I've been lurking on here for a couple years now and have learned a lot from you guys, but after many searches, I haven't been able to find a situation like mine.

I have owned this motor for about three years now, and I have the same recurring problem: my motor loses power under load (a lot of missing and sputtering, even dies on me) when I give it anything more than idle throttle. However, the interesting part is that this only happens in the morning when the temperature is lower than about 60 degrees. Basically, it stalls and sputters on the way to my duck blind when it is cold and damp, but on the way back to the launch I have absolutely no issues--it runs at about 3200 rpms just like it's supposed to (from what I have heard/read).

I have read that it might be a fuel pump issue--I've changed it and no difference. Carb/jets--had it cleaned by a mechanic twice--and it's been better for maybe one use and then gone back to the same old. Bad gas--I ran all the gas out of the motor, bought a new tank, and put new gas in the new tank, with no change in performance. I've also tried using no primer bulb and/or putting the fuel line straight into the tank without the quick connect, and nothing changes.

I can't see how this motor can run perfectly fine after midmorning, but have so much trouble when it's a little cold outside. If anyone has a suggestion, I'd love to hear it because I'm at the point of just replacing the engine. Thanks in advance

Well it sounds like you've ruled out fuel problems. Have you ever pulled a plug on one side to see if the motor keeps running, to see if it's running on both cylinders when it does it?

You also mentioned DAMP. This sounds like it could be an ignition problem, moisture tends to mess with sensitive electrical stuff that's reaching the end of it's life, as does cold. That's why people have more battery problems in the winter.

I forgot to add that--i did pull both plugs and when i pulled one of them, there was no difference in the amount of sputtering, so basically, that one wasn't firing. I have this little tester that you can hook in line between the boot and spark plug and it lights up when electricity is sent to the plug. I did this last year, but i want to say that it was getting a spark but not actually firing. I also forgot to mention that I changed the plugs with no change in problems. However, if the electrical components are the problem, what would i need to change?

You might wanna take that one to a good small engine mechanic or lawn tractor place, so they can diagnose it without you having to buy parts until it's fixed. I'm no mechanic, but I would try my plugs, plug wires and coils first, in that order.

If you are getting spark all the way to the plug, it may be a compression issue on that cylinder.
(stuck valve, Burnt valve, valve not seating properly, head gasket or the likes.)

When the motor is running cold pull each plug wire separately and see what changes.
Do it when it is warmed up too.

I thought about compression issues with that cylinder, but wouldn't a compression problem happen all the time, not just the cold mornings?

Yeah, thats the only thing that is stumping me.

Id guess at a bad coil or spark plug boot grounding our

I sprayed clear silicon on my spark plugs wire and mine doesnt do it anymore.

one of your wires prob just has a nick in it to where it is groundin out .......i would check wires

I am reluctant to mention carb ice as you mentioned 60F. morning temps but that is what I would expect if it was 45F or cooler. When you have high humidity and cool temps it can be a problem. Any way to warm the air before it goes into the air intake? Sounds like your ruling out other stuff. Good luck. Duckdon

thanks for the replies so far. Is it correct that if my spark plug wire is grounding out or my coil is bad, my spark indicator tool that hooks between the plug and boot should not light up?

Duckdon, I have not ruled out air intake issues like you suggested. I am not sure that temperature is the problem because the motor will run later in the day even when temps are in the 30's or 40's after having issues in the early morning. I do think humidity is some part of the problem. Another thing i noticed today is that the air filter smelled like gas, which doesnt seem right.

So when I have the problems again, I am going to try to remove it and see what happens, in addition to pulling both plugs and using the spark tester to see which cylinder is the problem, and try to troubleshoot from there. In the meantime, any other suggestions are welcome.

Have you tried the silicone spray??

no, i haven't gotten a chance to get any and quite honestly don't really know what it is. Do you have a recommendation of what brand to get? Thanks, hopefully that will be an easy fix

i'm almost certain it's electrical, and probably your kill switch circuitry. The cool temps are causing metal to shrink (contract) and short out. Corrosion is the likely culprit.

Had this exact problem with a 20 lt. It would explain your problem and still getting spark.

Tracing it is gonna be fun, try bypassing temporarily and see if it fixes the problem.

Ya dont think your getting carb icing do you?

indawoods, i will look at bypassing the kill switch today when i get home.

Gee, carb icing sort of makes sense as far as the symptoms go, but i've changed the fuel, gas tank, had carb cleaned, etc, and the problem is still there. There are tons of people running the same kind of motor as me in the same conditions and don't have this problem--so what would make mine ice and theirs not? That being said, i don't want to rule anything out at this point, so how can i tell if the carb is icing, and what is the remedy?

Thanks for the continued help

I have a 16 vanguard gdlt that would stall out when the temps got below 40. My fuel pump would quit working, why i dont know but it got worse as it got colder. as soon as i would pump the bulb is would quit sputtering and get right back up for 30 sec or so then i would have to pump the bulb again. i replaced the pump and all the fuel lines but we are locked up here with ice so i wont know till next year if prob is solved but it was a fuel prob for me. i had no hose clamp on the fuel lines where they connected to the pump and i suspect they were sucking air when it got cold not allowing the pump to work like it should?

I am on the way to hunt right now, hopefully I will have the problem so that I can troubleshoot. I will post what happens later. Thanks for the help guys.

my problem is definitely electrical. I used the spark tester thing while having problems yesterday morning and every time the engine sputtered, the light on my tester did not light up--meaning no electricity was getting to the plug. I will check the kill switch wire to that cylinder and the voltage to the coils to try and isolate the problem, and i'll probably try to just bypass the kill switch temporarily and see if it works the next time

does both cylinders do that in the morning... I had a time figuring out why mine was cutting out... found out it was the inline fuse holder, might want to check that too

well i found what looks to be at least part of the problem. When testing the voltage to the coil, I noticed the coil on the side that was having the problem arcing to some metal it was mounted on. So i sealed that up with some silicon and I will try it tomorrow to see if it's fixed.

I'd put money on it, saying that fixing that arc will be the end of your problems.

Just wanted to let y'all know that I tried the motor out this morning nd it worked like a champ. Thanks for the help

Good deal thanks for the feedback

simple fix good luck brotha