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Its me again. After getting the wiring fixed the mower starts and runs better then it did when it was new. It has over 1150 hrs on it. Idles good, revs up good, doesn't back fire any more and runs super. I use it for several things and it is not unusual to run it 5 hrs a day. It was restarting when hot just fine. I thought all was well with this engine. All was good for 3 days & after about 15 hrs of running perfect it started being hard to start when hot again. I guess the DSAI modules are getting hot and not firing. Seems strange to me both modules would go out at the same time. They are OEM and suppose to last the life of the engine. Why would it not start on one cylinder? After the engine cools it starts fine. All the cooling fins are are clean. The whole engine is very clean. Is there any way I get more air to circulate where the modules are? Thanks for any help.

Cambre, I just replaced the modules on a Kohler 25hp about 3 weeks ago when it was doing the same thing. Wouldn't start hot. This engine had the single wire fixed timing modules but both were failing at the same time. I have seen the modules fail one at a time, but normally when one fails the other one isn't far behind.

ILENGINE said:

Cambre, I just replaced the modules on a Kohler 25hp about 3 weeks ago when it was doing the same thing. Wouldn't start hot. This engine had the single wire fixed timing modules but both were failing at the same time. I have seen the modules fail one at a time, but normally when one fails the other one isn't far behind.

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Thanks ILENGINE, I will buy new modules. Glad you explained why both quit at the same when hot. Thanks again.

Cambre, This kind of failure may be what is known as a lot failure. Another forum member is having a similar problem with a Jacks module for Troy Bilt. Lot failures are due to poor assembly , components, and lack of proper sampling by the mfgr. But most of all from lack of final electrical test at the factory. When a preselected quantity fails based on a sample of (for instance hundreds of) parts the entire lot must be scrapped. This is apparently not happening in many cases. IMO low price is an indication of this risk , for instance $15 vs $35-$50 for a module.

motoman said:

Cambre, This kind of failure may be what is known as a lot failure. Another forum member is having a similar problem with a Jacks module for Troy Bilt. Lot failures are due to poor assembly , components, and lack of proper sampling by the mfgr. But most of all from lack of final electrical test at the factory. When a preselected quantity fails based on a sample of (for instance hundreds of) parts the entire lot must be scrapped. This is apparently not happening in many cases. IMO low price is an indication of this risk , for instance $15 vs $35-$50 for a module.

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Thanks motoman, I'll make sure I get the best I can find. The Kohler parts list says $109 each. Seems high but I will get them.

I'm convinced I need new DSAI modules. I used the mower really hard today for 2+ hrs. I know it really got hot for a long time. I have been leveling some high spots on my 3 acre lawn. Some are large and there is plenty dirt to level out. I have a drag that farmers use to bust up dried cow patties in their pastures. This 26 hp Kohler handles it OK but I know it gets plenty hot. The thing is it just keeps running as long as I want. I parked it so I could do more grading with my backhoe bucket. I let the mower fast idle for over 5 minutes, then slow idle for 15 minutes. I always do this with a hot engine to let the cylinder wall cool while running so it doesn't warp. I killed it after that and tried to start it 30 minutes. Wouldn't start. Is there something in the module to keep it from starting but not stop it from running. Some times I use it for 2 or 3 hrs. then park it an let it idle for an hour some times until I need it again. After sitting for two hrs. it started. It only cranks half a turn and starts when its cool. I'm curious as to why it does this. It keeps running no matter how hot it gets, will run all day if I don't kill it. Thanks for answer.

It is the heat sink effect. As long as the engine is running the modules have cool air flowing across them. But when you shut it off, heat rises, and because of the blower housing traps the heat around the modules. what you describe is the exact same symptoms I experienced on a customer scag 25 hp with the fixed timing modules. It would run as long as you wanted, but if you shut if off for 2 minutes wouldn't restart until it cools. In this case would take about 20 minutes.

ILENGINE said:

It is the heat sink effect. As long as the engine is running the modules have cool air flowing across them. But when you shut it off, heat rises, and because of the blower housing traps the heat around the modules. what you describe is the exact same symptoms I experienced on a customer scag 25 hp with the fixed timing modules. It would run as long as you wanted, but if you shut if off for 2 minutes wouldn't restart until it cools. In this case would take about 20 minutes.

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Thanks ILENGINE, You answered and explained my question. Thanks

Cambre also an important heat sink is provided by the module base to seating metal . There is probably plenty of factory testing for "heat soak" after the fan is shut off , but seems like field conditions are always harsher than a test bed. As we mentioned before the little chips inside the modules have an upper limit which, if exceeded, will result in missing or failure to start. Some here have started collecting head and block temperatures so a person could flash a hand held temp gun and get a rough idea if overheat is truly present. Progress is slow.

motoman said:

Cambre also an important heat sink is provided by the module base to seating metal . There is probably plenty of factory testing for "heat soak" after the fan is shut off , but seems like field conditions are always harsher than a test bed. As we mentioned before the little chips inside the modules have an upper limit which, if exceeded, will result in missing or failure to start. Some here have started collecting head and block temperatures so a person could flash a hand held temp gun and get a rough idea if overheat is truly present. Progress is slow.

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Thanks motoman, I have been thinking about getting a temp gun. All your info is good and interesting. I am learning a lot from you, ILENGINE, bertsmobile1, reynoldston and others. Thanks.