Backfiring Engine when under increased load

[Mower Man 9]

I took the attached pictures of the spark plug and then I tried to start it up after 5 hrs of cooling down.  This is two views of the same spark plug.

 

 It was very hard to start and it backfired a few times both thru the exhaust and thru the carburetor/air cleaner.  Finally I got it started and then drove it to the gravel and I drained the 89 octane Chevron Gas with Techron out of the tank.  

 

Then i put in 3/4 of a can of Sea Foam and started it up.  Several times it would bellow black smoke and quit and then I would restart it and let run for 10 min.  Then I parked it and will refill the tank with auto gas and then try to restart it tomorrow.

 

It is strange that it backfires and dies and then finally restarts and runs for enough time to do all the mowing.    I wish it would just run smoothly like it did last year.

 There are only 298 hours on this 1998 WheelHorse Tractor.  That is only 14 hrs a year.

 

 

[gwest_ca-(File Mod) 11,102]

Sounds like it is a model 73448 with a Command CH14 engine.

Garry

[Mower Man 9]

2 hours ago, gwest_ca said:

Sounds like it is a model 73448 with a Command CH14 engine.

Garry

Exactly.  Do you know why it backfires some of the time and behaves normally the rest?

 

[gwest_ca-(File Mod) 11,102]

Usually a backfire is the result of a lean condition or not enough fuel.

 

A loss of spark can cause it also as that can leave extra fuel in the engine and if the spark returns it may result is a backfire. This model had this problem and there was a kit to correct it.

Download the 2 pages.

I don't know how it works on this model but usually the seat switch allows the engine to run if the operator is in the seat and the pto is ON. Operator falls out of seat - the seat switch grounds the ignition and the engine quits. The Command engine is like a magneto ignition and is self powered. The ignition wire is simply grounded to stop the engine which on this model is accomplished by kill relays.

 

Garry

 

I posted the wrong link - corrected now.

[6bg6ga 272]

I'll go back to the "lets go back to the basics" comment as ineffective and irrelevant.  These are not high performance engines and don't have vacuum advance and timing control. I still believe its simply a lean condition and will go down that route first because its the less costly route to go and it makes sense to treat it this way first. The plug looks from what I can see of it as a normal plug not wet or sooty. Light tan in color from what I see meaning slightly lean in my mind.

 

However, having said this if it doesn't respond to treatment it could vary well be a result of the ignition/ electronic type coil having a problem. This problem WILL ALSO manifest itself the SAME EXACT way.  Malfunctioning ignition of this type can fire incorrectly, can function perfectly, and then go bad again.  The starting problem or lack of needs to be looked at. I would dump a little gas down the carb when it didn't start to see if it did fire then.

 

Also, is this equipped with an electronic shut off valve? If so is it supplying the gas or partially opening up.....also a cause.     If it has a solenoid gas control valve I would remove it temporarily and see if the condition improves.

Edited May 3, 2017 by 6bg6ga

[Jake Kuhn 1,556]

Just went through this exact problem on a 12 horse kohler last week. First tried spark plug, condensor, coil, and a fuel filter and it finally turned out to have a very small pinhole in the float. 

[6bg6ga 272]

I seriously doubt this is a safety switch problem. Instead of throwing parts at it I would simply make a bypass and install that. I'm not a fan of replacing parts unless one can prove the part is actually at fault. A bypass will either prove or disprove this. Save your money until you find the problem.

9 minutes ago, Jake Kuhn said:

Just went through this exact problem on a 12 horse kohler last week. First tried spark plug, condensor, coil, and a fuel filter and it finally turned out to have a very small pinhole in the float. 

 

That doesn't sound quite right to me. A pin hole in the float would cause the float to sink in the chamber which would cause the fuel level to go up which would make it run rich not lean. With a pin hole in the float the float lowers which causes the needle to move off the seat which allows more gas in and generally causes a rich condition NOT a lean one.

Edited May 3, 2017 by 6bg6ga

[gwest_ca-(File Mod) 11,102]

This wiring diagram may be easier to understand but it is not listed for 1998. I suspect the change in the above service bulletin makes this 1999 wiring appropriate for 1998.

Garry

[rmaynard 15,610]

23 minutes ago, 6bg6ga said:

I'll go back to the "lets go back to the basics" comment as ineffective and irrelevant. 

 

It's not irrelevant to want to know what model tractors he has, and what engine is on it.  Not all problems boil down to a "one size fits all" fix.

[6bg6ga 272]

Actually I will disagree. Its still probably a basic lean run condition. People need to learn how to see this instead of trying to group problems based on what type of engine it is. At 7 years old I was helping the old man install points and condenser and set dwell check timing on the family car. Back then in the 50's there wasn't electronic ignition or computer control. One had to learn to diagnose problems based ONLY on what was happening. This is the only LOGICAL way to teach anyone proper diagnostic skills. So, like I said I will disagree because nothing is to be gained by simply saying hmmm that's a Kohler and as a Kohler is ONLY has these problems. Trying to group something in this manner will end up biting you in the butt.

[rmaynard 15,610]

The mere fact that you asked this question "... is this equipped with an electronic shut off valve?" requires someone to know what the model is and what engine is on it.

[gwest_ca-(File Mod) 11,102]

9 hours ago, gwest_ca said:

Sounds like it is a model 73448 with a Command CH14 engine.

Garry

 

7 hours ago, Mower Man said:

Exactly.  Do you know why it backfires some of the time and behaves normally the rest?

 

Garry

[6bg6ga 272]

No, sir my logic in figuring out possibilities makes me question a number of things. Having played with the little engines I am aware that some are so equipped. My attempt is still to make others so they will also look and think.

[6bg6ga 272]

11 minutes ago, rmaynard said:

The mere fact that you asked this question "... is this equipped with an electronic shut off valve?" requires someone to know what the model is and what engine is on it.

 

Let me pose a question... do we for fact actually know the engine in this tractor is in fact the original? Could it be from another model? Could it be a dealer replacement? As such would it necessarily have the same safety switches, fuel shutoff, or even ignition, carb? I can keep going on this.  Unfortunately, we can't be there to check and observe the engine. We can only go with what we know based on the information received. The ideas I get from good forums is they in effect make the thread starter think, look, and learn. People like you and me enjoy the challenge of trying to solve these problems. Posing questions to them like "does it have a fuel solenoid" make the person look, and actually see something instead of relying 100% on someone else to solve the problem completely.

 

If you still feel my methods and ideas are incorrect please do let me know and I will gladly back out of this forum. 

[rmaynard 15,610]

2 minutes ago, 6bg6ga said:

No, sir my logic in figuring out possibilities makes me question a number of things. Having played with the little engines I am aware that some are so equipped. My attempt is still to make others so they will also look and think.

 

Some of our members here are collectors, others are restorers, many are tinkerers, there are loads of mechanics with collectively 1000's of hours of experience working on small engines, and there are just as many who don't have any idea which end of a screwdriver is the business end. We are all Wheel Horse lovers. For that reason we as a group will try our best to help anyone with a problem. Therefore, knowing what we are dealing with is the first key to finding the solution. Of the 15,000 members out there, one may just have the same model with the same engine who has had the same problem. 

 

That is why I asked the question. 

[Racinbob 11,236]

Well said Bob. I’ve lost count of the number of times somebody has contacted me and starts in telling me what’s happening and what he has already tried and I end up starting out my end of the conversation by saying “whoa! Back the truck up. What are we working on?” Troubleshooting 101, step 1, what are you working on? That goes for any field of work.

We kinda got sidetracked here. Now that we know what motor we are talking about my thoughts go to the CH15 I have. I’ve never had the issue with it but I’m thinking about the little quirks that are different from the K-series, B&S, etc. Unfortunately I can’t add anything constructive to what already has been suggested. I think @Mower Man has some good information that will eventually lead him to the problem.

[Mower Man 9]

4 hours ago, gwest_ca said:

Usually a backfire is the result of a lean condition or not enough fuel.

 

A loss of spark can cause it also as that can leave extra fuel in the engine and if the spark returns it may result is a backfire. This model had this problem and there was a kit to correct it.

Download the 2 pages.

I don't know how it works on this model but usually the seat switch allows the engine to run if the operator is in the seat and the pto is ON. Operator falls out of seat - the seat switch grounds the ignition and the engine quits. The Command engine is like a magneto ignition and is self powered. The ignition wire is simply grounded to stop the engine which on this model is accomplished by kill relays.

 

Garry

 

I posted the wrong link - corrected now.

I disconnected that seat sensor when I first bought the Garden tractor in 1998.  It has worked fine since then

I have never rebuilt a carburetor.  Maybe I should just buy a new one and install it?  I should find the model number and order one.  

I have not started it up today yet.

[Mower Man 9]

It started right up this morning.  I will see how it mows next week after the grass grows.  

 

[illinilefttackle 399]

I must admit- I'm at a loss at the attitude expressed ib this post. Everyone in this Forum belongs to it because they enjoy this Hobby & the association with others that feel the same. No matter how much experience someone has in a field- you can always learn more, another way, etc. Closing your mind to learning something new is tragic. This-  like most problems with these machines will turn out to be a simple fix- some thing over-looked, etc. Help is here, respect & humility are the keys to obtain it. Now I will get down off my soap box- Good Luck!- Al

[6bg6ga 272]

9 hours ago, Mower Man said:

 

 

Im done  I'm out  Prease remove me from the list.

[Mower Man 9]

Thank you all for your thoughts.  I will post again after I have some grass to mow.

[Mower Man 9]

Since

On 5/3/2017 at 2:44 AM, gwest_ca said:

Usually a backfire is the result of a lean condition or not enough fuel.

 

A loss of spark can cause it also as that can leave extra fuel in the engine and if the spark returns it may result is a backfire. This model had this problem and there was a kit to correct it.

Download the 2 pages.

I don't know how it works on this model but usually the seat switch allows the engine to run if the operator is in the seat and the pto is ON. Operator falls out of seat - the seat switch grounds the ignition and the engine quits. The Command engine is like a magneto ignition and is self powered. The ignition wire is simply grounded to stop the engine which on this model is accomplished by kill relays.

 

Garry

 

I posted the wrong link - corrected now.

I checked my Seat Switch and discovered that I had shorted it out with a staple and taped it with electrical tape probably in 1998.  Well,  The tape was partially worn and would short out on certain bumps and sometimes kill the engine.  

I attached a picture of my non Wheelhorse approved modification.

So...

    I shorted the two wires together with a wire splice and the engine ran great.

The Lawn grew and I mowed it.  The mower did not back fire until I ran it out of fuel..  Do you think that I fixed it?

Would that cause intermittent back firing if that switch was partially, intermittently shorted to ground by touching the

Wheelhorse metal under the seat above the gas tank?

 

Time will tell.   

[953 nut 55,856]

On 5/3/2017 at 5:44 AM, gwest_ca said:

Usually a backfire is the result of a lean condition or not enough fuel.

 

A loss of spark can cause it also as that can leave extra fuel in the engine and if the spark returns it may result is a backfire. This model had this problem and there was a kit to correct it.

Download the 2 pages.

I don't know how it works on this model but usually the seat switch allows the engine to run if the operator is in the seat and the pto is ON. Operator falls out of seat - the seat switch grounds the ignition and the engine quits. The Command engine is like a magneto ignition and is self powered. The ignition wire is simply grounded to stop the engine which on this model is accomplished by kill relays.

 

Garry

 

I posted the wrong link - corrected now.

 

 

11 minutes ago, Mower Man said:

think that I fixed it

You sure did!           Looks like Garry was right again!          I think you will want to replace the switch to be safe.

 

 

 

 

[6bg6ga 272]

To me and I'm sure I'm probably alone in my thinking but I'm not ruling out the possibility that you had both seat switch and carb problems. Unfortunately we aren't there to check things personally and the only thing anyone can do is give their best guess based on the information from the thread starter and common sense. The main thing is your running.

[Mower Man 9]

On 5/10/2017 at 3:22 AM, 6bg6ga said:

To me and I'm sure I'm probably alone in my thinking but I'm not ruling out the possibility that you had both seat switch and carb problems. Unfortunately we aren't there to check things personally and the only thing anyone can do is give their best guess based on the information from the thread starter and common sense. The main thing is your running.

I ran another tank of gas thru it and it only backfired and quit once.   If it does it more then rebuilding the carburetor is the next step.  I will have to find the model number and order the rebuild kit.