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I have an old JD 317hp lawn tractor. It has a newer(11years old) Kohlor 18hp engine in it. I have had no problems until this summer when i noticed the engine a little hard to start. During the hot summer months the engine has been acting up. After the tractor has been working with the grass cutter for 25-30 minutes the engine starts to surge much like it would if it were running out of fuel. It will get progressively worse until it stalls out. I have changed plugs, fuel and air filter, and nothing seems to be working. It appears to act up when you load it up. Could this be a govenor issue?

Hey there - WELCOME to LMF!

I moved your thread to the Small Engine & Mower Repair Forum. :smile:

Could be a fuel pump failing after it gets hot. Saw it once on a briggs or maybe something is causing a vapor lock situation from heat around the carb.

Thanks alot for your input. I will investigate.

When the tractor is running, can you feel if there is any hot exhaust venting around the carb? Where does the muffler connect to the block in relation to the carb? Just wondering if a new manifold gasket was used when the engine swap was done??

Doesn't appear to be any heat around the carb however it does appear to be a lot warmer around the engine when i lift the engine hood. I have had the tractor with the new engine for about 10 years and never really had any significant engine problems thus far. I now can't even get it to keep running. It will start but i need to choke it to keep it running and than of course it appears to get too much fuel and stalls out. What ever it is it has progressed from being just an intermittent problem to a biggy.

sounds like vapor lock....check the fuel pump.....what is the engine model?....can you take pictures of it in the tractor?

Check the line that runs from the block up to the fuel pump very carefully for cracks or blockage. IIRC, those can be a little temperamental.:wink:

Update; i have been on vacation the last few weeks and to my suprise the self healing option on my tractor doesn't work! Thanks for everyone' assistance. Right now i am looking at fuel pump or ignition module based on input from others. A friend of mine checked the carb settings and it started much better. I hoped that would be it but as the engine got warm i got through half of my 66'X125' lawn and it started acting up again. Last night i couldn't even get it to stay running. I have to choke it full to keep it running and after about 20 seconds it dies because it is being choked too much! I will attempt to attach pictures of the engine nameplate. Still scratching my head.

that engine is definitely a vapor lock candidate with the carb right on top of the heat maker....i would definitely check the fuel pump for low output

Is the remedy basically a replacement fuel pump? Could you explain the vapour lock to me or steps to confirm vapour lock? I am pretty sure the fuel pump is nylon? Is the vapour lock a symtom of normal wear? Appreciate the help.

vapor lock is when gasoline goes from liquid to gaseous state...it can happen in the fuel pump or fuel lines or carb....or all of them...its caused by heat and when fuel gets air in it ..it exacerbates the problem...if the fuel pump is weak...it could allow the heat to get to it or if the air is getting in at the pump...check for cracked fuel lines and the fuel pump:smile: ........ http://www.kohlerengines.com/onlinecatalog/pdf/tp_2204_b.pdf ....... take a look at this manual

also ..of course check the fuel
filter..it is also a suspect culprit

When i first started having problems i replaced the fuel filter, changed plugs, air filter and replaced tank with fresh fuel. The engine definitely appears to be having a fuel issue because there is plenty of crank when starting and the plugs are firing. I have noticed that it turns over quite a bit before it actually fires and starts but as i said now it doesn't even want to keep running so i imagine the problem is getting worse. I am currently shopping on line for a fuel pump. Any suggestions? I am up in Canada near Michigan's UP.

theres lots of JD online parts places....but i would pull the fuel line from the carb [ while the engines cold] and crank to see if fuel is getting to it first...... GreenPartStore - Parts for John Deere Lawn Tractors, John Deere Lawn & Garden Tractors, John Deere Mowers, John Deere Attachments, John Deere Accessories .... JD Mower Parts .... and EBAY too

I changed the fuel pump last night after first checking the lines and trying the old pump while cranking the engine. It did appear to be hit and miss as far as pumping the fuel althoug i am not sure how well they are supposed to pump. I made sure the lever was above the camshaft when i reinstalled and i tried the engine. It would turn over but not start so i assumed that there was an air lock and raised the back end of the tractor so gravity would move the fuel to the pump. It worked. the engine started and seem to run fine so i left it running for about 15minutes mid throttle with PTO engaged. I worked the lawn for a while and things seemed ok but than the engine started surging again! The big difference this time was that it did not go ahead and stall out on me but i didn';t push things either. It appears the problem is persisting but seems to have improved somewhat. Could it be something to do wiht the govenor i wonder? I guess it may be time to have someone look at it.

From the symptoms you describe, my first approach would be to make certain that fuel supply is addequate. Since you have verified this, I would then suspect the carburetor. Since you apparently have a rubber hose delivering fuel to your carburetor, if vapor lock is the problem, it would most lkely be from engine overheating.
As with any "air cooled engine" perodic cleaning of the cooling system cylinder heads fins and related parts would be recommended.
I would suggest cleanining the engine and clean the carburetor.:thumbsup:
I think that you will find the carburetor to be your problem. If it has been recently cleaned---clean it again and be thorough with cleaning of every small passageway.
Even the smallest amount of water, or trash, can cause problems. :thumbdown:

Thanks for your advice. I certainly notice significant debris around the fin area while i was changing the fuel pump. The symtom certainly seems to appear as the engine gets hot and loaded up. This summer cutting grass really caused problems, to the point it would just surge and sputter so bad that it would stall out. In the early summer i found the engine hard to start so i cleaned the plugs and filters and used a carberator cleanning product. I followed the instructions carefully but i wonder if it didn't just loosen some debris up only to move it around somewhat. I was leary about taking the carb out and cleaning it because i have tried in the past on snowblowers only to find that the unit wouldn't operate any better. Most people including me don't like touching the carb. I even used an ultrasonic cleaning machine at work and it did an excellent job. I follow instructions well but lack the skill of the fine tuning and tinkering needed i think for carb work.

i have to agree with Giles:thumbsup:

Last carberator i cleaned i used the ultrasonic cleaner at work with i believe just warm soapy water? Any advice?

Carburetors are really very simple, at least after you have worked with hundreds:laughing:
Even the most "unskilled" person can accomplish cleaning with the right patience, obsurvance, and tools.
I have cleaned many carburetors by disassembly, applying spray carb. cleaner and many did not require replacement gaskets or other parts.
In most cases, compressed air is necessary to blow out ALL SMALL PASSAGEWAYS. Some passageways are about the size of a single wire of a wire brush or the smallest cutting torch tip cleaner.
It is advised to thorougly clean the outside surface of the carb. before removal. I usually use spray carb. cleaner, and pay attention to the holes used for linkage cable and governor rod hookup.
As far as adjustment goes--gently turn adjustment screw in, until slightly seated, while counting the turns. This is done before removal of the adjustment screw and if the adjustment has not been altered, this setting should be very close.
Many people can have a good running machine and suddenly have a problem and their first thought is to adjust the carburetor.
I differ from a lot of people:laughing: in that I do not believe perodic carburetor adjustment is necessary. You are simply "masking" a problem.
I have equipment that is more then 30 years old with many carb cleanings, and the adjustments are the same as when the machine was new.

Thanks for the help. I feel encouraged!

My 12 HP Kohler in my 12-50 Jacobsen ran the same way until I got a donor need valve for the high speed air/fuel mix . The original one was slightly bent . I did not see it until the part rolled on the steel tractor lift . If i had not noticed it i was going to start checking the intake exhaust valve clearance.
Starts everyday now .