I added Sta-Bil and the engine started knocking. Uh Oh...

[MIHELA]

Sounds like a light rod knock to me. That double knock at twice the crank speed is from the rod knocking on the up and down strokes. Valvetrain noise would be at half engine speed, and crank knock like my truck did sounds more like a diesel and at crank speed.

 

[454cid]

First Guess: Total coincidence that the truck started knocking. I've lost all faith in Sta-Bil doing ANYTHING--useful or harmful. I used it for years on seasonal engines. Then I quit using it, and never noticed any difference.

I'm thinking this too. I can't see a few onces of something, diluted in a full tank of gas, causing a knock.... unless it was something like Nitromethane, maybe?

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[GoToGuy]

What properties does a fuel stabilizing product have that could cause catastrophic engine damage? If thats a possibility would not have some shadetree backyard rocket scientist allready proved that theory? Uber explosive properties, not in a consumer product. The last time i personally had a knocking noise, i looked under at oil pan, and looked like a 30.06 had excited the left side of the sump. And open the patient up. Bingo broken crank journal, a connecting rod broken in half midbeam. The same piston in 11 pieces. Pin laying in bottom of pan. The broken con rod had 3 inches of # 5 rod flinging around in crankcase lower block chewed a half moon groove in block. The crank broke completely so two piece crankshaft. The break went at angle top left through the 5 and 6 journal to lower right. So the 5 and 6 con rods were holding the two piece crank together. A massive piece of scrap. I kept the one broke in half con rod. A memory of a four speed didn't shift completely and the tach blurring past 6500. I agree that pulling plug wire off shutting down a cylinder one at time. Without the cumbustion cycle the load on the those affected parts changes and could narrow down a suspect cylinder. Good luck.

 

[Schurkey]

1. I used to run a Nitromethane/Alcohol engine, years ago. Decades ago, really. I was about twelve. Don't be too impressed.

Single cylinder, C_ox Babe Bee ".049" model-aircraft job. C_ox Glow Fuel had nitro in it. Not many folks realized that. I can only imagine today's libtaard reaction to kids playing with Nitro. Which is probably why they went out of business in '06. At this point, I have to screw-up the spelling of the brand-name "C_ox" to get it past the censors.

Cox model engine - Wikipedia

en.wikipedia.org

2. Don't pull the plug wire OFF--which causes an open circuit on the ignition secondary, driving the voltage sky-high leading to potential problems with the cap, rotor, ignition coil, and plug wire insulation. GROUND the spark sequentially to each cylinder. Blunt the sharp tips of eight small nails. Grease them with some silicone dielectric grease. SLIDE the nails BETWEEN the plug wire and the boot at the distributor cap end (Don't puncture the wire or the boot) until you feel it touch the metal plug wire end. Start the engine, use a grounded test light or jumper wire touching each nail in sequence to eliminate spark to each cylinder in turn.

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Remove the nails when you're done--they'll ground on the air cleaner.

3. I had a Honda Civic blow a hole through the front of the block at 58K miles, 70 mph, 5th gear. All the main bearings, and the other three rod bearings looked beautiful. #3 rod bearing was burnt black, sharp enough to shave with. That rod was the only broken connecting rod I've ever seen in real life where the rod broke--but the rod bolts didn't. Bent 'em some, but they didn't break. The rod was in four pieces. I saved the rod for years, I think it got lost when my garage burned down. I have a digital photo that I took of a damaged Polaroid photo.

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[TechNova]

2. Don't pull the plug wire OFF--which causes an open circuit on the ignition secondary, driving the voltage sky-high leading to potential problems with the cap, rotor, ignition coil, and plug wire insulation. GROUND the spark sequentially to each cylinder. Blunt the sharp tips of eight small nails. Grease them with some silicone dielectric grease. SLIDE the nails BETWEEN the plug wire and the boot at the distributor cap end (Don't puncture the wire or the boot) until you feel it touch the metal plug wire end. Start the engine, use a grounded test light or jumper wire touching each nail in sequence to eliminate spark to each cylinder in turn.


just slide those nails in by hand with the engine running, you'll know when they make contact

 

[JimFixes]

1. I used to run a Nitromethane/Alcohol engine, years ago. Decades ago, really. I was about twelve. Don't be too impressed.

Single cylinder, C_ox Babe Bee ".049" model-aircraft job. C_ox Glow Fuel had nitro in it. Not many folks realized that. I can only imagine today's libtaard reaction to kids playing with Nitro. Which is probably why they went out of business in '06. At this point, I have to screw-up the spelling of the brand-name "C_ox" to get it past the censors.

Cox model engine - Wikipedia

en.wikipedia.org

2. Don't pull the plug wire OFF--which causes an open circuit on the ignition secondary, driving the voltage sky-high leading to potential problems with the cap, rotor, ignition coil, and plug wire insulation. GROUND the spark sequentially to each cylinder. Blunt the sharp tips of eight small nails. Grease them with some silicone dielectric grease. SLIDE the nails BETWEEN the plug wire and the boot at the distributor cap end (Don't puncture the wire or the boot) until you feel it touch the metal plug wire end. Start the engine, use a grounded test light or jumper wire touching each nail in sequence to eliminate spark to each cylinder in turn.

You must be registered for see images attach

Remove the nails when you're done--they'll ground on the air cleaner.

Now that's a damned Shadetree trick if I ever saw one. Love it!

I had a bunch of cleaning to do on the garage today, but I will be out there futzing with her tomorrow and figure out the issue.

 

[Chuck_13]

FWIW I've had very good luck with Stabil,good enough that I use it to treat every can of gas (for use during hurricanes etc) with it.Years ago I had a first gen Honda Goldwing,they were/are notorious for carb problems do to the crappy gas we had,and still have.Using Stabil I could leave the bike parked the 28 i was at work and it would fire up with no drama when I GOT HOME.Made me a believer in Stabil.And no,i don't own any Stabil stock,

 

[thegawd]

I have only really used stablil in my boats gas, if I have a bunch left in the can for winter storage. this dosent happen often though. Instead I only buy top tier gas thats ethanol free. I have never found this gas to ever go bad. I drain or run the fuel out of most of my small engines and sometimes I just empty the carburetor. they all start as soon as fuel hits the spark.

man I spent many years buying the cheapest gas and then cleaning and rebuilding carburetors every spring.

now I buy some of the most expensive gas and save my labour for something else. I call it preventative maintenance.

 

[reservoir dog]

Could it be a piece of carbon broke loose from the top of a piston, I have heard that sound like a knock. I'm at work and could not listen to the video.

 

[454cid]

I have only really used stablil in my boats gas, if I have a bunch left in the can for winter storage. this dosent happen often though. Instead I only buy top tier gas thats ethanol free. I have never found this gas to ever go bad. I drain or run the fuel out of most of my small engines and sometimes I just empty the carburetor. they all start as soon as fuel hits the spark.

man I spent many years buying the cheapest gas and then cleaning and rebuilding carburetors every spring.

now I buy some of the most expensive gas and save my labour for something else. I call it preventative maintenance.

I've never really had issues with previous season gas, and I don't add anything..... speaking mainly of mowers, and roto-tiller. First startup of the season I have to crank it over more times than normal, but after that, they're fine. I do normally by Premium for small engines, but it probably still has ethanol in it. They don't have to label the ethanol content in MI. I have recently learned that we do have a couple of places to buy non-ethanol fuel, in town, but I have yet to actually buy it.

I do run the snow blower out of gas at the end of the season, and that's the engine that won't start, right now. :-/