Riding mower won't start.

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  #1  
Old 05-19-14, 05:26 AM
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Riding mower won't start.

Hi all,

I was given a riding mower recently by my father-in-law. He said it ran fine all last year aside from some oil leaking from the valve cover (fixed). This year, it had some trouble starting. While reading through the forums, and watching some videos, my guess is the starter can't overcome compression in the cylinder.

When I turn the key, the shroud/cover spins a few degrees, then stops, repeats a few times...and then once in a while spins about half a turn. This goes on for a few seconds before turn the key back to off.

I pulled the spark plug, and noticed I could rotate the engine (by hand) easier with the plug out. I moved it to TDC and checked the valve clearances and got 0.004". This seems dead-on from what I've read. (Lucky me because I can't find a set of crowfoot wrenches).

Am I missing something?

Engine stats:
Tecumseh OHV17 (17hp)
displacement: 490
There were some more numbers on there, but I'm not sure what they're for (see pic below)

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Any help is appreciated.

Matt
 
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  #2  
Old 05-19-14, 05:52 AM
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Check the spark by grounding a spark plug to the engine. You should get a bright blue spark. (It's easier to see in a dark garage, etc. If you're good there....

Make sure your battery is up to charge. If not charge it or jump start the mower with a little gas down the plug hole. Then half throttle, no choke, spin it over.
 
  #3  
Old 05-20-14, 06:09 PM
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Update

I pulled the plug, cleaned it and tested it, but got no spark. I installed a new one and recharged the battery.

The starter spins better than before, but nothing happens after that. Everything sounds normal, and it seems like everything is kicking in.

Should I clean the carburetor?

Matt
 
  #4  
Old 05-20-14, 06:28 PM
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You may need to Matt, but the first thing is getting a spark.

Did you get a spark with the new plug grounding it to the engine? If not, and make sure the grounding point on the engine is clean, find the ignition module/coil. You can find it by following the plug wire back to the coil. There is a grounding wire (small wire) attached to the coil/module. Disconnect that wire from the wiring harness that would lead to safety switches/ ignition switch, etc. Then check for spark again. If no spark you may have to replace the coil.
 
  #5  
Old 05-20-14, 06:32 PM
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Got spark

Sorry marbobj,

I did get a spark, I just realized the way I wrote my last post was a bit open-ended. The first plug did not, but the new one worked fine.

Matt
 
  #6  
Old 05-20-14, 06:38 PM
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That's fine. Better to have a good module than having to buy another one.

Take the spark plug out, tie back the plug wire to avoid a fire from arcing. With the throttle open full, the choke off and all fuel cut off to the carb and the carb bowl empty, spin it over about ten times.

Then add a tablespoon of gas to the plug hole and with full throttle, no choke and the plug installed see if it will fire. If it tries to start, put it all back together, turn the gas on and with half throttle/ half choke see if it will take off and run.

If you got it to start on the prime through the plug hole, but it won't run, then pull off the carb and clean it.
 
  #7  
Old 05-20-14, 06:43 PM
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Ok that sounds good. I'll get to it over the next week or two. I won't have much time in the near future.

Now, when you say throttle open full, but not choked, does that mean almost all the way to the top in this pic. (I assume you want me on the rabbit???) Note, this is not my mower, but it illustrates my question well.

http://img177.imageshack.us/img177/6915/22364311go6.jpg
 
  #8  
Old 05-20-14, 08:14 PM
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It would be the engine at its fastest speed or the carburetor throttle plate wide open. It's done to vent out the old gas fumes from the engine.

Some mowers may have a throttle lever to set the engine speed and another for the hydro transmission. You want to open the throttle for the engine.
 
  #9  
Old 05-20-14, 10:05 PM
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Sounds to me like you need to adjust the valves to get the engine turning past the compression stroke.
 
  #10  
Old 05-21-14, 06:16 AM
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The Tecumseh manual says that the OHV17 uses a Walbro LMT carburetor so if you need to clean the carb, this may help. Your valve clearance specs. are correct. Just make sure your measurements are since it does sound like the motor is not getting its compression release.

Disassembly, Cleaning and Repair of Walbro LMK Carburetor used on Kohler Command and Courage Single.
 
  #11  
Old 05-21-14, 06:32 AM
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Yep, the .004 is. Is that an engine that uses the 1/4 past TDC to move the compression release out of the way- thinking the.004 clearances aren't good at TDC.
 
  #12  
Old 05-21-14, 08:34 AM
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The Tecumseh manual says to check the valves at TDC, but after the compression stroke. No mention of 1/4" past TDC.

He might want to verify that he measured it at TDC after the compression stroke and not after the exhaust stroke. If the latter, there is not much time between the exhaust closing and the intake opening, and that could create a measurement error.
 
  #13  
Old 05-21-14, 09:13 AM
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I didn't read slowly enough and skimmed over the part about the valves already being adjusted.

Still, I would suspect a problem with the valve adjustments.
 
  #14  
Old 05-21-14, 09:57 AM
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Me too. If I were him I might check them again.
 
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