OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Briggs & Stratton - 13hp - No Spark

Hi folks, my Briggs & Stratton 13hp engine in my Husqvarna LTH 130 Ride On, had an intermittent cut out issue when it got hot.

So my old brain thought, fuel issue or spark issue.

Fuel was fresh, fuel bowl was spotless, fuel filter was replaced just in case.

So then I checked for a spark at the plug and there was no spark at all when it cut out. So I replaced the spark plug but that didn't fix it. So I bought a new coil (from here) and it started 1st go after fitting the coil. Then I went to start it a week later to use it to mow block and it failed to start. There was No spark at the plug and No spark from the coil lead to the engine block. I used the old business card to set the air gap which has worked many time on all engines, so I guessed that part should be OK.

So next I tried unplugged the kill switch wire from the coil but that didn't fix it either, so now I'm stumped.

Can anyone please shed some light on what else it could be?

Hi Steve,

It's worth checking your flywheel magnet strength with some steel or a large flat blade screw driver should do.

Occasionally I get flywheels that have lost their magnetism

.I'm assuming you haven't bolted the coil upside down.

If there is still no spark (i usually check with a timing light) It could be a faulty coil ,it's worth checking the resistance
of the coil with a multi-meter..

https://pushmowerrepair.com.au/briggs-and-stratton-ignition-coil-testing/

If the resistance test fails then exchange the coil for a new one, I bought 2 new coils (not from here ) and they both
failed within minutes of installing them.

Cheers
Max.

Thanks Max for your assistance here and for providing the link to coil testing.

I do have a second question relating to your reply.

You mentioned about bolting the coil upside down, is that something that matters?

The kill switch connection is on the bottom like the old one was but on reflection (i'll have to check it again) I think there were spade terminals on both sides of the new coil?

Also I didn't fit the thin black wire than came with the new coil, I used the old Kill Wire to the new coil. Would that make a difference?

I'll get back here with the next findings.

Cheers

my way of checking spark is to put the plug onto the lead, as usual, outside the engine (of course) and put an allegator clip joined to another with wire, clip one onto the plug, the inside bit, and the other to earth, a part of the engine. that avoids getting zapped holding the plug.
good to see that resistance test, I have 4 coils over time and another one in the post today.
never to old to learn, and make mistakes.

I note the new coils I have purchsed in the last couple of years no longer have stamped on them 'this side to cylinder' which is the bottom. nothing on them at all.

Hi Steve and Peter,


Yes Steve if you bolt the coil on upside down this will induce a magnetic field in the armature the wrong way
for the coils windings to produce the correct high voltage in the secondary windings.

Yes on the original coil the kill switch wire is on the bottom of the coil.

Some replacement coils are different but if the spark doesn't look good you could try it the other way.

The old kill switch wire is fine as long as it's not damaged.

Cheers
Max.
.

Hi Guys, thank to both of you for your help here.

I removed the new coil as well as the old coil and tested both of them, here are the ohms readings @ 20k:-

New Coil = 5.25
Old Coil = 4.55

I replaced the coil in case the old coil was failing after running the mower for about 15 - 20 minutes and it would simply die, with no spark. I had also uplugged the kill wire from the old coil and tried to start the mower, again no spark. That should have isolated all the other safety switches on my ride on and left me with:- it must be the coil.

The new coil worked the very 1st time after I fitted it, the engine started straight away. A few days later and nothing, no spark at all at the plug or the coil lead, using a spark tester.

Any other ideas would be helpful?

Here's 3 images of both Old & New Coils.

A quick update..

I put the old coil back and set the air gap using my trusty business card method and you guessed it, the engine fired up straight away without the kill switch wire connected. Luckily I had turned off the fuel tap so it stopped pretty quick..

Then I connected the kill switch wire and again, it fired up without issue.

Can anyone help me understand what the hell is going on here?

Where I take the mower is a 3 - 4 hour drive from home each way and I have to mow 1500 square meters of shortish grass. With plenty of breaks of course so I'm not overworking the mower at all.

If it still cuts out without spark while I down there, I just might burn it on the spot. lol

Hi Steve,

I've had lots of coils and spark plugs break down once they get warm after running for a few minutes.

The proper way to test a coil is a load tester that most people don't have ,when the coil is really bad it
will show up just with an ohm meter ,the only other way is to check for spark or check the resistance of
the coil after the motor stops.

You said you had no spark after the motor was hot and as long as there is no seat kill switch or other kill switch shorting out
( sounds like there can't be if you have run with the coil kill wire disconnected and it cuts out ) and if it's not a fuel problem
like the carby not getting fuel as some motors have a electric fuel cut out.

It may be worth using the mower close to home or just run the mower for half an hour if it cuts out with no spark ,send the coil back for a replacement.

Cheers
Max.

Thanks Max, I'll ask at my local mower shop to see if they have a load tester where they can test both coils under load to see if there is an issue with either of them.

The last time it cut out while mowing with the old coil in place I did check for spark and there was none, not at the coil, not at the spark plug and not with the kill wire disconnected.

Now that very same coil is working as it should with and without the kill wire connected.

The flywheel magnet is very strong, I stuck a 5/16' spanner to the magnet and it took 2 fingers to get it off. So that part is OK.

As for the fuel system, there is no fuel cut off that I can find and nothing mentioned in the parts manual.

I have a fuel tap installed in line.

I will try what you have suggested and see what happens.

Cheers

Steve

Hi Steve,

Some engines have the fuel cut off solenoid in the carby.

The coil load testers I remember were for points ignition where you could get to the wires, not sure if they
would work with the electronic coils as you can't get to the wires when the coil is completely molded in
plastic.

The only other thing I usually do is when fitting a coil is to get some sand paper and sand the metal core
of the coil where it mounts onto the alloy on the motor and clean the alloy where the coil touches the motor with sand paper,I usually also clean under the heads of the 2 coil bolts with sand paper and clean on the coil where the underside of the bolts touch the coil but after sanding all those parts to get a good earth wipe all sanded parts with a clean rag before assembling as sand paper has silicone which is a poor conductor and wiping with the rag takes away the silicone, you could wire brush the threads if they are dirty too

May have just been a bad earth of the coil.

Cheers
Max.

Thanks Max, i have done and will do all you have suggested in your many replies to my questions and I thank you for taking the time to help a novice small engine repairer. I have too many years on larger engines (and mechanical work) and now can't handle the big jobs, so I have switched to the small stuff and love it. I get to work mostly on a bench rather than under a bonnet or under a vehicle.