Starts, runs for a while, then dies. Then will not start right away.

cjac

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  • / Starts, runs for a while, then dies. Then will not start right away.
Purchase a 10yr old MTD mower with a Briggs & Stratton 4.5hp at a yard sale. Owner was not certain if it would run but I did manage to get it to fire with a few shots of carb cleaner in the carburetor. Decided to clean it up with a good gas tank cleaning, new primer bulb, adjusted governor speed, blade sharpened, carb cleaning (replaced diaphragm), oil change and spark plug renewal, and finally - cleaned/oiled the air filter. Reassembled and filled the gas tank. It started on the 2nd pull and off I go cutting the grass. Ten minutes later the revs dropped off as the engine struggled - then quit. I could not get it going. I performed the following checks:

- check for spark: ok
- check oil level: ok
- check fuel level: full
- checked the kill switch/brake mechanism: not familiar with this but all seemed well

After fiddling around I managed to get it going another 10+ minutes of grass cutting and the same thing happened again. Revs dropped and quit. Acts like it runs out of gas in spite of the tank being full. Did notice the spring ring inside the rubber spark plug boot was broken so it may be a little loose on the spark plug. So I used pliers to squeeze it onto the spark plug. Got it going again but the same issue occurred. I'm at a loss as to what is wrong. Has anyone else experienced such? Very frustrated.
 

cpurvis

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  • / Starts, runs for a while, then dies. Then will not start right away.
Sure does sound like it's fuel starvation.

Let it set for a little while.

Leave the gas cap loose so air can replace the gas drawn from the tank.

Restart and see what happens.
 

cjac

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  • / Starts, runs for a while, then dies. Then will not start right away.
Thanks for the advice. I tried it with a loosened gas cap after sitting. it started again and ran for awhile but conked out again. I switched carb/gas tank assemblies with a similar mower that works and still no luck. Wondering if the coil may be defective?


B & S engine details:
Model Type Code
10T502-0457-B1 07032954



p.s.
Forgot to mention that when I took the cowling off after purchasing there was a rodent nest inside. Think I better investigate again for any wires which may have been chewed on.
 
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cpurvis

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  • / Starts, runs for a while, then dies. Then will not start right away.
In your first post, you said, "--check for spark. OK."

Did you do that check right after it quit running?
 

cjac

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  • / Starts, runs for a while, then dies. Then will not start right away.
No, I did not think to as I was focusing on a fuel issue. Next time it conks out I will check for spark immediately.
 

primerbulb120

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  • / Starts, runs for a while, then dies. Then will not start right away.
I'm thinking either ignition coil or a sticking valve.
 

zack50

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  • / Starts, runs for a while, then dies. Then will not start right away.
Sure does sound like it's fuel starvation.

Let it set for a little while.

Leave the gas cap loose so air can replace the gas drawn from the tank.

Restart and see what happens.

i did that restarted and stoped again
 

bertsmobile1

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  • / Starts, runs for a while, then dies. Then will not start right away.
When it stops give it a squirt of starter fluid or carb cleaner down the carb.
If it fires up & runs till it burns off the spray then you have a fuel supply problem.
Get an inline spark tester install that and go mow
When it stops have a quick look at the tester when cranking
No spark = ignition problem
spark = fuel / valve problem.
 

DAMatson

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  • / Starts, runs for a while, then dies. Then will not start right away.
I am definitely in the fuel supply category.

As recently as of last summer (August of 2018) I had already completed the following:

  • replaced the starter solenoid (and added rock-solid ground wire),
  • replaced the entire carburetor (this one had a backfire inhibitor solenoid built-in; luckily my existing electrical harness had a positive wire sitting nearby unused, just had to create a ground wire),
  • and lastly replaced the battery.

So Saturday I pulled the tractor out of the shed, cleaned it off of debris, filled the tank with gas and "Mechanic in a bottle" additive, topped-off the oil, cleaned all the primary electrical connections with a wire brush, and checked the air filter (already clean). Before replacing the air filter, I poured a few drops of gas into the throat of the carb to prime the starting process.

Then I started the mower: It took a few seconds of cranking but it started and ran clean. Continued to run clean while I cleared the yard of obstancles (pulled a hose out of the way).

After it was warmed-up, I was able to clear about six lengths of the yard, going very slowly because the grass was taller than I would have liked. After an hour I had cleared a swath equal to about a quarter of the total yard, so I disengaged the blades and drove up to the house to get some water. Sadly, about halfway there the engine started to sputter and then died.

I can start it relatively easily (starts after 10 seconds of cranking), and then it sounds perfectly ok to me, and continues to run for about 30 seconds to a minute, but somewhere in there it will just sputter and die. If I pour a bit of gas into the throat of the plastic assembly in front of the carb when it starts to die, it'll continue to run further, then die when it burns through the remaining fuel. It dies whether or not the blades are engaged, and whether or not the gears are active.

Any other suggestions before I pull the carburetor off and tear it apart to inspect it further?

-David
 

bertsmobile1

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  • / Starts, runs for a while, then dies. Then will not start right away.
Dave,
Do not know why you tacked this post onto an old thread but the fuel test proves you have a fuel supply problem.
Can be anywhere from the tank cap through to the carb.
Start by loosening the tank cap the instant the engine stops.
If you hear it suck as the cap is unscrewed the the cap is bad.
If the cap is the only problem then it should run fine if the cap is loose.
 
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