Lawn tractor won't start/run when hot

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  #1  
Old 04-06-05, 06:14 AM
koz
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Lawn tractor won't start/run when hot

Hello:

I have a 1983 16hp simpicity lawn tractor that is giving me a headache.
It will run fine for about an hour, but if I stop it after this period of time, it will not start again untill it cools off for 1/2 hour or so. I have good spark on boths plugs. Seems like it isn't getting fuel when it gets hot. ? Any ideas will be greatly appreciated. My neighbor thinks it might be vapor lock...
please let me know.

koz
 
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  #2  
Old 04-06-05, 07:35 AM
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What brand and particularly what engine numbers do you have? Most hot-restart problems are better diagnosed knowing this as different engines have possible notorious problems. Generally though, this problem is either ignition or fuel related. You said you had good spark, but do you have sufficient spark at the moment it exibits the problem? Are your cooling fins plugged with grass debris causing it to overheat?
 
  #3  
Old 04-06-05, 09:50 AM
koz
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The engine is a Briggs & stratton. I will email the model # after lunch.

I cleaned the engine and degreased it last year - when this problem first started. When it would not start yesterday, I pulled the plugs right away, and I had good spark. I had replaced the sending unit on the magnetron 2 years ago, when I could not get any spark, and it ran fine untill last fall.

koz
 
  #4  
Old 04-06-05, 02:44 PM
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If you would please, post the model number her rather than e-mail...so other can benefit from this.
 
  #5  
Old 04-06-05, 09:35 PM
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Since you said "plugs", I guess this '83 engine is a twin, rather than the single that was used years ago. With no further info than we have so far, I would be quick to say the coil is bad. I just today replaced a coil on a '85 16hp briggs that had the same symptoms. good spark, but wouldn't start when hot. Fuel was fine, had to be coil. Replaced it and problem solved. Sometimes the coils break down inside, allowing a spark, but not at the correct time. The heat causes expansion in the coil and lets the problem exhibit itself. but when it cools, the bad connection contracts enough to make good connection again.
 
  #6  
Old 04-08-05, 12:43 PM
koz
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more problems..

Cheese:

You are correct. It's the cast iron twin. I replaced the coil a couple of years ago, and it ran fine after I changed it out, but I guess the coil can go bad inside. I will have to check this out after I fix my new problem... My carb
went bad. I went out to start it, and it threw gas all over the place...gas came out the exhaust, and a good amount is in the crankcase too. I went and got a rebuild kit, so I will have to do this first. Will let you know...
Koz
 
  #7  
Old 04-09-05, 12:42 AM
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Ok, with that info, I would agree with repairing the carb first. If this engine has a fuel pump rather than gravity feed, and the carb is leaking, it could flood the engine when you shut it off. It would flood until the fuel line above the float level was drained. This would make it hard to start for a little while, maybe about long enough for it to cool off. It's a possibility, but I still lean towards the coil. If you determine the coil to be bad, remove the tin covers from the undersides of the cylinders and clean out any debris under them. Your engine may be getting a bit too hot. (even if it's not the coil, these should periodically be removed and cleaned out).
 
  #8  
Old 04-13-05, 10:24 AM
koz
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O. K . Cheese: I rebuilt the carb - and while I was at it, I changed the fuel line, which was cracking and peeling. I had totally cleaned the engine,( including the area under the tin.) I put in a new fuel filter, and plugs also.
I had to jump start the tractor, as the battery was dead. It started right up, and surpisingly, needed almost no adjustments to idle speed. I had my son run it around the yard for 15 minutes. I turned the engine off. I went to restart it, and the battery was dead. ( Why didn't it charge? ) Tried to jump start again, but it would not go. Waited 1/2 hour for engine to cool, and it restarted. - 2 questions. Does this still sound like the coil? 2. Is the dead battery related? My neighbor said I might be cooking my batteries , i.e. too much voltage going back to the battery, so I will put my voltmeter on it once I get it running, and this should tell me if I am charging too much.
any ideas will help.

Thanks, KOZ
 
  #9  
Old 04-14-05, 12:59 AM
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Wierd stuff. Any chance there may have been mice nesting under the blower shroud during the winter months? Maybe some bad wiring under there? Check the battery voltage. If the battery is 2 yrs or older, then it might just be time for a new one. Also, check the kill wire coming from the coil to see if it might be chaffed and shorting somewhere under the shroud. (you have to remove it anyway to replace the coil, if needed).
 
  #10  
Old 04-14-05, 07:06 AM
koz
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Hi Cheese:
No Mice under the hood. Battery is brand new. I had this problem last fall.
I had bought a cheap battery, and it went dead, and would not charge or was not getting a charge. I took it back to the place I bought it from, and they told me the battery was bad,so I got my money back. I went and bought a more exspensive battery 2 weeks ago, from another place, and now I am having the same problem. I am just wondering if I have 1 problem ( the coil? ) that is causeing it not to start when hot and not charging the battery, or if I have 2 problems - Igintion and possibley altenator?? Or voltage regulator?? Anyone else ever had both problems at the same time?

koz
 
  #11  
Old 04-15-05, 01:17 AM
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Well, the coil has nothing to do with the charging system. It sure sounds like something has gotten under the cover of the engine and chewed up or corroded some wires. Look for the charging plug on the side of the engine. Should be at least 12 volts on it when the engine is running with that wire disconnected. It may have a blown diode, letting the battery drain by backfeeding, or if the diode blew open, then the battery just won't charge. Did you get a voltage reading from the battery with the engine running full throttle?

Also, to be sure I'm on the same page, when you have the no-start-when-hot problem, does the engine spin fine, but just won't start? Or, does the starter not even sping the engine well? The recent post you made about it not starting with jumper cables makes me wonder. That sounds like a totally different problem than the possible coil issue we're discussing.
 
  #12  
Old 04-15-05, 06:19 AM
koz
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Thanks again for the reply cheese.

When the engine is hot, and I jump start the engine, the engine spins, but will not fire up. It has spark, but it almost appears to the eye, that the spark is weak and possibliy intermitent. ( back to a bad coil?). I was looking through the engine schematics last night and came across the diode, and circled it. I will look at this as a possible cause.
I will check for 12 volts at the charging plug, as you suggest. Will also check at the battery. This should give me some idea about the charging unit. Will let you know. To me it sounds like 2 issues - coil and diode.

Thanks for the help - Will report back on Monday.

Koz
 
  #13  
Old 04-15-05, 09:09 PM
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no go tractor

loosen the gas cap The vent isn't working. If that works buy a new cap--cheez!


S/T
 
  #14  
Old 04-15-05, 09:17 PM
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no go

only other possibility is ignition switch--trust me--or there is a relay in the circuit that is hooped--usually near the steering column under the hood--when you unplug the relay you will see burnt contacts. If so -replace relay (4 $)

S/T
 
  #15  
Old 05-09-05, 10:01 AM
koz
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Updated info...

Hi Cheese:

I finally got around to working on the lawn tractor again this weekend. I unplugged the charging plug, as you suggested, and while the engine was running, I put my voltmeter on the contacts. I am getting 20 volts! Would this mean the diode is blown,( or a voltage regulator) ? This would explain why I keep burning up batteries! I am waiting for a reply, but it looks like I will need to pull the flywheel to get at the diode. I have a sterring wheel puller, and I am wondering if there are any "tricks" to pulling off the flywheel.

I also broke the contact off of the fuel solenoid, (made a temp fix) and will
need to replace that too!

Looking forward to a reply,
koz
 
  #16  
Old 05-10-05, 01:30 AM
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Reconnect the plug and start it again, checking voltage at the battery. The voltage reading you got will drop when you connect it to the battery, but we need to know how much. Also, on that wire you checked is a diode. It is a lump in the wire covered with black shrink wrap. Use an ohmmeter to check it. You should get continuity across it with the ohmmeter wires one way, but switch polarity and there should be no continuity. If you have continuity both ways, the diode is blown.

Flywheel removal is not required to replace the diode.
 
  #17  
Old 05-10-05, 12:52 PM
koz
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Hi Cheese;

I did what you asked me to do. I am getting 16.5 volts at the battery terminals. I found the diode and checked it ( right where you said it would be). Results were 3,800 ohms one way, and when I reversed polarity, it was infinite. Now what?

Please advise;

Koz
 
  #18  
Old 05-11-05, 12:29 AM
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From your test results, the diode is fine, the charging stator is fine, and I would tend to think the engine is running too fast causing the higher than normal reading you are getting.
 
  #19  
Old 05-11-05, 09:40 AM
koz
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HI cheese:

I will reset top end speed, replace coil, and fuel solenoid - will see what happens. thanks for all the help

koz
 
  #20  
Old 05-12-05, 01:42 AM
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Good luck! Let us know how it goes.
 
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