Lincoln Weldanpower Surge issue

G6 at Snook, TX

Well-known Member
I have a Lincoln Weldanpower from about 1987. It has a Briggs 16hp single cylinder motor on it and after about an hour of running, it begins to surge. We thought it a fuel issue, but that has been ruled out. It was switched from points to EI at some point. Would a failing EI cause a surge issue after about an hour of run time while under intermittent load? What other electrical things can we check? Would the ignition switch go bad in this manner?

Thanks
 
Just about anything that disrupts the engine performance can cause surging. The governor doesn't know why the engine slowed, it just wants to get it back up to speed, so it starts surging.

But, it almost always is a lean fuel condition. How did you determine it is not fuel? If any doubt, try a partial choke or give it a shot of gas with a pump oiler to see if that temporarily stops the surge.

Another test would be to remove the kill wire from the coil,(if magneto) see if that helps. Or if battery ignition, bypass the ignition switch. As for the electronic ignition, be sure all the connections are good. Anything is possible, but usually they work or they don't.

Of course, there is the obvious, replace the spark plug!
 
I have an idea, just a thought... Two things you said are clues, one being that you say it does this after about an hour of running, and secondly, with intermittent loads.

I would bet a dollar with you that I know exactly what the problem is, it is carburetor icing.

Take your wife's hair dryer and blow some hot air into the air inlet, you may have to remove the air cleaner to do this, and within about 20 seconds, it will cough a little, miss a little, then clear right up and run fine as long as you hold the hair dryer there.

The coughing and missing is caused by the ice melting and drops of water running through.

Been there and done this, the ice building up is interfering with the movement of your throttle plate.

Marlin
 
To answer the questions: We have eliminated the gas issue due to the fact that the flow to the carburetor is good, and considering how hard it runs when welding, the lack of fuel would manifest much sooner than one hour in. When it goes to surging, it is always at about an hour.

To test the ignition switch--it is an electric starter--would you just jumper the wires with alligator clips?

Secondly, tell me how this machine would ice up? I live in Texas and it was 72* today. I am not saying that it can't, but considering the climate and the machine, I don't understand the icing issue.
 
In this motor, the Briggs manual calls for either a resistor (802592) or a standard (492167) plug, which is the preferable plug? The manual doesn't give guidance on that matter. Plugs are cheap, I will replace it since it is several years old.
 
Your engine can be considered to be idling, if under no load, even if it is running at 2,000 RPM. You said it happens after running, maybe an hour at intermittent loads.

Those are the two clues. It takes a while for the ice to build up, and the intermittent loads means that it is spending a lot of time running with the throttle plate almost completely closed, meaning that you are running with a high intake manifold vacuum.

I had the exact same problem with a generator running at 1,800 RPM, it would run just fine under a large load when the throttle plate was more open and intake manifold vacuum was low.

You can have severe carburetor icing at 90 degrees or even higher, if you are running a high enough intake manifold vacuum. And guess what, the relative humidity is not all that important either.

Ask a small airplane pilot about carburetor icing and have them tell you at what temperatures it can occur, you will be surprised.

I just found this quote on this web site:

http://www.boldmethod.com/learn-to-fly/aircraft-systems/dont-let-carb-ice-happen-to-you/


"The temperature range where carb ice can occur is equally surprising. According to the FAA, carb ice is possible from 10F to over 100F, with serious icing possible from 20F to over 90F (-7C to 32C)."





There would be absolutely no cost to you to give the hair dryer test a try, you have nothing to lose. I personally know of two cases of generators being fixed of this problem when the owners fashioned a sheet metal "stove" around the exhaust manifold/muffler on their small engine, one being my generator, and the other being a portable welder where the owner was angry enough to throw his welder away.

I was there, and used my wife's hairdryer on his welder, I wish you could have been there and seen the expression on his face when it smoothed out and ran like new.

He had tried "everything".

And, like others have said, this may not be your problem, your mileage may vary, and so on.

Marlin
 
I agree. When fully warmed up it could be going lean. A loose carb or intake tube at the head could be one issue. Plugged fuel cap vent could be another. When it starts to loose speed, the governor opens and the carb runs on the high power circuit. I would check the carb connections to the engine, The cap, and then remove the sediment bowl and clean the tiny ports that feed fuel into the main jet tube. Jim
 
I have seen carbs ice up at 105 here in Texas.Could be your problem. I would also look for intake leaks and maybe some gas cleaner in the fuel.
 
Like you said, what have I to lose with the hairdryer? If I have a vacuum leak, where are some good online options to purchase parts for this age of machine?
 
As to this issue, I replaced the governor springs--a cheap replacement considering the age. Then I enriched the carburetor. After an hour of run time, I burned through about six rods at 150. No problems. But I did notice the area around the carb/manifold connection was sweating quite a bit.

It welded like a scalded dog, but is there anything to worry about with that sweat? My 8n Fords do that from time to time, but normally it is nothing to worry with.

Humid today. Rained this morning. Sunny this afternoon with drying-- if that matters.
 

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