# Vapor lock on Scotts S1642 mower?



## billymac (Apr 16, 2009)

I have a Scotts S1642 riding mower with a Kohler engine that has recently developed a problem...

It stalls out while mowing with symptoms of fuel starvation. After sitting for a minute, it will start back up and run for a short time (1 - 2 minutes), then it happens again. If I let it cool down for some time (30 minutes to an hour or so), it will then run fine, for enough time to finish mowing.

It appears the combination which sets it off is:
1. Engine has been running over an hour.
2. Gas tank is less than half full (maybe only because of #1 - I don't know if it is part of the problem)
3. Mower has either made a quick turn or run along a grade.

Other observations: There is a transparent fuel filter. When the engine dies, the filter seems to be empty. Sometimes, it looks like there are bubbles coming into the filter from the carburetor direction. Normally, the filter looks to be about half full or more.

No part of the fuel line lies at a higher plane than the fuel outlet from the tank, but a sharp turn or grade could maybe cause it to allow air into the lines.

Does this sound like vapor lock? How could I fix this? Why would this start happening after 8 years on a mower that otherwise runs OK?

Thanks for any advice.


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## geogrubb (Jul 28, 2006)

Try running it with the fuel cap off or loose, the cap may not be venting properly. Have a good one. Geo


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## 30yearTech (Sep 14, 2006)

The fuel cap would be the most obvious culprit as geo pointed out, but if you have replaced the fuel filter recently, it could be the problem. Certain types of fuel filters do not work well on Kohler engines, particularly the gravity feed units.


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## billymac (Apr 16, 2009)

I did have a problem with a clogged gas cap vent a couple of years ago with similar symptoms, but I checked that this time and removing the gas cap does not relieve the problem like it did before.

I changed the fuel filter, but probably more than three years ago. I will try a new fuel filter, OEM if I can find it.

Thanks.


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## justin3 (Apr 10, 2007)

Yes you need an oem Kohler filter, I have had problems when using Briggs or generic filters on Kohler motors.


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## billymac (Apr 16, 2009)

Arrghh!

I installed a new Kohler fuel filter, and now the problem is worse.

I know it doesn't depend on fuel level in the tank as I once suspected, because it started misbehaving within 15 minutes today with the tank almost completely full.

It appears to be related to sudden movements (bumps, hard turns, etc).

Typical scenario:
1. Running fine
2. Make a hard turn or hit a bump (of which there are many)
3. A few moments later, engine starts to sputter. No fuel visible in fuel filter. If I fiddle with the choke - sometimes I can keep it running to avoid having to restart, other times it just dies.
4. Fuel refills the filter after just a minute or so, and I restart the engine if I was unable to keep it going.
5. Everything is fine until #1 happens again.

Any suggestions? Other than this aggravating problem, the mower runs fine.


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## RKDOC (Jun 20, 2006)

Check for something floating in the gas tank. Sounds like it is plugging the outlet. Then when it dies it floats away, only to return and plug the outlet.
Good luck


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## 30yearTech (Sep 14, 2006)

There may be a problem with the float needle and seat or the float, where it's not letting fuel into the carburetor fast enough. You may want to shut the fuel supply off to the carburetor and remove the float bowl and have a look inside to see if you can better tell how these components are working.


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## billymac (Apr 16, 2009)

More information.

At the time I posted the last update, I was about halfway through my 2 acres.

When I went back out, it was really awful - I could not go back and forth one time across my yard with out the [email protected]%# thing quitting on me. I thought about the vapor lock angle a bit more and how it is a heat related problem. I took off the engine cover. No more stalling the rest of the way. woo - hoo!!!

I don't think this was a coincidence, because I could make the problem happen at will with the cover on and could not make it happen with the cover off.

I suppose I could cut a hole in the cover, and install a naca duct with a blower 
Or I could just cut the grass with the cover off.

It seems like it fits the M.O. of vapor lock. Why would this start happening more or less all of a sudden on 10 year old mower? Any ideas on how to fix this short of mowing with the cover off?

thanks for all your responses so far.


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## J Man (Mar 9, 2010)

hey billymac - 
did you ever get your issue resolved. I have a S1642 and i am experiencing the same exact type of issues.


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## J Man (Mar 9, 2010)

*vapor issue on S1642*

did you ever get your issue fixed (was it really the engine cover). I have a S1642 and i am experiencing the exact same issue.


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## PJ07901 (Oct 24, 2010)

*Vapor Lock Issues*



J Man said:


> did you ever get your issue fixed (was it really the engine cover). I have a S1642 and i am experiencing the exact same issue.


I have experienced the exact same issues as described here and I believe it is vapor lock. I removed my fuel line just before the filter and gas only trickled out and then actually stopped (I had more than 1/2 tank of fuel). I then heard a loud bubble type noise as a bubble went up the line into the tank and then gas was coming out again and when I loosened the gas cap a full flow of fuel came out. To try and remedy the situation I pushed a paper clip into the little vent hole on the top of the tank opposite the gas cap and I pulled the gaskets out of the inside of the cap and put them back to see if possibly they were stuck. The problem seems to be solved and I also have gotten into the habit of loosening the gas cap periodically if I'm running for long periods and starting and stopping to unload grass/leaves.
Does anyone think a new gas cap would be a good idea? It doesn't look like it vents but I assume it does allow air to pass. I love my mower by the way. That Kohler engine still runs great after 8 years!:thumbsup:


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## 30yearTech (Sep 14, 2006)

PJ07901 said:


> I have experienced the exact same issues as described here and I believe it is vapor lock. I removed my fuel line just before the filter and gas only trickled out and then actually stopped (I had more than 1/2 tank of fuel). I then heard a loud bubble type noise as a bubble went up the line into the tank and then gas was coming out again and when I loosened the gas cap a full flow of fuel came out. To try and remedy the situation I pushed a paper clip into the little vent hole on the top of the tank opposite the gas cap and I pulled the gaskets out of the inside of the cap and put them back to see if possibly they were stuck. The problem seems to be solved and I also have gotten into the habit of loosening the gas cap periodically if I'm running for long periods and starting and stopping to unload grass/leaves.
> Does anyone think a new gas cap would be a good idea? It doesn't look like it vents but I assume it does allow air to pass. I love my mower by the way. That Kohler engine still runs great after 8 years!:thumbsup:


The fuel tank must be vented for fuel to flow. Almost all tanks vent through the fuel cap. Some caps have baffles and check valves in them to prevent fuel from flowing back up through the vent. Many can be taken apart for cleaning and some cannot. If you suspect you cap is not venting properly and it cannot be cleaned, then a new cap is the logical way to go. They are not overly expensive usually around $7.00 to $10.00 for a new one.

Best of Luck... :thumbsup:


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## phishears (Nov 26, 2010)

Ok, my turn. I've got the same problem. Scott's riding lawnmower, made by John Deere, 1642 Kohler engine.

I've replaced the filter, the gas cap, and I'm still experiencing the problem. I have a clear fuel filter and when I start its full of gas and then it goes dry. 

I guess I need to start looking at the float assembly someone mentioned earlier.

I bought this unit in 1999 and it's been excellent until now.

Help!


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## geogrubb (Jul 28, 2006)

phishears said:


> Ok, my turn. I've got the same problem. Scott's riding lawnmower, made by John Deere, 1642 Kohler engine.
> 
> I've replaced the filter, the gas cap, and I'm still experiencing the problem. I have a clear fuel filter and when I start its full of gas and then it goes dry.
> 
> ...


If the fuel filter runs dry the problem is between the tank and the filter not the float assembly. Remove the fuel line from the tank side of the filter to see that you have a good flow to the filter, you may have a crimped or collapsed fuel line. Have a good one. Geo


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## 30yearTech (Sep 14, 2006)

In addition to what geo stated, you also need to make sure you have the proper type of fuel filter. There are different filters used for engines that have a fuel pump vs a gravity feed setup. The wrong fuel filter can also cause this issue.


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## phishears (Nov 26, 2010)

Thanks Geo. Yesterday I replaced the fuel line from the tank to the filter and from the filter to the engine. She ran great for 30 minutes and then it dried up again. The guys at the Deere parts dept. suggested the fuel pump. I guess it can't hurt but this is really getting frustrating.


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## phishears (Nov 26, 2010)

geogrubb said:


> If the fuel filter runs dry the problem is between the tank and the filter not the float assembly. Remove the fuel line from the tank side of the filter to see that you have a good flow to the filter, you may have a crimped or collapsed fuel line. Have a good one. Geo


Yesterday I replaced the fuel line between tank and filter and filter and engine. She ran great for 30 minutes and then the same thing, started choking and the filter was going dry. While I had the tank out I made sure the outlet was clear.

The guys at the Deere parts dept. suggested the fuel pump. Couldn't hurt, but this problem is gettting old!


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## phishears (Nov 26, 2010)

30yearTech said:


> In addition to what geo stated, you also need to make sure you have the proper type of fuel filter. There are different filters used for engines that have a fuel pump vs a gravity feed setup. The wrong fuel filter can also cause this issue.


Thanks the folks at Deere gave me a clear filter that you can see the filter in, its made in Israel. My previous filter looked more like a flying saucer, you couldn't see the filter.

I'm going to try a different filter before I change out the fuel pump.

Thx


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## jsouth (Jan 31, 2008)

Does your mower have a fuel pump.Type in donyboy73 on utube and watch is today video on a vacuum hose,going to the fuel pump to the valve cover.Hope this helps.

Jerry


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## Whiter (Nov 16, 2000)

I had the same mower with the same problem and I determined that it was a plugged fuel cap. I went through the whole fuel not coming thru the filter to the point where I removed the filter altogether when finally a friend told me about the gas cap. The mower worked really good until the battery exploded and I finally got rid of the tractor.

Good Luck

Whiter


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## edward spens (Aug 5, 2007)

I had the fuel line one that it would close up when it would not get gas


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