So a little preamble: I'm no certified B&S mechanic or anything, but I'm usually pretty good with small engines. I've rebuilt old Yamaha motorcycle engines, various lawnmower engine, and my 4-cylinder, water-cooled inboard sailboat engine.

But this blankety-blank Briggs & Stratton engine may have me admitting defeat. It's kicking my butt.

I got a Craftsman 6 horsepower 4-in-1 yard vac from cleaning out a lady's shed. It looks to be in pretty darn good condition overall. Except it JUST. WON'T. START.

It seemed like it wasn't getting spark, and the secondary wire was cracked, so I bought a new coil and installed it. Still no love.

The carb was all gummed up, because it seems to have sat for a long time, so I completely disassembled and de-gunkified it. So I'm reasonably sure that carburetion is not the issue.

To try to determine whether it was spark or fuel, I squirted a little butane lighter fuel in the carb just to see if it would "pop". At first I thought it did make a little putt putt, but now I can't get it do anything even with a squirt of butane.

I've tried to see if there is any spark at all by holding the secondary wire up to a head bolt or other component and spinning the flywheel - in the past, when I've done that with other Briggs engines, I usually can easily see a nice blue spark. But I'm getting nothing.

I'm thinking it's potentially something to do with the dang safety switch on the catcher bag. It's pretty clear that switch is a grounding switch, but what I'm trying to figure out is whether it's supposed to be grounded when the bag is connected, allowing the engine to run, or when the bag is NOT connected, which would prevent the engine from running. I'd like to bypass the dang switch to eliminate it as the potential problem, but it seems to me that directly grounding that wire would prevent a spark.

I'm about ready to throw the whole stupid machine off a cliff.

Oh yeah - the B&S engine is a 12H802-1777-D1, in case that helps anyone come up with a blinding flash of brilliant inspiration as to why this @#$#^%@ thing won't start.

 

If you aren't getting spark, remove the kill wire from the coil and see if it sparks then. If not, the coil is bad or installed incorrectly, or upside down.

 

Yes there is a kill switch on the bag, if the bag is out it is dead, if the bag is in it should spark. But like Cheese has said, take off the kill wire under the coil. If it sparks after disconnect there is a problem else where , if no spark replace coil. Check that kill wire very closely as it sometimes will rup through and ground out. Good luck,,,don't give up too quickly,,,,also you might try unplugging that switch for the bag or taping it closed.

 

Make sure ignition coil is properly gapped or has the proper clearance using feeler gauges. Better than just replacing right off? Even if you replace it, you will have to make sure it is spaced properly. I'd try that first. RATO engines, often referred to as the honda of China, have an ignition coil gap of 0.008/in to 0.023/in.

 

I didn't notice in your original post if you replaced the spark plug. I would have assumed you would have tried that before replacing the coil pack.
Normally when trying to start small engines that have sat for some time, I'll remove the plug, put a few small amount of fuel in the cylender, replace the plug and give it a try.
This would prove the engine and ignition is good, and point you to the air/fuel delivery system if it does fire.