# Advice for novice? Toro engine dies when warm.



## Engineeringtech (Aug 9, 2008)

Hi!

I don't have any experience troubleshooting small engines, and was hoping to get some basic guidance for a mower that dies after it warms up. This is a Toro 16575 with a Tecumseh TVS-100 engine. 20 years old, but I like it and hate to get rid of it. I always put Stabil in the tank when I store it for the winter. I keep the oil changed, air filter clean, blade sharp, and deck reasonably clean. New spark plug every couple years. The engine had a bit of caked on mud and dirt in places (but I just cleaned that off).

I've been using it this summer with no problems. Ran out of gas while mowing a couple days ago, and bought some new. Put it in, and ran a few more rows before the mower sputtered and died. There's a clear fuel line filter between the gas tank and carb. It looks clean, and I can see gas in it. But I didn't know if it was flowing, and didn't want to pull the line off to see for fear of a fire. I looked at the plug. A little dark, but showing no erosion of the electrode. Let the mower cool down, and it restarted no problem. Mowed a few more rows, and it died again. Let it cool, and again I had the same symptom.

Do you think this is a fuel problem or a ignition problem? Any ideas on the fastest way to troubleshoot this?


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## geogrubb (Jul 28, 2006)

Sometimes the fuel cap will come apart and the cone part will block the fuel outlet, check the fuel cap. Refer to the picture below as an example. Have a good one. Geo


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## 30yearTech (Sep 14, 2006)

Could also be that the fuel cap is not venting properly and you are getting a vacuum in the tank after it runs a short while, try loosening the cap and see if it will run after this, if so, look for a blocked vent.

If it's the style cap pictured in geo's post, then if the gasket behind the splash plate comes off with the metal disc, this will block the venting of this style cap, causing a similar problem.


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## pyro_maniac69 (Aug 12, 2007)

or if the cap is in the gas tank, it might be getting sucked over the screen in the tank


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## 30yearTech (Sep 14, 2006)

pyro_maniac69 said:


> or if the cap is in the gas tank, it might be getting sucked over the screen in the tank


How does one get the cap in the fuel tank??


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## hans747 (Jun 29, 2009)

I think he means that little metal disc thing falling into the gas tank.


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## 30yearTech (Sep 14, 2006)

hans747 said:


> I think he means that little metal disc thing falling into the gas tank.


I know, it's the devil in me.... Got to give pyro a hard time


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## Rentahusband (Aug 25, 2008)

20yrs old and your description, sounds to me like the coil is bad. Have you checked for spark when it does not start? 
Dean


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## Engineeringtech (Aug 9, 2008)

*My apologies...*

My apologies and thank you to all who replied. I have been having problems with my computer, and I somehow lost my bookmark to the forum. The mower problem went away for a couple weeks, but now it has returned. 

I was convinced, since the problem started same day as I got a new can of gas, that the problem was water or dirty gas. But the fuel filter is flowing just fine. And when I poured the gas into a clear glass bottle, I did not see any water.

The cap on this motor is not like that shown in the pictures. It has no metal disk. There is a plastic dome under the cap. So I don't think that's the problem. 

I have noticed that the spark plug "soots up" very quickly. It is not oily, just sooty. The air filter is clean, and I haven't adjusted the carburetor. So that sure does sound like an ignition problem. So it might be the coil.

I'm going to order a new coil, replace the fuel filter and hoses, and clean the carburetor, just to be safe.

Thanks for the help everyone.

JC


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## geogrubb (Jul 28, 2006)

Before you order a new coil, clamp off the fuel line and remove it from the carb or use another piece of hose and attach it to the fuel tank then with the fuel cap in place and the mower on a level surface let the fuel run from the tank into a bottle/pan/whatever to see if the flow slows to a trickle or maintains a steady flow and drains the tank. I it slows to a trickle it's a bad cap. Have a good one. Geo


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## pyro_maniac69 (Aug 12, 2007)

30yearTech said:


> I know, it's the devil in me.... Got to give pyro a hard time


ya, and you LOVE doing it to a hole lol


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## Engineeringtech (Aug 9, 2008)

I pulled the hose off the carb, put the end in a bottle, and confirmed that I had good flow from the fuel tank, through the filter. 

I had the notion the spark was weak because the plug "sooted up" so quickly. I got some of that self fusing silicone rubber tape electricians sometimes use, and wrapped it around the sparkplug lead all the way to the coil, insulating it from the sheet metal covering the top of the motor. That seemed to help a lot. Maybe the insulation on this 20 year old mower's ignition wire was broken down? 

I also installed a hotter spark plug. I have not had any problems since.


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## 440s-4ever (Feb 23, 2010)

Insulation on the plug wire should not affect spark strength unless moisture gets into the break or the wire's allowing a direct short. It's pretty much an all or nothing thing, either your spark goes across the plug, or it jumps elsewhere. Not like a leaky water pipe where something still gets delivered, but at a reduced strength.

However, 20 years is a lot for a plug wire, and they'll gain resistance or suffer internal breaks which does affect spark strength. Coils are also known to work when cool then fail when hot, but usually the symptom gets progressively worse without improvement you report. 

Did you inspect the old plug closely? Sometimes a cracked insulator will do goofy things.

I'm tempted to believe the tape job stabilized the bad spot in your plug wire core. 

If it happens again pull the plug, use a wire with alligator clips to ground the plug body or have a helper touch the plug to the engine. Pull the cord and look for spark. 

Here's a troubleshooting tip........are you suuuure the "out of gas" was actually out of gas and not the first instance of shutdown? Defining that as a potential cause or a potential symptom points you in different directions. Plus it could be total coincidence. 

In the future if you remove the carb's drain plug or float bowl (1 bolt) then you can verify flow past the needle & seat which is a problem spot for small engine fuel delivery. In the process you often flush a bit of debris. 

Good luck!


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