Bad Ignition Coil Symptoms Lawn Mower: 6 Fixes & Replacement Guide. Lawn mower no spark
SRX75 No spark / Weak Spark
Hello, I am hoping to find some help from all the experts on this site. I have a 1995 SRX75 with the 9.0 HP FC290V engine I was having issues with not getting any spark at all, replaced the coil and still no spark. (Testing by removing kill wire from coil, and then resting spark plug against engine head bolt for ground) I thought Bad Plug maybe? (doubtful but hey who knows)
Bought New plug set it with.030 gap, no spark still. I have even stuck a screwdriver and cranked it while holding and I felt a nice shock. However. no spark with testing with plug. I took a multimeter and testing voltage from the plug wire and getting around 50 volts, from my understanding it should be a lot higher than this I was thinking possible bad ground on the coil so I removed coil sanded down post so nice and clean, cleaned magnet on flywheel too. put it all back together with airgap set with thickness of business card. Still no spark, same 50 volts.
So here is where i am confused. reading other forums, people have mentioned and ignitor ( im not sure what this is, does this model have one) I thought newer coils had all that built in. Shouldn’t I get a nice spark with the kill wire unplugged or is there something i am missing? I have tested with on and off and get same results. What does the ignition module do? i thought it just grounded the coil out when powering off engine? am I wrong or could this be causing a weak voltage from coil.
Any advice will be much appreciated. Thanks in advance.
Chuckv
Here is the wiring diagram for the RX/SX 75 mower.- don’t know if your version is substantially different:
It does sound like you have a bad igniter. Here is its location and how to test it:
This last, larger file should cover the engine topic pretty well.
Hope these help.- let us know what you find.
sandersoncw55
Here is the wiring diagram for the RX/SX 75 mower.- don’t know if your version is substantially different:
It does sound like you have a bad igniter. Here is its location and how to test it:
This last, larger file should cover the engine topic pretty well.
Hope these help.- let us know what you find.
Chuck, Thanks for your time, I am unable to locate an ignitor on this engine. From the looks of the wiring diagram it should lead right off the coil, however the lead goes back towards the relay box located near the starter solenoid. According to John Deere Parts website the part should look like this:
I have seen these on other engines i have worked on and they are typically mounted to the engine itself near the starter. I checked mine and nothing there, there are only 3 wires that come from this engine and go to the body of the tractor. 1. white wire from the coil to the relay box (kill wire) 2. yellow wire from the alternator located under the flywheel 3. the thick red wire going to the starter from the starter solenoid.
I am lost, why does John Deere parts diagram show the part but i dont see it. am i looking in wrong location?
Chuckv
I took a quick look at the JDParts on-line parts catalog PC2292 for the SRX75 and SRX95, which shows both the 9HP FC290V and the 12.5 HP FB460V engines being used. I don’t know if the larger engine is found on any SRX 75 models. but that could give another variation that might impact the presence or absence of an igniter. It looks like the suffix.BS25 version of the larger engine has an igniter, but the.DS35 and.ES34 may be different (uncertain from the limited information found there. )
What is the engine type and the full model/version number on it as used in your mower? If you have pictures of the “module” you describe that may be helpful as well. I can’t find any such module in PC2292.
sandersoncw55
I took a quick look at the JDParts on-line parts catalog PC2292 for the SRX75 and SRX95, which shows both the 9HP FC290V and the 12.5 HP FB460V engines being used. I don’t know if the larger engine is found on any SRX 75 models. but that could give another variation that might impact the presence or absence of an igniter. It looks like the suffix.BS25 version of the larger engine has an igniter, but the.DS35 and.ES34 may be different (uncertain from the limited information found there. )
What is the engine type and the full model/version number on it as used in your mower? If you have pictures of the “module” you describe that may be helpful as well. I can’t find any such module in PC2292.
Chuck, I looked all over this tractor and do not see an ignitor. the engine is the 9.0 HP FC290V engine. here are some pics of all the tags on the mower.
I took a pic of the wiring the best i could.
As you can see here, following the two wires that come off the engine go straight back to the harness, no ignitor in the wiring.
This think has me stumped, I am starting to think the coil that i received is bad. Is there a way to test it? Also is it possible that the magnet on the flywheel has just become weak overtime causing the coil to spark, but just not hot enough to cause the plug to spark. As mentioned before it puts out about 50 volts right off the coil. Is this normal i am assuming not.
Any further help you could provide would be greatly appreciated.
Chuckv
OK-let’s go back to basics for a moment here to establish some background on how an Igniter works. There is some pretty sophisticated solid state circuitry inside the Igniter that both senses voltage and switches current rapidly to ground at the instant the plug should spark. here is what I think is supposed to happen.
The Igniter looks quite simple and has a single terminal plus a metal case or mounting tab that needs to be firmly attached to the engine (which establishes a ground connection to that tab.) That single terminal usually has two wires going to it.- one is from the coil primary and the other goes to the key switch terminal labeled M for magneto. The key switch grounds the Igniter terminal and hence the coil primary when the key is the OFF/STOP position. In other positions of the key switch the M terminal is not grounded by the key switch.
In operation, the moving magnet on the flywheel induces a voltage in the spark coil primary that increases until it reaches a limit that can be sensed by the Igniter terminal (I recall this is around 40 volts, but can’t find an authoritative reference. ) At that point the circuitry inside the Igniter switches on (conducts) such that the winding on the coil is instantly grounded. It is that rapidly collapsing magnetic field in the primary winding that induces a very high voltage in the secondary winding of the spark coil assembly that creates a spark at the gap in the plug. A missing or failed Igniter would certainly cause the spark at the plug to be woefully insufficient.
Trace the small wire from the magneto coil on the engine (not the high voltage wire going to the spark plug) all the way to the key switch and let us know what you find. If that wire goes instead to a different module or printed circuit card, maybe your mower is a very late model that has another module doing the work of the Igniter. In that case that module may be open and not triggering in the manner a working Igniter does.- I understand Igniter failures are mostly open circuit failures.
You can also verify that the gap from the flywheel to the magneto is set properly, as it effects function as well as engine spark timing. It should be 0.012 inches as shown here:
Bad Ignition Coil Symptoms Lawn Mower: 6 Fixes Replacement Guide
The ignition coil, which also goes by the spark coil, is essential in starting a vehicle’s engine. It plays an important role in the ignition system overall.
If your riding lawn mower is difficult to start, if the engine only starts when you jiggle the plug wire, or if it performs poorly, it may be time to replace the ignition coil.
This article will teach you how to recognize the signs of a malfunctioning ignition coil in your lawnmower, as well as the most prevalent causes of failure and the solutions to those concerns.
HOW TO DIAGNOSE A BAD COIL ON JUST ABOUT ANY SMALL ENGINE!
Why Ignition Coil Is Important?
24 584 45-S Ignition Coil compatible with MIA11292 Kohler CH18 CH20 CH22 CH23 CH25 CV18 CV19 CV20 CV22 CV22S CV23 CV25 Replace 24-584-01S
Db Electrical IBS3004 Ignition Coil Compatible with/Replacement for Ibs3004 Ignition Coil Compatible with/Replacement for Briggs Stratton 802574 493237
A lawnmower’s ignition coil is important since it is what transfers power from the battery to the spark plug, producing the spark that drives the engine into gear.
There won’t be any burning of oxygen and fuel in the combustion chamber for one or more cylinders if the ignition coil isn’t working. Because of this, they will refrain from firing. In such a case, the engine won’t get the juice it needs to move forward or even start.
Lawn Mower Bad Ignition Coil Symptoms
If your lawnmower’s ignition coil is bad, you may notice some of these symptoms. Don’t worry, I have added the fixes also.
Symptom-1: Mower Shuts Down Immediately
If the ignition coil is bad, it may cause the engine to shut down immediately or run very poorly. Depending on the severity of the problem, the engine may not even start.
If the ignition coil is bad, it will not effectively transmit the spark necessary to ignite the fuel mixture. This can cause a misfire, which will result in the engine shutting down.
The ignition coil on the lawn mower sometimes became overheated, resulting in an abrupt stop-down.
The Fix
A qualified mechanic should inspect the ignition coil, spark plugs, and other components to diagnose and repair the problem. If the problem is found to be with the ignition coil, it should be replaced.
This, however, is the sign that a faulty ignition coil presents the vast majority of the time.
Symptom-2: Mower Not Turning Off
The most likely cause of a mower not turning off due to a bad ignition coil is a faulty ignition switch. This can cause the ignition coil to stay energized even when the switch is in the off position.
The Fix
To fix this issue, the ignition switch should be replaced. If the switch is not the problem, then the ignition coil may need to be replaced as well.
It is also possible that the wiring to the ignition coil may be faulty, so this should be checked as well.
Symptom-3: Mower Begins Then Dies
If the engine starts and then dies immediately, it could be due to a bad ignition coil. The ignition coil is responsible for supplying the spark to the spark plugs. If it is not working properly, the engine will not be able to sustain itself.
The Fix
The ignition coil should be checked and replaced if necessary.
Symptom-4: Engine Misfiring
Bad ignition coils can cause lawn mower engine misfires. The lawn mower’s ignition coil sparks the engine’s fuel. A misfire occurs when the coil fails to spark the fuel.
The Fix
Check the spark plug wires for appropriate connection and condition to detect and fix misfiring. Check the spark plug next. Replace if worn, corroded, or damaged.
If the spark plug and wires are fine, the ignition coil is the issue. Use a multimeter to test continuity. Coils without continuity must be changed. Misfiring should stop after coil replacement.
Symptom-5: Poor Fuel Economy
The bad ignition coil of a lawn mower affects fuel economy because it will not be producing a sufficient spark to ignite the fuel. This means that the fuel is not burning efficiently, resulting in a decrease in fuel economy.
Additionally, the spark plug will not be able to ignite the fuel quickly enough, resulting in an increase in exhaust gases that can further reduce fuel economy.
The Fix
To solve this issue, the ignition coil should be replaced with a new one.
Symptom-6: Engine Cranks
A faulty ignition coil may be the reason your lawn mower to crank but not start. The engine’s ignition coil sparks the combustion chamber’s fuel. Bad ignition coils can also prevent engine start-up.
The Fix
Check the spark plug to find a bad ignition coil. Ignition coils usually cause no spark. Measure the ignition coil resistance with a multimeter. If the coil’s resistance is outside the range, replace it.
After replacing the ignition coil, check the spark plug gap and ignition timing to guarantee engine efficiency.
How To Detect A Bad Mower Ignition Coil?
Follow these simple instructions to determine whether or not the ignition coil on your lawn mower is functioning properly.
- Locate the ignition system’s rear lawn mower spark plug. Remove plastic coverings using a screwdriver.
- Remove the grounding wire and take the plastic boot off the spark plug.
- Clip one end of the spark plug tester to the exposed spark plug and place the long metal end into the plastic boot.
- Start the lawnmower. The ignition coil is functional if the tester sparks or the lawn mower starts.
How To Replace The Ignition Coil?
The first step in fixing all those issues is a new ignition coil for your lawn mower. Here is the process:
Remove Ignition Coil
- Locate the ignition coil first. Remove the electrical plastic pigtail connector. Handle the connector carefully.
- Open the coil-to-engine screws. Remove the coil gently.
- Twisting the insulator boot slide removes the spark plug. Careful—it breaks easily. Remove trapped parts with needle-nose pliers.
- Remove each ignition coil in the engine. Remove them slowly.
- Check the spark plug inner section and boot for oil or anti-freeze after removing the coil and spark plug. Fix leaks and contamination.
Test Small Engine Ignition Coil
- Swap the suspicious coil with the other coil to start testing. The suspect coil will fail if the other cylinder misfires.
- A multimeter can also test the ignition coil’s primary and secondary windings. Replace the coil if the multimeter result is greater than normal.
Lubricate and Reinstall Coil
- Apply dielectric grease inside the ignition coil insulator boot first. It will waterproof the coil.
- Push the coil onto the spark plug gently.
- Install coil bolts. Reconnect the electrical pigtail.
- Finally, lubricate the coil connector with a little. Lock and fit the connectors and tab.
Complete Installation
- Reinstall the remaining engine parts.
- Reconnect the negative battery cable.
- Check the lawnmower’s operation.
- After replacing the ignition coil, check it.
Precaution During Installation:
- Set the lawnmower’s parking brake.
- Flip the mower’s hood open.
- Get the engine cooled down to room temperature.
- When instructed, remove the negative battery cable.
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Learn the reasons why a lawn mower won’t start after winter or during peak season, and how to fix those problems.
Family Handyman
Introduction
Most of the time when a lawn mower won’t start the cause is a problem with the gas or the lawn mower carburetor.
What to Do if Your Lawn Mower Won’t Start
Whatever kind of lawn mower you’ve got, the last thing you want once winter finally lifts and spring has sprung is a lawn mower that won’t start.
If you’ve taken the proper steps to winterize your lawn mower, you’re far less likely to be dealing with such issues. It’s also why you should tune up your lawn mower at the start of every season. However, it’s not out of the ordinary to find your gas-powered lawn mower not starting from time to time, so it’s important to know why your lawn mower isn’t starting and how to fix it.
Project step-by-step (6)
Check the Gas Tank
Let’s start with the obvious. Before you have a heart attack pulling on the rip cord, you’ll want to check the fuel. Like any gasoline-powered engine, lawn mowers run out from time to time. Maybe you forgot it was running on fumes when you finished mowing last time. It sounds simple, but we’ve all overlooked the gas tank from time to time.
Even if there is gas in the mower, if the fuel’s been in there more than a month, that could be the problem. Gas sitting around too long in the tank can get contaminated with dirt and extra moisture.
So if your gasoline has been in the mower for more than month, drain the gas properly, dispose of it correctly, and fill up the mower with new gas. It may take quite a few pulls to suck the new gas into the lawn mower carburetor, so be prepared to clean and dry the plug a few more times.
Add fuel stabilizer when you fill up the tank to help protect the gasoline in there from dirt and moisture.
No spark on lawn mower engine. Ignition coil replacement
Family Handyman
Check the Spark Plug
Start by making sure the lawn mower spark plug cable is connected to the plug itself. It’s quite possible that it got pulled off there over the winter while the mower was being stored in the garage.
If that’s not the issue, the next step is to remove the spark plug to see if it’s wet. There’s no way the engine will start if it is. So clean the plug with carburetor cleaner and let it dry. Cleaning it with compressed air isn’t enough; you need a solvent to remove oil residue. If it’s really grimy and dirty, it might be best to change the spark plug.
Fertnig/Getty Images
Lawn mower won’t start troubleshooting video: spark plug and ignition problems video
If your lawn mower doesn’t start, the problem could be with the spark plug or ignition system. This video from Sears PartsDirect shows how to troubleshoot and fix spark plug and ignition problems, including using a spark plug tester to test the spark plug.
The video also shows how to use a multimeter to check for a short in the wire that connects the stop switch to the ignition coil, and it walks you through how to check the ignition coil and flywheel. Once you figure out the problem, we show you how to fix it. You’ll be cutting your grass in no time.
Hi, this is Wayne, from PartsDirect. Today we’re going to talk about some troubleshooting steps to determine why your lawn mower spark plug won’t fire.
Although walk-behind mowers can vary in appearance from this Craftsman 21-inch mower, they all work pretty much the same.
These are the tools and supplies you might need, depending on the problem.
Tools or equipment needed
- Ratchet and deep socket
- Spark plug
- Spark plug tester
- Nut driver set
- Multimeter
- Stop wire
- Clamp
- Feeler gauge
- Wood block
- Socket set
- Flywheel puller
- Hammer
- Flywheel key
Work in a well-ventilated area free of open flame or sparks.
Spark plug
Start by checking the condition of the spark plug. Pull off the spark plug wire and remove the spark plug, using a ratchet fitted with a deep socket. Look for carbon or oil buildup on the spark plug electrode that could prevent sparking. Also, look for a crack in the ceramic insulator. If you see excessive buildup or a crack, replace the spark plug.
If the spark plug looks good, reinstall it and then connect a spark plug tester to check the ignition system. Release the rope from the mower handle so it’s in reach when testing the spark plug. Connect the tester boot to the spark plug and connect the spark plug wire to the other end of the tester. Clamp the bail control bar down to release the blade brake. Pull the starter rope and see if the tester sparks.
If the tester does spark, then the engine could have a fuel or compression problem. Check out this video to troubleshoot those issues.
Stop wire
If the tester doesn’t spark, then you’ll need to check the ignition system.
Disconnect the spark plug tester and leave the spark plug wire disconnected.
Remove the screws from the blower housing and pull it off the engine to access the ignition system.
We’ll check the stop wire first. The stop wire connects the engine stop switch to the ignition coil. It diverts the spark plug current to the metal engine block when you release the bail control bar so the spark plug quits firing and the engine stops. If the stop wire frays and shorts to the engine before connecting to the stop switch, the spark plug will never get electrical current to spark.
The stop wire is difficult to visibly check, so we’ll check for a short in the stop wire using a multimeter. Clamp the bail control bar down to disengage the stop switch. Set your multimeter to measure ohms of resistance. Disconnect the stop wire from the ignition coil and touch one meter probe to the stop wire spade.
Touch the other meter probe to the engine block. The meter should read infinite resistance if the stop wire is intact. If the meter measures resistance or reads 0 ohms, then you’ll need to replace the stop wire.
Plug the stop wire back into the ignition coil if the wire is okay.
Ignition coil
Next we’re going to check the air gap between the ignition coil and the flywheel.
When you pull the starter rope, the ignition coil produces electric current as magnets in the flywheel spin past the ignition coil. The ignition coil won’t produce any current if it’s too far away from the magnets.
Use a feeler gauge to measure the gap between the ignition coil and flywheel. You should measure between.006-inch and.014-inch. Reduce the ignition coil gap if it’s wider than.014-inch. To do this, rotate the flywheel until the magnets are in front of the ignition coil.
Insert the.010-inch feeler gauge leaf. Loosen the mounting screws until the magnets pull the ignition coil against the leaf. Then, tighten the mounting screws. Rotate the flywheel to free the leaf and pull it out.
If the ignition coil gap is correct, then you’ll need to replace the ignition coil because it isn’t sending current to the spark plug. Here’s a video that shows you how.
Flywheel key
If the engine misfires, backfires, sputters or jerks the starter rope out of your hand when you try to start it, the flywheel key could be broken. A broken flywheel key disrupts the ignition timing because the magnets aren’t passing the ignition coil in synchronization with piston movement.
By design, the flywheel key shears off to protect the engine from damage if you hit a rock or tree stump while mowing.
Remove the flywheel and check the flywheel key.
- Tip the mower onto its side with the air filter up and wedge a block of wood between the mower blade and the housing to keep the crankshaft from turning when you loosen the flywheel nut.
- Remove the flywheel nut, washer and recoil starter cup.
- To protect the crankshaft thread, rethread the flywheel nut so it’s flush with the end of the crankshaft.
- Install a flywheel puller on the flywheel.
- Screw the flywheel puller nuts down to lift the flywheel.
- Tap the top of the flywheel with a hammer to break it free from the crankshaft.
- Remove the flywheel puller and flywheel nut.
- Remove the flywheel and check the flywheel key.
Replace the flywheel key if it’s broken. Here’s a video to show you how.
Once you replace the broken flywheel key, the ignition should work and the mower should start.
I hope this video helps you out today. Be sure to check out our other YouTube videos. Subscribe if you like them, and you’ll be among the first to know when we upload new repair videos.
