Fixing a Surging or Pulsing Generator in Cold Weather

I wish I knew more about engines, large and small.  I like to believe that I know a bit more than average, but that’s probably not saying much.  I suspect that most people treat their cars and other internal combustion devices as “black boxes” in which gas (and occasionally oil) go in, and then they go now.

In any case, homesteading has slowly ramped up my store of tips and tricks and knowledge, even if part of me wishes it wasn’t necessary.

In the past I have had a bit of trouble with my old generator beginning to surge or pulse while charging the batteries.  At first I had chalked it up to something not being properly adjusted, and so I turned the only screw I could find – the idle adjust.  This didn’t have much of a noticeable effect, period, so I ended up taking it to KC Automotive to see if they could find anything wrong with it, which of course, they couldn’t.

This problem seemed to come and go randomly, so I let it slide, and currently that generator has given up, there seems to be a problem with the fuel line, and as I have a second generator, I haven’t been really motivated to try to fix it.  I also really don’t want to take it back to get it looked at again, as it has been in the shop many times in the past year and I think perhaps it too just needs to be replaced.

The new generator is smaller and has some quirks of its own (surprising how quickly a kW of charging and then a kW of fridge compressor can both add up to 2kW, which plays havoc with a 1.5kW maximum surge rated machine).  But it so far has been rather reliable.

Lately though it too has begun surging.  At first I thought it was perhaps an interplay between the generator charging, and the charge controller, as I noticed it mainly when the sun began to shine on the solar panels.  As such, I would usually shut off the generator anyway because that indicated that I was getting enough power from the sun.

Then it changed, and even when the charge controller was disconnected the generator still insisted on pulsing.  I didn’t like this development.  I didn’t like this at all!

So, I started with the few things I could do easily.  I removed the air filter to see if perhaps something was amiss there.  I was a bit surprised to find it nearly frozen in place.  Further investigation revealed that there was a small tube from the cylinder head going into the air filter compartment, and it had frost all around it, blocking it out.

I had no idea what this tube was, or its purpose, but I cleaned off the ice, cleaned it out, and replaced everything.  The generator ran about an hour or so and I was tickled before it began surging again.

Asking Google for answers was unsatisfying, but instructive.  It seems this tube is a breather to release pressure on the top of the cylinder head.  It’s somewhat important, as an ongoing blockage puts quite a bit of stress on the cylinder and lubrication system.  Annoyingly though, few people reported this issue except in page after page of warnings about aeroplane engines.

The consensus was that there is usually lots of moisture blown out of that tube, and in extreme cold, it condenses and freezes until there is a blockage.

I tried running the generator with the air filter completely removed to see if that would stop trapping the moisture (in winter, it seems that air filters aren’t quite as important because there are far fewer particulates in the environment).  This really helped me to confirm this issue because once it began to surge again, I was able to see actual chunks of ice being burped out of the breather tube.

I began to think perhaps I had to wrap a small “hot pocket” type thing around the breather tube, or keep spraying some sort of water displacer into it or adding it to my fuel.  I was headed to town to purchase those items when I decided to stop in at KC Automotive and ask K! for his opinion.

As always, it was a really rewarding errand.  K! had encountered this issue before already and immediately suggested insulating the breather pipe as a solution.  He was thinking of regular pipe insulation, when I realized that I still had some scrap pieces of closed cell insulation laying about in the yurts.

I ran my other errands in town, picked up Donna and Kenny from Willow Springs, and returned home.  Although my trip to town is always draining, it was overcast and I wanted to try to pump up the batteries a bit more.

I used my knife and a drill bit to form a shell for the breather, and realized that it wouldn’t be possible to insert the breather into the air filter with the insulation in place.  Luckily I had purchased a wrench set JUST for the generator and left it there, and it fit the bill for removing the whole air filter assembly.  This made it much easier to align the tube and replace the air filter assembly with my new “winterized” breather tube in place.

Air filter assembly completely removed.

Note the latex gloves.  Not nice in sub zero temperatures, but better than gas and oil all over your hands.

I even replaced the actual foam filter inside and put the cover back on, to make this a fully fair test.

Also careful that no little bits of foam were hanging around inside the air filter.

All done!

The foam insulation interfered slightly with the choke arm, but it quickly aquired a gouge where the lever pressed into it, and I was able to start up the engine with a few pulls.

Inside I unplugged the fridge and adjusted the inverter/charger to ensure a good charge without issues, and the generator ran great for about three hours.  I’m not sure if it began to pulse towards the end.  The charger showed a fluctuation of between 7 and 10 amps, but I really didn’t hear anything that would normally bother me in the sounds from the genny.  I shut it off anyway though as it was getting late and I didn’t want to have to go out to shut it off in my pj’s.

One factor that tempers my enthusiasm though is that it was warmer than it’s been for a long time – only 9 degrees below zero.  I will have to try it out again when we get back closer to -20 and see what happens then.

In the meantime, I am giving this “generator hack” a pass.  I will try to report back after it has had some more extensive testing.

1 thought on “Fixing a Surging or Pulsing Generator in Cold Weather”

  1. Hey Steve

    Funny when you talk about planes having the same issues! When I was in SSM one cold morning we had two planes lose all their oil from a blown seal and both had to make emergancy landings. One landed on Vermillion lake near sudbury. They both had their oil breather tubes (which where insulated)

    glad you found a solution


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