Mower Hard to Start When Hot
So what's wrong with a mower that's hard to start when hot? Hard hot starting mower issue is most likely caused by a failing coil, but there are other possibilities:
- Plug faulty
- Engine flooded
- Low oil level
- Engine overheating
- Plug wire faulty
- Auto choke faulty
- Carburetor faulty
- Valve fault
Check The Oil Level
Check The Spark Plug
Spark plug is the most likely cause of a hot starting problem and is the easiest problem to solve.
A new spark plug should be fitted at the start of every season.
What Is A Coil?
How a Coil Works
The Coil & Plug Test
If you have no spark or it's poor, you may have a faulty: Spark plug wire; Plug cap: Bail lever cable: Short circuit of coil control wire: Coil damage. If your spark is good and the problem still persists, then check out "carburetor cleaning".
Plug wire damage can be caused by old age, mice or chafing off the mower body.
If all looks OK move on and check the bail lever and switch.
Ordering a coil on-line is easy but you will need your engine number.
Although all coils look the same, they're not.
Engine May Be Overheating
Low Oil Level
Is It A Mechanical Failure?
Is It Getting Fuel
Some automatic choke systems are prone to over fueling when hot starting.
If your mower has a priming bulb this test does not apply. An engine fitted with a priming bulb type choke that's hard to start hot, and is Smokey - will likely need the carburetor to be cleaned or replaced.
To test choke plate type, remove the air filter. Here I have removed the complete air filter housing for demo purposes.
When throttle is set to run - choke plate should be open. Often a choke plate may be partly closed even though the throttle lever is set to run, adjusted cable.
Your mower may not have a choke lever, you may have auto choke, this test will still apply. Check the choke plate when hot, it should be open. If not check for binding in the linkages / failed thermostat.
The choke plate in the closed (on position). This is the correct position for starting a cold engine.
Check that the choke closes fully when choke lever operated, if not adjust cable. If you have the auto choke system - the choke plate should be in the closed position as per picture when engine is cold.
If not check for binding or fault with the thermostat choke control unit - fitted against the muffler.
It's also quite common for carburetors to fail, causing either too much or too little fuel. Cleaning the carburetor is always a good plan, and if this doesn't help, replace it.
Replacement Briggs & Stratton carburetors are inexpensive and easy to fit.
How do you fix a mower that overheats? Remove the engine cover, and using a hand brush or compressed air remove the dry grass clippings from the engine cooling fins. Check also that you're using the correct gas, regular gas is best for small engines, e10 is OK but e15 or e85 will cause the engine to overheat.
Lawn mower won't start oil on spark plug? The most common reason for oil on a mower spark plug is too much oil in the engine, but there are other possible causes:
- Mower turned on its side
- Head gasket failure
- 2 Cycle gas used
- Engine worn out