Tractor running fine --cutting grass. Shut off engine &tried to start. Turns over, have spark to plug,backfires, getting gas to carb, but will not start. Suggestions??

SOURCE: Craftsman 14.5 hp 42

Make sure that you have 12vdc at the carb solenoid. If you do, next check your compression. You can do this with a compression gauge or by taking the spark plug out and placing your thumb over the hole and turning over the engine. If you are building compression it will blow your finger off the hole. If not check your valves to make sure they have the right clearance.

SOURCE: My Craftsman 15.5 hp 42 in deck lawn tractor

Sounds like dirt or water in your fuel system. Have you drained the bowl on the bottom of the carburator? There is a small bolt on the bottom of the bowl; be careful not to over tighten it. If you find anything but fuel in the bowl you may need to drain your tank as well.

SOURCE: Tractor wont start

For a small gas engine than won't start, think FAST -- Fuel, Air, Spark, Timing. You've replaced the filters and spark plugs and squirted in some starter fluid, eliminating the simple common fuel, air, and spark problems -- but I because of the backfiring I think your problem is in the timing -- like a sticking valve. Probably more than you want to tackle at home, but might not be as expensive as an engine replacement. Take it to a good small engine mechanic -- best bet is a lawn equipment shop that has been around many years. Drive a little farther to get to one if necessary.

SOURCE: craftsman tractor model #917271020 backfires but it will not start. Kohler 15.5 engine

suggest to look at the carb adjustement unscrew

Curtis Sewell

• 7482 Answers
• Posted on Mar 23, 2013

SOURCE: John deere la 105 19.5 hp B & S engine. The engine turns over fine, has good blue spark at plug, gas going to carb but won't start. On occasion it will backfire while trying to start. I squirt

Hi Greg..
Your problem is the carb is flooding your plug.
Rebuild/Replace the carb.
To rebuild, follow the instructions below.
Please take time to rate me
Bud
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Sounds like you have dirt/debris in your caburetor jets,fuel passages or a diaphgram that is becoming non-flexible.
Check/Clean/Replace your Air Filter, a dirty air filter can make your engine run to rich with fuel.
Also be sure to check and clean your spark arrestor in the exaust,if you have one installed on your engine.
Note: ALWAYS USE COMPRESSED AIR TO CLEAN YOUR JETS AND PASSAGES, VERY IMPORTANT.
Note:Before you disassemble the carburetor:
Write down on a piece of paper or take a picture of how the linkage attaches to your carburetor for later reference when you go to reinstall your carburetor.
Mark each piece with a awl, or some kind of instrument that will make an alignment scratch before you disassemble the carburetor into separate pieces.
That way you will know which way it goes back together when you reassemble it.
Sometimes you can get by with priming the carburetor or by using a very small shot of starting fluid and letting it run a few times like that, and it will flush the gunk out of the jets,but most of the time you will need to rebuild the carburetor.
Be sure to check your fuel tank for water and dirt/debris, if there is water/debris then you need to clean your tank.
Check you fuel line condition after a while they will degrade and need replacment.
Check/Clean/Replace your fuel filter if you have one, normally they are located in the fuel tank of chainsaws and weedeaters.
When you remove your fuel lines from the carburetor be sure to make a drawing to how the lines are connected to the carburetor or take a pictue for later reference.
Normally the big line will be the line the fuel filter is connected to inside of the tank.The smaller of the two lines is the return to the fuel tank from the carburetor after it is pumped thru the carburetor by the primer bulb.
Make sure you are using fresh fuel...and oil if your using a two cycle chainsaw or weedeater with the oil to the right mixture...too much oil as it can cause hard starting and excessive smoking.
If the chainsaw/trimmer is over a couple of years old, then I recommend that you buy and install a new carburetor repair kit,because the diaphragm will get hard and that will cause it to be hard to crank.
The diaphgram may look good and flexible, but it can be deceiving and not act as a fuel pump as it should because it has become too hard and will cause hard starting,start and run and shut off, etc.
When you clean your carburetor, I recommend that you use a laquer thinner type cleaner to clean and dissolve the laquer build-up in the float and needle jet passages.
Be sure to remove all plastic and rubber parts before using the laquer thinner because it can dissolve the plastic parts and render them unuseable.
Be sure to use COMPRESSED AIR to blow out all the fuel and air passages.The higher air pressure is needed to blow some of the trash/debris from the fuel or air passages.
Be careful when blowing out the passages, because there are sometimes small rubber type seats in the bottom of some of the passages.
Keep in mind that the float (if you have one) for the carburetor must be level when you go to reassemble the carburetor or follow the instructions you get with the carburetor kit, or you could also ask the parts man that you get your kit from.
When you clean your carburetor and remove the jet screws, you will first need to lightly seat the jet screws.
But before you lightly seat the jet screws count the number of turns it takes to seat the jet screws from their original position.
Be sure to mark the turns down on a piece of paper.
That way when you put the jets back in, you know to lightly seat them first and then turn them back out to their original position before you started.
Note:
The little spring inside of the carburetor goes under the float arm.
That is where your fuel inlet needle/float valve is located...on the arm at the end.
Normally there is a small indention in the carburetor base and a small protrusion on the underneath of the float arm where the spring will be in the right postion for installation.
The spring will set in the indention and you will install the float arm with the needle/float valve and float rod into position over top of the spring,you will push down until it is in position and then you can tighten the screw that holds the float arm assembly in position.
Once you have your carburetor cleaned/rebuilt that should solve your problem.
Please take time to rate me
Bud