Step 5: Install New Spark Plug
Install the new spark plug in the hole by hand, turning it to the right (clockwise). It should screw in easily. Don’t force the plug, since it can cause cross threading. Instead, unscrew the plug and try inserting it again.
Once the plug has been screwed in by hand, GENTLY tighten it with the wrench until snug. Don’t over tighten the spark plug, since it can cause the threads to strip or break the ceramic plug.
Following your instructions, I changed my mower’s sparkplug. (Good, clear instructions!) It started easily and ran normally. The next time I needed to mow, it wouldn’t start and sounded like it did before changing the spark plug. Thinking I might have made a mistake with the plug, I replaced it with a new one. It started right up and ran normally. Couple of weeks later, same story. I have now used 4 plugs this season. Am I doing something that causes the plugs to have shorter lives? Thanks!
Hi Judy,
Your question has been answered on our website at Problem with Lawn Mower Engine Running Rough. Hope that helps!
The article on changing spark plugs was excellent– it was clear, easy to follow, easy to understand. Most important, it took the fear of attempting to do a mechanical repair away! I have compleat confidence I will be able to to other maintenance jobs as well to start up my riding lawn mower in a properly maintained manner. I purchased it last year with 11 hours on it, but want to make sure it is in good shape before I start up. Thanks for the great articles Jackie Shepard.
Hi Jackie,
Thanks for the feedback, glad to hear that our article was helpful!
Fantastic! Now, even I, who has mo mechanical talent can do this thanks to you.
Thank you so much for these instructions! You’ve made it possible for me to fix my mower, while my husband is out of town!
response to judy S.
Judy S. Says:
July 23rd, 2011 at 7:03 pm
Following your instructions, I changed my mower’s sparkplug. (Good, clear instructions!) It started easily and ran normally. The next time I needed to mow, it wouldn’t start and sounded like it did before changing the spark plug. Thinking I might have made a mistake with the plug, I replaced it with a new one. It started right up and ran normally. Couple of weeks later, same story. I have now used 4 plugs this season. Am I doing something that causes the plugs to have shorter lives? Thanks!
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hi judy. i think you have a problem with step 5…tightening the spark plug. most plugs need to be tightened very snugly and it is hard to do with a small tool like in the pictures here. i recommend one quarter to almost one half turn after it is contacted the motor and is very finger tight. now is the time to use a wrench to turn it the extra quarter turn i previously mentioned. of course if it was stuck on some rust and not yet fully seated it will turn more til it is very tight and does not allow the combustion gases to escape which makes your mower not start or run horrible. good luck 🙂
Hi! My husband bought a new mower, put in the oil and gas, then started it but it didn’t start. He then realized it had no spark plug in it. He went out and bought the right one, put it in, and it still won’t start. Is it ruined? Any suggestions?
Rebecca,
That shouldn’t have damaged the mower. Make sure you have the right plug for the mower, and the spark gap is set to the correct distance.
Do I have to unplug the battery so I won’t get a shock?
My loan mower will start for a few seconds and than stop?
I have a powerforce mower and for the life of me, I can’t find the spark plug!!! Do you know whereabouts on the mower it is? Had the hood off and can’t see it.
I changed the spark plug on my old mower without problem, but now I have a mower I bought last summer and it has a very long snug boot that I can’t get off my spark plug. Needle nose pliers get no grip at all on the boot and the boot is so deep that I can’t get my fingers or a screwdriver to the end of it to pull it off. How can I get to my spark plug???
First time trying to do this. There was inadequate warning about the tightening of the spark plug,and I tightened it too much, and wrecked the pin thingy on end of plug!!
I took my lawnmower out today for the first time this season. I put new gas in and checked the oil, but still it didn’t start. I took out me booklet on the lawnmower and it said to change the spark plug. I know where it is and how to get to it, but how long do they last? I had it checked out last year where I purchased it and they said they did it. How short of life does one spark plug have??? Thanks Lots
I can change my spark plug easily but even though the plug is tightened, it pops out when I start my mower. I confirmed the spark plug is the correct size/number per manufacturer instructions. I tried the old one and the new one, they all pop out when I start the mower. Can the housing thread be stripped and if so, how do I fix that?
My lawn mower won’t start even i changed the spark plug. Guess what i used the wrong spark plug for it. Read you article and followed it. Now my issue is fixed. Thanks