Craftsman Lawn Tractor cranks, will not start...

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  #1  
Old 05-25-14, 05:46 PM
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Craftsman Lawn Tractor cranks, will not start...

Good Evening all.

I have a few years old Craftsman DYT4000 Lawn Tractor (model number 917.275630) with a B&S 18.5 HP single cylinder OHV Intek Plus motor. Here's my problem:

The motor will crank, but will not fire, sputter, start, nothing. Here's what I've done so far:
  • charged battery; holds charge well
  • Replaced the fuel filter
  • Installed a new spark plug
  • Installed new ignition coil/magneto; placed a business card away from flywheel.
  • removed flywheel and inspected flywheel key; no shearing and appeared ok.
  • removed & cleaned carb & bowl
  • checked and cleaned air filter
  • checked fuse (ok)
  • emptied all fuel from tank, put new (purchased today) fuel in tank
  • replaced fuel line from tank to new fuel filter (line was collapsed near tank)
  • replaced fuel line from fuel pump to carb
  • tested compression by removing the spark plug and covering hole with my finger while engine was cranked; compression appeared strong
  • tested new spark plug for spark; passed (spark observed when s.p. is out of hole and near frame or motor.
  • did not observe any wires shorted out (from what I could see)

Fuel is making it to the newly-cleaned carb. Engine is cranking without anyone in seat, but will not crank at all unless brake is depressed (as I believe it is supposed to be)... For the life of me, I can't figure out why the mower will crank, but not fire up. The spark plug is dry when I pull it after all the above tests. After cranking for a while, the carb does flood.

Any help is appreciated; THANKS!!!!
 
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  #2  
Old 05-25-14, 06:00 PM
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Go to the coil and disconnect the small wire from the harness, leaving the spark plug wire hooked up. Then check for spark and if good put the plug back in it and see if it will start. Keep in mind you'll have to choke it to kill it. The small wire is the kill wire.
 
  #3  
Old 05-25-14, 06:53 PM
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Thanks for the suggestion. Yes, there was spark, no, it did not start.
 
  #4  
Old 05-25-14, 07:11 PM
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With spark, pull the plug, shut off all gas to the carb. Then spin it over about ten times with full throttle, no choke to purge the cylinder. Then put a teaspoon of gas directly into the plug hole, install the plug and with half throttle, no choke and the gas still shut off see if it will fire. YOu'll have to spin it over a few times.

If it fires, then dies, turn the gas back on to the carb and see if it will start and run.
 
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Old 05-27-14, 04:10 PM
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marbobj,

Did as instructed, and received a backfire but no sputter.

Turned the gas back on (well, reattached the gas line as there is no shut off), and attempted to start it normally; received no sputter or backfire, just cranking.
 
  #6  
Old 05-27-14, 04:32 PM
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It sounds like an engine that's flooded. Keep all gas out of the carb except the prime you feed through the plug hole. Use full throttle and no choke. If you get a response from the engine spin it a few more times, then hand feed it again. You should get a short run time off the hand feed.

Also check the oil for a gassy smell. If there is change the oil before trying to start it. The gas fumes from the crankcase will add to the flooded condition.
 
  #7  
Old 05-28-14, 10:47 AM
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I got another backfire, and that's it. The oil does not smell like gas, so I didn't do the oil change (level is fine on the dip stick). I next pulled the plug and cranked it until I did not see any gas mist coming from the sp hole, then tried it again: about a tea spoon of gas in the hole, put the plug back in, full throttle, no choke, and cranked... no luck. I'd even emptied the fuel out of the carb bowl before the backfire.

I thought that maybe there was not enough gas. Hooked it all back up again, and still would not start. Didn't crank that long (maybe 20 seconds twice), and didn't smell gas, so I don't think it's flooded any longer...
 
  #8  
Old 05-28-14, 10:55 AM
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Is this the first start of the year (or first start for you). Was it running and then stopped or didn't start with the present problems. Is the back fire out of the exhaust or the intake/carb?
 
  #9  
Old 05-28-14, 11:55 AM
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I'm in Naples, FL; there is no real "first start of the year" haha... but, the last time I used it was about 3 weeks ago. It had developed (over the last 6 months or so) a habit of not turning over right away, but I attributed it to low volts. It always started and then would run fine; would take about 8 to 10 seconds to start while cranking. Every once in a while it would backfire on shut down. Last week I tried to start it but the battery had died. I charged it and it cranked w/out problem, but has not yet started.
 
  #10  
Old 05-28-14, 02:40 PM
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Also, I believe it backfired through the intake. I wasn't really paying attention, but it was louder up front.
 
  #11  
Old 05-28-14, 03:39 PM
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A lot of what you have falls under the heading of symptoms of flooded engine along with some things in the carb getting progressively worse. However, when you prime the engine through the plug hole with the vapors purged from the cylinder, and all other things in good shape, they usually try to start. From there it's a matter of fixing whatever problems you may have with the fuel system.

The backfiring after shutdown is usually caused by fuel in the exhaust put there by the after run of ignition shutoff. Some engines have fuel shutoff solenoids for that and control the backfire.

A backfire through the intake can be caused by flooding, but with a no start with the priming you would have to look at the exhaust valve not opening like it should and the compression in the cylinder blowing back through the intake valve when it opens.

You may have an exhaust valve cam lobe wearing down or simply valve clearances out of adjustment. You would need to take off the head and watch the movement (opening and closing of the valves) to determine if that is what is happening and either adjust the valve clearances (if adjustable) or have additional engine work done.
 
  #12  
Old 06-01-14, 10:18 AM
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SOLVED!

Flooded? Yes, but that was because the intake valve was "soft" locked up and the fuel was not making it to the spark plug. After spending another morning with the tractor and a friend that used to work on them, we initially thought the valve was frozen in place (when looking in through the intake manifold). At that point we thought we couldn't hurt it any more and pulled off the valve cover. Good thing we did; I was about to junk the motor.

The intake valve rocker was not seated on the intake valve, and the related push rod was bent. Therefore, a simple replacement of the $15 pushrod and readjusting of the valves solved the entire problem.

Thanks for the help with this!
 
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