It is a common problem when you want to start your old lawnmower, but even new gas and new oil don’t make you happy. I’ll show you several reasons and how to fix them. Of course, I’ll get some info for riding mowers too.
Three Most Common Problems When Lawn Mower Doesn’t Start
I’m going to show you the three things I had to do to get my push mower to start after sitting for three years.
Problem №1. The Old Spark Plug
The first thing you should remove the old spark plug requires a 5/8 deep well socket. It’s located in the front of the lawnmower, and you can break it loose.
After I’m replacing it with the RC12YC Champion brand, I’m sure there are other brands, but this is the one that I chose. Moreover, read the instruction because maybe the manufacturer recommends a special one. I put it in hand tight first.
Then I take my a ratchet, and now you don’t want to over-tighten this. You want to snug it up. Just snug it up. Do not overtighten that. You’ll break it off.
Did the replacement and still doesn’t work?
Problem №2. Air Filter
The next thing you have to do: check the air filter. It can be nasty with oil stains and dust. The maintenance of the air filter should be done every year. So, replace the filter with the new one, and that’s it!
Problem №3. The Dirty Carburetor
To get to the carburetor, you need to remove these two bolts (see the photo below). American Standard, they’re 5/16, in metric, they’re 8 millimeters. I’d say use either a standard 5/16 socket or use 8 millimeters.
This hose comes off of here, right there. Those two there, you got your carburetor right here. Be careful with this gasket, or you’ll have to get another one. Now, you could take the carburetor off with these two bolts and clean it up real good, soak it maybe.
You could take the whole carb off and soak it or spray it down real good and clean it real good. I’ve just tried spraying it because I don’t think it’s in that bad shape. So I just sprayed it right in here, and I’m going to put everything back together and try to crank it back up.
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So, hook the hose back up. Don’t forget to hook the hose back up. And when you put this back on, don’t mess up the gasket. When it’s done, try to start your engine, and I think you will get success for your patience.
If you want to know more about repairing lawnmowers and other machines, I strongly recommend Comprehensive Small-Engine Repair Instruction.
Other problems with the lawnmower
Check the Fuel First
It’s a simple solution, but have you checked the fuel? Maybe there’s a leak. To check, you’ll need to check the gas tank. If there is a leak, then you can find a replacement tank online for much less than taking it to a shop—more information you can in my article about gas for the lawnmower.
Mower Battery Dead
If the gas tank isn’t the issue, then the next step is to check the battery. Is it old or damaged? You can use a multimeter to check and see if it’s completely dead.
Dirty Spark Plugs and Belt
You can use carburetor cleaner to clean your spark plugs if you suspect that they are clogged with dirt and residue.
Loss of Power
Does your lawnmower start spitting and then stop? One of the causes is a dirty filter. Your lawn mower manual can show you where the filter is and how to clean it. If it’s too dirty, consider just ordering a replacement.
In other cases, the spark plugs may be the issue. These need to be cleaned every so often, but you can also replace poor spark plugs that always seem loose or the root cause of the problem.
Starter Rope Won’t Pull.
When a starter rope won’t pull or seems too hard to get started, then you likely have an issue with the engine flywheel brake. This is the bar that you typically hold down on the handle that halts the engine when let go. You should make sure that the bar is completely lowered before pulling.
If your mower blades are compacted with grass and clippings, then you may also have a hard time pulling the starter rope. In this case, you’ll need to turn the mower over and clean out the debris.
Smoke Coming From Lawn Mower
When a lawnmower smokes, the most common issue is a full oil chamber or an oil leak on the exhaust, which causes smoke if the mower is tilted just slightly. However, if you see the light or white smoke, and your mower won’t keep power, then it may be a more complicated matter with your engine.
To find out what the issue is, you’ll need to examine the oil chamber and spot any leaks. Please note the lawnmower must be completely turned off and cooled down before checking the oil chamber.
In some cases, your oil cap may just have been loose, but if neither of these seems to be the problem, then you should take it to a professional shop. There is likely a more significant problem at work here, and any further use could damage your mower irrevocably or cause harm to yourself.
Slower Lawn Mowing Speed
Over time, your drive belt can suffer damage or even become dislocated, thus causing your mower to slow down. You can find the drive belt within the motor casing area, or you may want to check your mower’s manual to see where it’s located.
After turning off the mower, check that there is no damage to the drive belt and that it’s firmly attached. If damaged, it’s easy to order this part online and replace it at home.
However, if you have a battery-operated mower, it could just be that your battery needs to be replaced. You may want to use a multimeter to check the status of the cell.
A significant problem for older lawn mowers is the carburetor. Over time, this part can become corroded and cause the lawnmower to stop working. In these cases, you may need to replace the carburetor altogether.
Sometimes a plugged fuel filter can be mistaken for a carburetor issue. If there is a clog, you’ll need to consult your owner’s manual to locate the fuel filter and check the fuel lines to the carburetor.
Lawn Mower Blade Problems
Did you accidentally go over a tree root or rock that bent your blades? Chipped, bent, corroded, and otherwise damaged blades lean-to unusual mulching, vibrations, or a stalled mower. The best way to determine the issue is to turn the mower over and inspect each blade for problems.
If your mower is protected under warranty, you may be able to get a replacement blade. Otherwise, you can order these parts online and fix them at home with a few tools.
Quick Summary of Lawnmower Troubleshooting
Before you kick your loyal grass-cutter to the curb, you can use the following tips to isolate most of the issues with your lawnmower.
- Check gas, filter, and fuel lines first to ensure there are no clogs or debris.
- Look up lawn mower parts in the manual first before replacing them
- Always follow your owner’s manual when changing the oil or replacing parts
- Make sure you use the right type of fuel
- Clean out the underside of your mower after each use
- If using a battery-operated lawnmower, test the battery with a multimeter if experiencing power problems
- If you see light-colored or white smoke from your mower, shut it off and take it to a shop
The Most Common Problems With Riding Lawn Mowers
1) The Engine Won’t Turn Over
This is a widespread issue to run into, especially if your mower has been left idle for an extended period of time.
Start by checking all of the safety features of the mower for proper operation. Sit on the mower and confirm that the parking brake is on and the mowing deck isn’t engaged. Make sure you’re toggling all of the safety switches as directed by your operator’s manual.
If you don’t have an issue with the safety features, your next likely culprit is the battery. Battery cables can occasionally pop off the battery’s terminals. If you find this is the case, reconnect them securely before trying to start the mower again. Remember that the black negative cable must be attached to the battery’s negative terminal, which should be marked with “NEG,” “-, “or “N.” The red positive cable needs to be attached to the battery’s positive terminal, which will be marked “POS,” “+,” or “P.”
After you’ve checked the battery, look at the fuses next. Check your operator’s manual to make sure you inspect all of the mower’s fuses; they may be located in different areas. Replace any blown fuses with new automotive fuses that match their amperage.
Finally, locate the engine’s ground wire and confirm that it’s in proper working order. The ground wire should lead from the engine to either an unpainted patch of the mower’s frame or a mounting bolt.
2) The Engine Turns Over But Will Not Catch
If you can bring your riding mower close to life but not actually engage the engine, a lack of fuel is likely the problem. You need to have a full fuel tank, a fueled carburetor, and a clear fuel line. If you determine that you have a clogged line, clean it out and install a new fuel filter.
The engine will not start unless the mower’s throttle and/or choke set correctly. Double-check the appropriate settings in your owner’s manual; the right settings vary from model to model.
If the controls are set correctly and fuel your problem, your problem may be a faulty spark plug. You can check this using a spark plug tester. Check each plug’s seating and clean its cap. Any spark plugs which still will not work should be replaced.
3) The Mower Smokes When The Engine Is Running
This alarming-looking problem is typically caused by having excess engine oil in the system. It should resolve itself once the excess is burned off; you can hurry this process along by checking your mower’s oil level and draining off oil.
If your mower’s oil level is within the proper marks and the engine is still smoking, and you might have a crack or break somewhere in the system, which is making it impossible to seal the crankcase fully. This can happen if you have a breakage or defect in a valve cover, dipstick tube, dipstick, engine breather assembly, or other vital parts. Assess the parts’ condition carefully and replace broken ones; this should restore the crankcase to full working order.
4) Constant / Excessive Vibration
Violent vibrations are typically caused by damage to a mower’s spindles, pulleys, or blades. These issues are typically caused by running them over a solid object, damaging them, and spoiling their alignment. Mowing over rocks, roots, and sewer outlets can all cause this type of damage. Any parts showing evidence of this type of damage need to be replaced.
Loosened or absent mounting bolts might also cause excessive vibrations, a cutting deck set at the wrong height, or idling the engine at low RPMs. You should also check the machine for damaged or twisted belts. Check the seating of all belts and replace any that show evidence of wear and tear.
5) Poor Performance With Discharging, Bagging, or Mulching
If your mower isn’t getting rid of cut grass the way it’s supposed to, there are several potential problems to check for. First, verify that you’re running the engine at full throttle; the discharging, bagging, or mulching functions will not work at full efficiency at low RPMs.
Take a close look at the set of the mowing deck. It should be level all the way across the mower’s width, while the front end of the deck should be slightly lower (3/8″) than the rear.
Finally, you should take a look at the condition of your mower blades. If they are dull, they could be delivering unsatisfactory results. Sharpen or replace them as necessary.
Be aware that adverse conditions may impede your mower’s functions. Running it over grass that’s wet or too tall will reduce its effectiveness.
6) The Mower’s Blades Don’t Engage In Reverse
This may not be a technical problem at all. Before 2005, mowing in reverse was made impossible as a safety feature. Newer mowers may have this capability, though. Check your owner’s manual for reverse mowing information and instructions.
7) The Tractor Is Still In Gear In Neutral
If your mower refuses to move while you have it in neutral, the transmission relief valve is probably not set correctly. The mower’s brake may also be sticking. Check the owner’s manual to confirm that you have the relief valve set in the right position.