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Mower Problems


bodad's Avatar
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08-10-08, 10:43 AM   #1  
Mower Problems

I have a JD STX 30, Kohler Command 9HP('89 I believe) Engine that has lost a lot of power this year and now when it gets hot it dies and won't restart until it cools off. First the blade quits turning (electric engages them) then it dies and won't turn over. Battery is good, it had a charging problem with I think some bad wiring that I fixed by running a seperate charge wire, did this before the charge problem and now after. A few weeks back it started bogging down in relatively short grass and lacks power to pull very hard and then it started the dying problem. Other than being weaker and dying when it's hot, it runs smooth, starts right up(first time as well as after it dies then cools off), no issues. Any ideas?

 
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rogerflies's Avatar
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08-10-08, 11:00 PM   #2  
It sounds like you're losing power to the electric clutch and the fuel shutoff solenoid.

You've probably got a bad connection in the electrical wiring or something is amiss in the keyswitch.

I'd replace the fuse first, though.

Once you get the electrical system working again, you can deal with the loss in engine power.

 
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08-11-08, 08:39 AM   #3  
How exactly does the fuel shutoff solenoid work? Is there a way to check to see if the keyswitch is bad? It seems to work otherwise although I did have to gut the upper part of it because I lost the key so I could start it with a screwdriver. Any ideas on the power issue, maybe it's something I could dig into while I have it apart trying to trace down wiring issues.

 
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08-11-08, 10:02 AM   #4  
The fuel shutoff solenoid is pretty simple. When power is applied, the plunger pulls into the coil, and that opens a valve so fuel can flow into the carburetor jets. When power is removed, the valve closes to stop the flow. It keeps the engine from backfiring as unburned fuel/air flows into the muffler, which was very common on small engines before they started using the solenoids. It's also more environmentally friendly.

Did you replace the fuse? Sometimes they wil look OK, but the element will be broken. It can heat up and open the circuit for a short time, then close and work for a while.

You'll need a meter or test light to check for power at various points in the electrical system. Your owner's manual should have a wiring diagram. That'll help a lot.

I'd really concentrate on the electrical system first, since that just might cure the other problem.

 
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08-11-08, 03:09 PM   #5  
The only fuse I am seeing is the one next to the keyswitch but I can't see it getting hot that far away from the engine. Is there a different fuse you're referring to?
It seems to be directly correlated to the temperature, not just a set length of time, for example, I mowed with it for almost an hour the other day but it was only about 83 outside, I tried it the time before that and it was over 100 and it didn't take long to die out on me.
I appreciate the assistance by the way.

 
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08-11-08, 03:58 PM   #6  
What is the little black box about 3/4" x 1" with two posts coming off of it? It mounts near the battery with a hot directly into this and then off this into, I think, the keyswitch. It says 12V25A on it so is it some kind of fuse. The posts are rather rusty and may be losing connection which may be the problem.

 
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08-11-08, 04:24 PM   #7  
A typical fuse and fuseholder looks like these:





If the little box you're looking at only has two wires going to it, it may be a fuse. If it has more than two wires it's probably a relay for the seatswitch circuit. Fuses aren't usually labelled with the voltage, but a relay would be.

Trace the wires. If they go to the seatswitch and the mower blade clutch switch, then it's a safety relay that shuts off the engine if the blade is engaged with the seat up.

I was thinking the fuse would be getting hot because it's not making good electrical contact at the broken spot, not from the hot engine.

The rusty posts make me think you may be looking at the starter solenoid relay, which looks like this:

 
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08-11-08, 08:51 PM   #8  
It looks more like the pic of the starter solenoid relay but I bypass it and hook the wire directly to battery and it still starts so would that still be it? It's right next to the battery under the seat and has a battery hot attached to a post and from there to the keyswitch it looks like. Regardless, I bypassed it and ran the mower a bit today and it didn't seem to make much of a difference of course it's cool today and I didn't have any tall grass to test it out on.

 
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08-13-08, 01:37 PM   #9  
Well I tested the mower out with some heavy grass and a little heat with that black box bypassed (we ever figure out what it is? Would it start with it bypassed if it was the solenoid?) and it never did die. Now this could be a coincidence or maybe it fixed it but regardless, it still seemed to lack power through the thick grass. It seems when you switch the blades on it seems to drag the mower down an inordinate amount.

 
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08-13-08, 02:26 PM   #10  
It can't be the solenoid, because the solenoid cannot be bypassed. If you bypassed it, the starter would run all the time.

It must be some sort of fuse or circuit breaker. I'd sure like to see a picture of it. Does it look like this?


or this?


What happens when you switch the blades on when you're not in grass at all?

Do you have an ampmeter on the mower? What's it showing when you switch on the blade clutch?

You didn't happen to bypass the terminals on the back of the ampmeter, did you?


Last edited by rogerflies; 08-13-08 at 03:04 PM.
 
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08-13-08, 03:55 PM   #11  
The little black box with two terminals next to the battery under the seat is a 12 volt 25 amp circuit breaker. This is like a fuse that replaces it self over and over.

Your lack of power needs more info
How many hours or years of use ?
Does it make any noises or sound like the exhaust leaks ?
Are you trying to cut heavy deep grass at the same rate or speed as normal grass ?

Have you checked the blade quills? Is a blade brake dragging?
Are the quill bearings bad and dragging then transfering the heat to the pto clutch and overheating it?

You said that the key switch is now a screwdriver switch.
Is this thing left out in the weather?
Did you leave the bad wire that you "bypassed" hooked up?
Are you sure that it is charging properly?
The pto clutch draw a lot of amps and more when it gets hot.

I suggest these becuase I had a tractor with a dragging brake, two with bad quill brgs, and now one that ran with a blow head gasket that sounded like an exh leak. All came with your story.

Hope it helps

 
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08-13-08, 07:43 PM   #12  
From what you write, it appears you have more than one problem with your mower and there is confusion with parts terminology and location.

To clear up parts terminology and location here is a link to JD‘s parts look up. Enter model as STX30 that is with no spaces.

http://jdpc.deere.com/jdpc/servlet/c...ageServlet_Alt

Are you sure about your engine being a 9HP Kohler Command? What is the model and spec number of your engine?

Download a free Kohler engine manual at:
http://www.kohlerengines.com/service/manuals/index.jsp

Bodad said, “Engine that has lost a lot of power this year and now when it gets hot it dies and won't restart until it cools off.”

A leakdown test while engine is hot will identify areas causing loss of compression, which would cause power loss. I suggest you adjust valves as a minimum. To correctly diagnose power loss a leakdown test should be accomplished. Links below will explain what a leakdown test does and how to make a tester if you do not want to buy one.

http://en.wikipedia.org/wiki/Leak-down_tester

http://www.xs11.com/tips/misc/misc3.shtml

Bodad said, “First the blade quits turning (electric engages them) then it dies and won't turn over.”

Could you make this statement more clear? Is the electric PTO disengaging? Can you not use the switch to reengage the PTO?

 
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08-13-08, 08:57 PM   #13  
What circuit is the one amp fuse (item 14 on the wiring harness parts diagram) next to the keyswitch used for? The only thing that makes sense is for it to provide power to the fuel shutoff solenoid. Is that it?

 
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