520H dies in cold weather

[larryk1 1]

Hi

My 520H quits after running about 20 minutes in sub zero weather blowing snow. 

Acts like no fuel.

It will run on choke for a few seconds then wont start at all.

After setting for 10 minutes it re-starts fine. Then does it again and again.

Could it be carb icing or fuel pump freezing?

Any ideas are appreciated.

Tractor runs fine in weather down to zero degrees.

Thanks!

Larry in COLD northern Wisconsin

 

[Dieselcowboy 210]

Sounds like maybe you could try putting in a bottle of heat in the fuel tank. That would be the only difference if it runs good in warmer weather.

[rokon 64]

Larry, It could be a bad gas cap not venting properly causing the tank to go into a vacuum as fuel is drawn from it. Try loosening the cap and see how long it will run for. If that is not the problem, you will have to determine whether you are loosing fuel or spark to further diagnose the problem. I could be wrong, but after running for 20 minutes with the load of a blower on it even in subzero temps, I think the onan should be plenty warm enough that carb icing shouldn't be a concern.

[ericj 1,578]

onan's are known to have bad ignition modules not saying its your problem but don't rule it out till you at least check. the onan manual tells you how to check it. one way to check it would be to spray some carb cleaner into the carb and see if it will fire on that. good luck and let us know how you make out

 

 

eric j       

[dbartlett1958 96]

Larry, It could be a bad gas cap not venting properly causing the tank to go into a vacuum as fuel is drawn from it. Try loosening the cap and see how long it will run for. If that is not the problem, you will have to determine whether you are loosing fuel or spark to further diagnose the problem. I could be wrong, but after running for 20 minutes with the load of a blower on it even in subzero temps, I think the onan should be plenty warm enough that carb icing shouldn't be a concern.

Larry,

 

The suggestion Rokon made is worth checking out. The same thing happened to me a few weeks back with my 416. Fuel cap was the problem.

[varosd 1,185]

all of my newer gas caps are "well" vented!  all the of them have splits or are missing the clear cover.   if yours are the same way, maybe moisture from snow sitting on top of the cap seeping into the tank?

[leeave96 487]

Could be carb icing.  I would suspect a tad of water in the fuel line/tank freezing - perhaps clogging the fuel filter?

[thehorse 221]

I might think fuel also. I would drain what was in there and put in some fresh high octane with a little sea foam.

[larryk1 1]

Hi Everyone,

 

Thanks for all the input! 

Today I took a fuel sample, and it looked good. (no visible water)

I put some Iso-heet in the fuel anyway.

I checked the gas cap, and it is the newer Toro type with no clear lense, and it had no cracks. I also checked the vent. OK.

 

Then I blew snow for over an hour with no problems. (except me being froze and wet) ( I really need a cab for that thing!)

The temps today were 20 degrees warmer than when I had the issue. (15 above zero today) The problem never occurs unless it is below zero.

I did notice that when I was finished, the screen on the flywheel housing was really iced up. I then took off the air cleaner cover and found a small amount of ice, water, and snow in the air inlet tube that comes directly off the sheet metal over the flywheel.

I talked to a friend that told me that some of the older kohler twin cyl's you had to turn the air cleaner housing for winter use so that it would draw warmer air from around the exhaust area. He said some owners manuals actually had that printed in them.

I dont think that is possible on the Onan, but I was thinking of removing the tube between the fan housing and the air cleaner, so the carb isn't getting frigid air right off the flywheel just for winter.

Another friend told me to check the impulse hose on the fuel pump to see if it is collapsing etc. It looks good, but it also is in the fan housing exposed to the icy air flow.

 

It is supposed to be -18 tomorrow morning, so I will test it again, then report back to you all.

 

Thanks again for your help!

 

Larry

 

[P3x 56]

Could be too much snow blow back and entering the cooling louvers on the top of the hood and getting sucked into the air cleaner assy.  Has not happened to me before but saw a guy selling a 520H with a cover fitted over the hood louvers to prevent snow entry.  He did not state his reason but may apply to your problem.

 

Good luck.

[boovuc 1,090]

The KT Kohler engines do have the winter/summer air cleaner that you can spin to either take air off the manifold in the winter or not. This is something inherent to those engines and I have never seen it on an Onan. When you vacuum air into a small or narrow passage, it cools rapidly and on the KT engines, the intake manifold will actually get a coating of frost on it even at temperatures as high as 40F.

If your Onan is working well at temps of around 0 F, your intake air to the carb probably isn't an issue and isn't relevant to the Kohler design.

However, I would look at two things and one has already been mentioned.

The ignition module may still be the culprit. The other would be a small leak around the intake manifold. It wouldn't take much of a leak to cause the issues you discussed at temperatures that low.. As for moisture entering the air cleaner, ask yourself if the issues you had started during and after snow-blowing? If the backfiring and shutting down happened before you ever blew snow, then no. If it always does it during or afterwards, then maybe.

[larryk1 1]

Hello again everyone,

 

I ran the tractor for about 40 minutes yesterday at 10 below zero blowing snow. It ran perfect. I was driving up to my garage, and it started to spudder and slow down. Then as I was rushing to get it in the heated garage, it died.

I immediately took off the air cleaner and found no evidence of ice or snow anywhere. The fuel filter looked dry inside. By the time I got the hose off the oulet of the pump, it pumped fuel OK when I cranked it and it started up again when I reconnected the hose. I should have checked spark first when it died, but the way it slows down and sputters makes me think it was a fuel and not a spark issue?

Guess I will replace fuel hoses and/or pump, and ignition module if all else fails. By the way, I always use premium non-ethanol fuel in all my equipment, since I have seen the problems ethanol has created on the Outboards I repair at work.

I hope the cold weather goes away, but I need it a little bit more for testing this thing.

Thanks again to everybody, and I will report back what I find.

 

Larry

[cheesegrader 433]

Larry,

 

I have been working both my 520's this winter in temps of 10-15 below zero.

Not my idea of fun, but the snow dumps here get followed by bitter cold blasts.

I have not had any problems with air intake getting frozen during snowblowing,

and I can't imagine that drawing air from somewhere else is going to help.

The fuel pump and filter are exposed on the left side.

Could they be getting iced over with blowback snow?

Maybe just a weak and failing fuel pump?  Fuel line kinked by ice buildup?

Mine looks like a rolling Igloo when I get done, and I peel pounds of ice off as I work, though I have never come close to covering the flywheel screen.

[oaktown1987 82]

I don't know around there here in Illinois the premium even has ethanol in it star tron is a good additive to add to gas it's like heet on steroids it's cleans ur fuel system keep the ethanol from from seperating and and u can store ur gas up to two years with it

Sent from my iPhone using Tapatalk

[woodchuckfarmer 333]

Sounds like a wet coil and wires from all the snow your blowing

[Squawk 0]

Larry,  I had the same problem with the Onan in my 416-8 years ago.  Replacing the fuel pump did it for me.  If you catch it acting up again, try heating the fuel pump with a hair dryer to see if it makes a difference.

 

Squawk 

[larryk1 1]

Thanks again everyone,

I got it to act up yesterday, and it still had spark. It fired on ether too. I am going to order a fuel pump.

Thanks Squawk! Nice to know someone else had the issue too.

Larry

[ryno610 5]

My 416 did the same thing.  Would run fine and then die in the cold.  New fuel pump fixed it immediately, and no problems since.

Ryan

[lynnmor 7,301]

I found water in the fuel pump impulse hose that would freeze and stop the pumping.   After the engine stalls, latent engine heat would melt the ice and it would run for awhile till it did it all over again.  No real fix, just blow out the hose and change the engine oil to get rid of the moisture.

[larryk1 1]

Thanks Guys! Last winter was milder, and had no troubles, but am going to put in a new pump and impulse hose. I do change oil regularly, but I suppose moisture can occur since the machine is in a heated garage then used in freezing temps. The back and forth of temps may contribute to the issue?