found there was no sealant on them. I suspect the carbs were rebuilt at least once, and whoever did it wasn't too thorough. Maybe that was the cause of my mir-range stumble and rough running? But now I've got a separate problem. The float bowls on the carbs on this boat are plastic, and both are warped; now I know why it seemed like fuel was slowly leaking from somewhere into the lower cover: because it was. Why there weren't additional screws designed on the bowl I'll never know, but it looks like OMC was eventually aware of the problem because replacement bowls are aluminum. John K.
pcrussell50	posted 04-28-2012 04:07 AM ET (US) EPILOGUE: Rebuilt the carbs yesterday, installed them today. Problem solved. Runs great now. FWIW, instead of sealing the core plugs with Gasoila, I sealed them with finger nail polish--as recommended by Al Stoker, (renowned OMC guru), as an alternative to Gasoila. -Peter
thegage	posted 04-28-2012 10:37 AM ET (US) Glad it worked out for you. I have my replacement bowls, but they require new mid-range jets which no one stocks, so I'm still waiting for them to ship. John K.
KDW	posted 05-01-2012 07:53 AM ET (US) Hey Peter!! What color finger nail polish???..pink or purple? Bet those carbs sure look pretty now! Feel it's my obligation to jab anyone using women's make-up products on such a manly job! Maybe calling it by the chemical name may protect you from such attacks in the future. :) Kenny