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JohnF2015
JohnF2015, Small Engine Technician
Category: Small Engine
Satisfied Customers: 1079
Experience:  Owner/Service Technician at S & J Small Engines
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I have a kohler 15 hp that backfires and stalls in 20-45 mins

Customer Question

i have a kohler 15 hp that backfires and stalls in 20-45 mins then let sit 2-5 mins starts again äll over
Submitted: 1 year ago.
Category: Small Engine
Customer: replied 1 year ago.
do you know what the valve gap is?
Customer: replied 1 year ago.
you said already had an answer now I've been waiting hrs now? i'm not happy with this place
Expert:  gofastdk replied 1 year ago.
Hello, The problem can either be loss of fuel or loss of spark. By the sounds of your comment it seems your ignition coil is breaking down and losing spark. Is your engine a single cylinder or Twin cylinder, Most 15 Hp engines are Single cylinder.
Customer: replied 1 year ago.
my engine is a single cylinder
Customer: replied 1 year ago.
the ignition coil would cause backfiring?
Customer: replied 1 year ago.
(Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  gofastdk replied 1 year ago.
Yes when a coil fails, sometimes it will give a back fire. When it stops, immediately check for spark. You can have another spark plug handy and just remove the plug cap off the spark plug on your engine and hook another spark plug in the cap and ground the body of that plug to the engine. Then turn engine over and see if you have spark. If no then your coil is bad. replace it!
Customer: replied 1 year ago.
ok what do i check if i have spark?
Customer: replied 1 year ago.
hello will i have to Waite another day? if i have spark after backfiring and stalling what should i check next?
Customer: replied 1 year ago.
hello are you still helping me please respond soon thank you
Expert:  gofastdk replied 1 year ago.
If you still have spark, then it must be lack of fuel. A fuel cap could be bad. Fuel caps have a vent in them, if the vent gets plugged then it will cause a vacuum in the tank and not allow fuel to flow. But that failure time can very by the amount of fuel in the tank. To test it, when unit shuts down, loosen the fuel cap. If you hear a rush of air into the tank thru the cap, it should fire right back up after that without having to wait 5-10 min. It could also be a fuel pump breaking down when hot. That is if you have a fuel pump. If your fuel tank is higher than the engine it may be gravity fed with out a fuel pump.
Customer: replied 1 year ago.
i have a fuel pump.and my gas tank is in the back under the seat with the fill opening is on the left fender and its very large opening
Customer: replied 1 year ago.
someone said that it might be the head gasket? but it don't smoke maybe a puff of white smoke once an a while.
Customer: replied 1 year ago.
did i also tell you that the backfiring is thru the carb. mostly
Expert:  gofastdk replied 1 year ago.
First lets try the steps I have asked first. These are all the steps in diagnosing the problem. But these steps must be done moments after the engine shuts down. Both the spark test and the Fuel cap test.
Customer: replied 1 year ago.
hi i cut grass for 3 hours on and off let it sit for 3 hours it started let it idle it died thought ran out of gas but it had a 1/4 tank so added some anyway drove it in my shed an it stalled i loosened the fuel cap an still backfired hooked up a spark plug tester and it lit strong plenty of spark but also smelt a lot of fuel but kept it on slow throttle an it backfired a half doz. more times and it started now it starts fine wtf with this engine can you please help before it get a dynamite stick for its fuel?
Expert:  gofastdk replied 1 year ago.
Okay Moving forward with your latest feedback, With all that backfiring, it sounds like you have water in your fuel. That answers all the inconsistency of the failures. Drain a good amount of the fuel out threw the fuel line, not sucking it out. Drain it in to a see thru glass jar, and let it sit for 5 min. If there is water in it, it will settle on the bottom of the jar and puddle up. I water is found, then your complete fuel system need drained and dried out, including the fuel in the carburetor bowl.
Customer: replied 1 year ago.
NO water in the fuel i use the same gas in my other lawn tractor plus its a new filter i work on small engines and also 2 cycle but i never came across this problem tats why i'm paying to ask an expert. someone said its a head gasket but the leak down test is fine so i don't think its the head gasket and not a lot of smoke except maybe a puff at start up that's it can you help also it has a new carb.
Customer: replied 1 year ago.
is anyone here that can help me?
Expert:  JohnF2015 replied 1 year ago.
You have a Kohler Command single cylinder engine.This engine has hydraulic valve lifters, there is not valve adjustment on this engine.
Expert:  JohnF2015 replied 1 year ago.
Reading through the previous post it sounds like the engine could have an ignition coil going bad. Have you tried replacing the spark plug?
Expert:  JohnF2015 replied 1 year ago.
You indicate that you have done a leak down test, How did this turn out?
Expert:  JohnF2015 replied 1 year ago.
This engine also has hydraulic valve lifters, you may have a valve lifter sticking periodically which would also explain the backfire.
Customer: replied 1 year ago.
its a new plug and yes it has hydraulic lifters,also new carb. new fuel filter
Customer: replied 1 year ago.
yes their is no adjustment for valve lash or gap
Customer: replied 1 year ago.
if it is a bad or stuck lifter what would it take to fix or replace it ? a complete motor tear down would it be intake or exhaust or both and how difficult can that be ? any help will be greatly helpful i'm very mechanically inclined and understand instructions very well the leak down test was in the normal range if i remember but i will do another test in the morning. i hope you can help me out john thank you for responding
Expert:  JohnF2015 replied 1 year ago.
If you are going to replace the valve lifters I would replace them both while you are doing the job. Unless you have a valve lifter removal tool you will have to pull the head off to do this(and even with a tool you end up pulling the head sometimes). This will all depend on age of the machine and design of the head, some of the older heads were designed in such a way that there isn't enough of a hole to pull the lifter out without removing the head, the newer heads were redesigned so that the push rod area has a larger space to where you can actually pull the lifters with a tool without removing the head.Most likely your problem will be with the intake lifter but like I said you are better to replace both when doing this it will save you in the long run.It is obviously and easier job if you have a lifter tool and you have the newer style head but either way it is not an extremely difficult job.You will need two new lifters they are both the same, a new head gasket if you have to remove the head and possibly carburetor mount gaskets and a tube of silicone to reinstall the valve cover(Kohler uses silicone on the valve cover rather than a gasket).You will want to be sure to torque the head bolts back to proper specs if you have to remove the head. Your local parts store or repair shop should be able to provide you with the torque specs, just ask when you go to purchase your parts.
Expert:  JohnF2015 replied 1 year ago.
Thank you if has been a pleasure to work with you.Thank you for choosing justanswer.
Customer: replied 1 year ago.
the lawnmower is about fifteen years old
Expert:  JohnF2015 replied 1 year ago.
That's right around the time that Kohler was making the change on those heads so if you are lucky you have the new style head and won't have to remove it in order to replace the valve lifters. You will still have to remove the valve cover either way so you will at least need a tube of silicon to reinstall the valve cover and the two valve lifters.
Customer: replied 1 year ago.
i just did the leak down test it moderate about 45% on the gauge
but i don't hear a lot of air any where
Expert:  JohnF2015 replied 1 year ago.
Do you have any issues with the engine using or burning oil?
Customer: replied 1 year ago.
no get a puff of smoke at start up but doesn't really burn oil
Expert:  JohnF2015 replied 1 year ago.
I wouldn't be concerned about the leak down at this time. If you aren't burning oil and the engine runs good at times then I think you will find that the valve lifters are causing you trouble.
Customer: replied 1 year ago.
ok yes seems like it the other tech before you sad might be a fuel pump
Expert:  JohnF2015 replied 1 year ago.
No, normally the fuel pump either works or it doesn't, so I don't think that the fuel pump is an issue.
Customer: replied 1 year ago.
ok i'll look into the valves but i'll need a special tool correct ?
Expert:  JohnF2015 replied 1 year ago.
You don't have to have it. It would make the job easier if you have the newer style head. The only thing that it will give you an advantage on is not having to completely remove the head if you have the new style head. If you have the old style head you are going to have to remove it regardless, the valve lifters won't come out through the old style head therefore you have to remove the head.You can do the job without the lifter tool you just have to remove the head.
Expert:  JohnF2015 replied 1 year ago.
Thank you it has been a pleasure to assist you today.Thank you for choosing justanswer.
Customer: replied 1 year ago.
ok thank you if i have anymore ?'s can i get back to you?
Expert:  JohnF2015 replied 1 year ago.
Yes you certainly can. All you will need to do is come back to this post and we can continue our conversation.You will be asked to rate your experience and satisfaction with the help that you have received. If you can go ahead and do so it would be greatly appreciated.Don't worry you can still come back to this post and continue conversation if needed even once you have rated your service.Thank you.
Customer: replied 1 year ago.
hi john i'm ordering new lifters do they need to be primed before installing them?
Expert:  JohnF2015 replied 1 year ago.
No, they will come with a small tube of assembly lube, just apply the lube to the outer diameter of the lifter and slide them into the block. Everything will take care of itself when you crank the engine over to start.