Engine Won't Start After Compression Test

[primerbulb120]

These are the possibilities I've been able to come up with:

1. Intake valve is not opening for some reason.
2. Intake gasket is messed up somehow.
3. Coil could be bad or gapped incorrectly.
4. New spark plug could be faulty.

I am leaning towards 3 or 4 as the cause of the problem. You got it to start and run good ONE TIME since the compression test, right? Coils and spark plugs can suddenly go bad, and they can also work intermittently.

 

[MonkeyCam]

These are the possibilities I've been able to come up with:

1. Intake valve is not opening for some reason.
2. Intake gasket is messed up somehow.
3. Coil could be bad or gapped incorrectly.
4. New spark plug could be faulty.

I am leaning towards 3 or 4 as the cause of the problem. You got it to start and run good ONE TIME since the compression test, right? Coils and spark plugs can suddenly go bad, and they can also work intermittently.

I think it's the coil. I've eliminated everything on the list but that. I've also eliminated the carb as the problem. In my surfing, I came across a guy on YouTube w/ this same engine who has a video on how to replace the coil, & he says that these Kohler XT engines are known for the coils going bad. I ordered a new one several days ago, & it should arrive tomorrow. After I install the new one, I'll post the results.

 

[primerbulb120]

Good idea. :thumbsup:

 

[TobyU]

If you check for spark with plug grounded to engine and it is decent it would be unlikely to be a coil, but strange things happen.
I've had a few weak ones that would only run right with a smaller plug gap like . 022- .025.

 

[MonkeyCam]

I changed the coil, & it started & ran on the very 1st pull--even w/out using starting fluid. :biggrin:

There were a couple of things that made this so confusing & hard to diagnose:
1. The engine ran fine until after I performed a compression test, then it suddenly wouldn't start. Apparently that was just a very misleading coincidence.
2. I was still getting a spark both when I used a spark tester & when I grounded the spark plug to the engine. Obviously, it was an *insufficient* spark. I'll remember that lesson for future reference.

My experience confirmed what I'd read on the Internet: Kohler XT series engines are known for the ignition coils going bad. You guys might want to file that factoid in your mental Rolodexes.

Finally, a heartfelt thank you to those who took their time & gave me the benefit of their knowledge to help me solve this maddening problem. I *really* appreciate it. :thumbsup:

 

[TobyU]

Glad you figured it out. I don't really know if xts are known for coils but there are so many millions of them out there I'm sure you can find quite a few instances of them going bad.
I service 15 or 20 per season and have not had a bad coil yet. I did have a bad coil on a Kohler 7000 series that was made September of 2015. This one was bad last summer so it only made it a year. Also had a couple of duraforce lawn boys go bad and an alarming number of older Kohler commands from around 2003. I figured those are just due to age.

 

[7394]

:thumbsup:

 

[ILENGINE]

I changed the coil, & it started & ran on the very 1st pull--even w/out using starting fluid. :biggrin:

There were a couple of things that made this so confusing & hard to diagnose:
1. The engine ran fine until after I performed a compression test, then it suddenly wouldn't start. Apparently that was just a very misleading coincidence.
2. I was still getting a spark both when I used a spark tester & when I grounded the spark plug to the engine. Obviously, it was an *insufficient* spark. I'll remember that lesson for future reference.

My experience confirmed what I'd read on the Internet: Kohler XT series engines are known for the ignition coils going bad. You guys might want to file that factoid in your mental Rolodexes.

Finally, a heartfelt thank you to those who took their time & gave me the benefit of their knowledge to help me solve this maddening problem. I *really* appreciate it. :thumbsup:

Had a CV23 come in on an exmark that won't start and had fire at the plugs when grounded and also with another tester, The correct Kohler tester showed both modules are bad.

 

[motoman]

There must be more to the pattern failure. For instance if the coil is nearer the head than other setups. The Intek V at least has the coils mounted on very large castiron "heatsinks" which no doubt help keep the coils below their failure temp. Also viewing a spark with naked eye , or cold, can mask a failed coil which will not perform at hot or under compression. These things drive us all crazy, right? And again, as others recommend , do not buy anything but brand name coils. The cheap ones may never have been turned on, and contain defective components. Even dealers get lot failures with the "major brand" electronics and do not make recalls, only angry customers.

An article on electric cars mentioned a heat tolerance of only185F which I believe is too low, but it is something that affects lawnmowers, electric cars and your stereo.

 

[bertsmobile1]

Pattern of failures ?

I get more engines in with sever head damage from overheating with perfectly good coils than I do with faulty coils.
The whole one piece coil & module is a planned obsolessence thing.
The points coil & hall effect trigger set up is 2/3 the price of a modern combined unit and a lot more reliable.
Spark testers are just that .
I have 6 different ones but one would not expect a home owner to have $ 200 worth of test gear as most either work or don't work.
Of the modules I replace around 1/2 simply have a broken connector in the HT lead and the local Mens Shed digs the old one out & replaces them.
They rebuild old mowers for fun and usually give them to pensioners so anything that costs only time is good for them.