Engine runs 20 seconds, then quits

   / Engine runs 20 seconds, then quits #31  
Soundguy said:
I agree. a timed spark plug failure?

almost had to be a cracked insulator that heated up fast and let spark short thru at a very small place/gap.. etc..
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Telling ya,, had the same thing. Run for 10-20 secs then shut down. Cleaned carb twice, then bought coil and plug. Only the plug was needed. Then the other mower did the same thing... Then, my brother called and said Mazda dealer wanted $900+ to replace a coil that was 'missing' according to codes (he had a bad idle miss). Told him to change plugs. Code (miss) is gone.
 
   / Engine runs 20 seconds, then quits #32  
not counting fouled plugs. plugs have to be the most trouble free part of ignitions setups i've ever found.. if you count in wear from electrode erosion.. that bumps capacitors up tot he most reliable.

must be some darn junky plugs being made today...
 
   / Engine runs 20 seconds, then quits #33  
JazzDad said:
This has got me baffled. My JD rider has a PA540A engine in it. It starts very quickly, but then dies after 20 seconds of full throttle running. If I start it then quickly throttle back, it will run for 30 seconds. The fuel tank is not creating a vacuum, because the same symptoms apply if I leave the gas cap off. The fuel shutoff solenoid on the carb is opening, and the float is allowing fuel to flow quite well without the engine running, even through the fuel pump. All the fuel pump baffles/ bellows seem intact and flexing. Nothing seems gummed up in there.

It seems fuel starved to me. Perhaps a fuel line collapsing? I tried dripping gas into the throat of the carb at low speed. It backfired a bit, but still died at the same time (30 seconds)

I have not changed the plug. It just seems too consistent to be the plug heating up and then going bad at the same time, every time.

Replace the fuel lines first (all 5 feet of them)?
Spark plug first?
Remove & thoroughly clean the carb?

Thanks in advance.
Bret
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From iPhone To Tractor-By-Net
 
   / Engine runs 20 seconds, then quits #34  
Spark plugs can really do strange things I guess. Glad you got it running and the grass cut.
 
   / Engine runs 20 seconds, then quits
  • Thread Starter
#35  
Now that I think of it, maybe 22 years on the same plug was a little too much to expect. :confused3:
 
   / Engine runs 20 seconds, then quits #36  
While that may be the fact that it would die after 20 seconds over and over is plain STRANGE. Never hear of that in all my years.

Knew of a guy that worked in a car factory like 50 years ago and his car would die at the same location going to work each day. We are talking low tech car era. Turned out to be a lot of trash in the tank and it would get sucked over the pick up in same amount of miles each day. When it would die the trash would drop back down so it would restart.

Machines can be a mystery. :)
 
   / Engine runs 20 seconds, then quits #37  
20ys on the same plug. i'm surprised it had any electrode left.. :)
 
   / Engine runs 20 seconds, then quits #38  
Depends on use. The one in my Honda push mower I just changed after 15 years..
 
   / Engine runs 20 seconds, then quits #39  
well..i guess if it only gets used 5hrs a year.. then yeah.. :)
 
   / Engine runs 20 seconds, then quits #40  
This is very interesting. In all my years and troubles with small engines, a new spark plug has never ever never been the answer to a starting or running problem.

Glad it all worked out.

MoKelly
 
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