engine problem

[TobyU]

I had a mower do this one time, the gas tank had some bugs and rubber from the gas cap, blocking the gas flow to the carb. I removed the tank, cleaned it out and it's been running since.

Very true that this can happen but we should always diagnose our problems before we waste time and money on repairs that may not be the problem.
People with a decent amount of experience with engines can usually tell whether one is a fuel or ignition issue when it dies. Ignition is usually abruptly like you turn the key off or sometimes we'll have a few crisp stutters or pops but it will be different than fuel starvation issue where it will more slowly lose power and get weak before it shuts off.
For the past 10 years or so, maybe longer, most of the problems are fuel related for whatever reason.
Could be gas tank, fuel lines, blockages, carburetor solenoids, debris and floating stuff in the carburetor, restricted Jets etc but it's far more common than ignition.
The go-to even today is still to try a new spark plug which is just a waste of time 95 plus percent of the time.
The most efficient way to start a diagnosis is to give it an external fuel source or more fuel.
You will often find that when one starts to mess up if you add choke quickly maybe not full choke but half to three quarter choke but some type of choke amount that if it starts to smooth out for at least a couple of seconds then you can guarantee it's a fuel issue.
Then you can do things like the easiest first of popping the fuel line off the carburetor to see if you have good flow sometimes having to crank it if you have a fuel pump or pulsator pump.
Then you can remove the fuel solenoid on the bottom of the carb and simply hold your finger on it if you have to to see if that solves the problem because it does a decent percentage of the time. Then you can either replace it fix it or whatever.
You should also try the the easiest fix when it is the problem of checking the fuel cap fit. I have found so many with a big chunk of dirt colored dust packed in there that you can literally suck out if you suck on them with your mouth and it's like a hard pebble.
You can use a small wire or air compressor blow gun tip to clear them out just don't blow the cap apart but usually you're okay.
I had an stx38 a few years ago that somebody brought me that wasn't getting enough fuel through the fuel line so the car bowl level was getting low. I found three ladybugs hiding down the fuel line.
They had probably been in there for years but the tank looked pretty clean. When I got around to blowing backwards on the fuel line the ladybugs and some other crap blew up into the gas tank.
I also had a Cub cadet zero turn that had so much grass that had worked its way down into the fuel line about 2 in past the exit point of the tank that it would start for fuel and not stay running with the blades on under load.
Even though these tanks are supposed to have a strainer or whatever it doesn't mean it always works. And both of these instances it was a very quick easy fix once you do what the problem was..
Luckily I diagnosed it quickly by pulling the fuel line off of the carburetor and found it was very much reduced flow.

 

[Dpmulvan]

Modern magneto coils have a timing chip inside since around 1990 when Atom Industries patient ran out
You can not test the primary coils because the chip is in the way
It works for car coils,
It works for coils that have points
It does not work for coils that have embeded chips
As coils ( called armatures when the embed a 10¢ the charge $ 50 ) are not repairable the only test worth doing is to remove the kill wire to ensure the coil is the problem & not the stop switch or any safety switch .
This is a forum for serious repairs not for spreading old wives tales & urban myths, that is what Face book & twitter is for .

ive checked literally hundreds of coils this way over time...if it reads between 2.5K and 5k ohms...its good...outside this range is bad...worked every time...outside the lower and upper limits has identified if the coil is bad every time without exception...been doing this for almost 50 years...

ive checked literally hundreds of coils this way over time...if it reads between 2.5K and 5k ohms...its good...outside this range is bad...worked every time...outside the lower and upper limits has identified if the coil is bad every time without exception...been doing this for almost 50 years...

The proper way to test a coil is with an oscilloscope You cannot test a coil properly with an ohm meter.

 

[TobyU]

The proper way to test a coil is with an oscilloscope You cannot test a coil properly with an ohm meter.

True. I'll hang out a coil is just the most very basic test a person can do and you should never rely on it too much.
Even with an oscilloscope you still don't know if the coil will get hot and break down or vibrations will take an effect etc but it's still better than just an ohm test.
Even if you had a higher quality more realistic style coil tester which they do make and you might remember some of them from some automotive displays for coils years ago... It was one of these you would have to let it run for a period of time to make sure it wouldn't break down.
All of these static tests are kind of moot.
The best way to diagnose anything is to get it to act up, which these things usually do pretty consistently, and then troubleshoot it from there like checking for spark..
Strange things happen and real use applications some that aren't supposed to.
The oscilloscope reminds me of an alternator I had one time and it's really the only one I've ever had that did this that was intermittent.
I'm sure it would have fully got out in a few days or miles but when I noticed the problem it was charging and then not charging and back and forth. It ended up being the copper rings for the brushes but it was RPM dependent. At certain RPMs it would charge fine and others it wouldn't. If this alternator was put on a tester even with a oscilloscope as opposed to the junkie ones the auto parts stores use it still would have been spun at a set RPM and might have been right where this alternator happened to be charging but put it on the vehicle where the RPMs are highly variable it would go in and out with the battery light coming on and the volt gauge dropping down repeatedly.

 

[bertsmobile1]

The proper way to test a coil is with an oscilloscope You cannot test a coil properly with an ohm meter.

And that is just for the coil section you also need a signal generator to trip the Hall effect trigger .
And depending upon the actual circuit used some need a magnetic field generator.
And because the trigger is potted in then you really need to remove the potting mix to get to the coil proper .
However they are in effect not repairable so it is a moot point .
It either works or it does not work.
You can test the secondary windings, because the coil is in fact a transformer , the High tension lead & cap with an ohm meter but again most of the newer ones are soldered onto the secondary windings so again not replaceable .
When Briggs & Stratton took over Victa they put the price of the magnetos up to $ 180 ( Wholesale ) to make the old power torque engines too expensive to repair so I spent a lot of time looking for an alternative or method of repairing them .
Mower magneto coils have an easy life & the coil itself very rarely fail it is the timing chip that fails .
Chips cost around $ 1 ( Aust) to make and you buy them for $ 15 down here ready to fit so removing the chip from a dead coil and retro fitting the previous external chips became a viable repair method , thus I have pulled a lot of them apart.
The early ones ( made in Italy or Argentina ) had the HT fitted into a brass screw so it was easily replaceable.
The latter ones ( made is China ) have the HT lead soldered to the windings so is not replaceable without destroying the case

 

[laurin800]

Your magneto is bad. When it gets hot it breaks down. A fairly simple fix. Get your Model, Type, and Code information and go to Amazon. The part should be under $40 even if you want the genuine factory article or about $20 for a Chinese knock-off that will probably do just as well. The replacement is an easy afternoon job for anyone with a basic tool set. I don't remember the exact specification, but you'll want to be pretty careful setting the air gap. It's been a couple of decades since I shut the shop down. Should be available with a Google search as long as you have the Model, Type, and Code number.

Magneto? Maybe in the 60’s

 

[shadetree#1]

regeland:
What is the latest results of your testing?

John Deere LA 115 19.5 briggs and stratton starts cold runs 5 minutes and cuts off. loses spark. Has a new spark plug new gas filter, new air filter. Anyone else have this problem?

 

[Dpmulvan]

I had a brand new zero turn with a Kohler motor that would run for 10 minutes and shut off, dealer said they had this problem with others and it was a casting flaw that was blocking a hole i forgot where. They shipped it back to me and Instead of using new valve cover gasket used red silicone too much I might add. Anyway got mower back did the same thing wasn’t fixed. I got pissed and called Hustler the rep came out with a new mower with a Kawasaki on it and took the Kohler back. Never did find out what it really was, it’s a shame because my older command from the 90’s is still running like a top after I did a valve job.

 

[TobyU]

I had a brand new zero turn with a Kohler motor that would run for 10 minutes and shut off, dealer said they had this problem with others and it was a casting flaw that was blocking a hole i forgot where. They shipped it back to me and Instead of using new valve cover gasket used red silicone too much I might add. Anyway got mower back did the same thing wasn’t fixed. I got pissed and called Hustler the rep came out with a new mower with a Kawasaki on it and took the Kohler back. Never did find out what it really was, it’s a shame because my older command from the 90’s is still running like a top after I did a valve job.

I've had 3 Chinese Loncin engines on riders that had a piece of wadding pushed up into carb inlet nipple. The 1st time was surprising, the 2nd even more that it happened twice....now I check anytime the symptoms are fuel starvation.
Point is, you diagnose by symptoms and methodically check in logical way until you find the reason for the symptom.

 

[TobyU]

Magneto? Maybe in the 60’s

Magneto, coil, ignition module

Magneto? Maybe in the 60’s

Magneto, coil, ignition module, ignition coil.. Are all commonly used interchangeably. Whether it's technically correct or not...it doesn't matter. People refer to the thing that the spark plug wire comes out of as all of these terms so as long as we know what they mean.

Magneto? Maybe in the 60’s

,

 

[shadetree#1]

TobyU says:
People refer to the thing that the spark plug wire comes out of as all of these terms so as long as we know what they mean.

or it's sometimes also termed:
Check the thingamajiggy with the wire coming out going to the other thingy.