Briggs & Stratton no start: magneto?


Old 07-25-04, 01:45 PM
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Join Date: Mar 2002
Location: USA
Posts: 146
Angry Briggs & Stratton no start: magneto?

I filled the tank on my Cub Cadet mower and managed to mow about 50 yards when the engine died on me.

I was unable to get it to restart.

My first thought is contaminated fuel. I drained the tank and there was water in the fuel. So I drained the tank, got fresh gas, filled it up, still won't start.

Air filter is clean.

I don't know much about carbeurators, but I removed it and verified that the float valve is working, both by blowing into the inlet tube and allowing fuel to flow through it. Valve down, fuel flows. Float up, no fuel. (I would have to refer to any other part of the carb as a "doohickey.")

I was unable to get a spark using the screwdriver-close-to-the-frame method. I was in a dimly lit garage so I think I should be able to see the spark if it was there. I'm confused though; I wouldn't expect the spark to die in the middle of mowing like that. Especially just after filling the tank from a jug that had been unsealed and later proved to have water in it. But who knows.

I've verified that the deadman switch does open and close properly when the "hold this bar to run the mower" bar is held. (The other end of the wire is grounded when the bar is released, open circuit when bar is held.)

Is there any easy way to test the magneto? I'd hate to go out and buy one if it's not needed.

Edit: The engine is a 6.75 HP pull-start on a 3 year old cub cadet self-propelled push mower.
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Old 07-25-04, 02:01 PM
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Join Date: Apr 2004
Location: Upstate New York
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You stated you tested for spark by using a screwdriver. The best way (without proper tools) is to use a known good spark plug, insert it into the plug wire, lay the plug on the head (or anything metalic), pull the engine over and check for spark. If you find no spark the next step is to remove the kill wire from the ignition coil and again check for spark. If no spark, replace the coil. If spark and since your mower likely doesn't have any safety switches, the flywheel brake cable may not be pulling the brake/engine-kill-mechanism far enough, OR the brake/engine-kill-mechanism itself may be at fault. The coil certainly can and will break down at any given time.
Old 07-26-04, 08:21 AM
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Join Date: Mar 2002
Location: USA
Posts: 146
Thanks for the feedback.

I did inspect the brake/kill switch and tested continuity of the switch both with the bar released and held in operating position. The kill switch appears to be working fine.

Looks like I'll go out and buy a new ignition coil.
Old 08-04-04, 10:19 AM
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Join Date: Mar 2002
Location: USA
Posts: 146
Good news!

A new ignition coil and a few dozen good yanks on the starter cord fixed the problem.

New problem is that the speed governor is oscillating, but I'll post that as a new thread.

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