First time for everything....Gasoline fireball in a tractor

baymee(LehighValleyPA)May 5, 2012

Today was a first and a good lesson learned.

I was working on a tractor that wouldn't crank through one revolution because the valves were too loose. After adjusting the valves yesterday, it was starting like normal.

I went out this morning to double check the starting before returning it to the customer. It turned until compression and stopped. A few tries later, it still wouldn't crank through compression. So, I'm thinking wth, this worked great last night.

I removed the plug and saw that it was wet, so I moved the tractor outside, like I do all equipment with suspected gas in the cylinder. I cranked the engine and the gas blew out against the front of the hood and erupted into a 2 foot round fireball. I guess the plug wire was close enough to metal that a spark formed.

Well, no damage done, except that I've done this a hundred times before with pushmowers and never had ignition.

Keep this in mind next time this happens to you.

I drained the entire fuel system and thoroughly cleaned the fuel line and needle/seat. I have the plug out now and will see if any gas is leaking past the seat tomorrow.

If there is gas in the cylinder again, I'll crank it over to get it o.......maybe I won't do that any time soon lol.

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I remember making grounding clips for plug wires way back in the 60's.. still got them and still use them.

I also remember a learning experience like baymee's and I bought a fire extinguisher... still got it and never used it. I have it checked every year. It was a great investment

    Bookmark   May 5, 2012 at 7:54PM
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Grounding clips (just cheap Radio Shack test leads with an alligator clip on each end) are a very good idea for TWO reasons.

1. prevents fires as in your case.
2. When the high tension wire is out in "mid air", the coil can build up excessive voltage trying to fire the spark plug and actually break down the internal insulation by shorting to itself internally.
Not so much a problem on L&G engines, but definitely on automotive type systems.

    Bookmark   May 5, 2012 at 8:21PM
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Heh heh! Glad only your pride and wits got hurt.
A simple but effective method I used to prevent errant sparks from ruining the whole day is to soak a plain paper towel or wash cloth with tap water and then wrap the end of the spark plug cable and boot in this wet towel.
The water will provide for a "sparkless" transfer of energy to dissipate harmlessly into the metal surface you lay it on.
It's not better than grounding clips, but it is available to anybody.......even if they are "tool challenged".

    Bookmark   May 6, 2012 at 8:04PM
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