Briggs and stratton Engine popping while running?

[chad22]

On my garden tractor that's in my avatar I have an 18hp Briggs and Stratton Opposed twin engine It's a pretty old engine probably in the 90's.

Anyway it was running good for awhile until it sat waiting for the new starter to arrive. I put the new starter on today and it fired right up.

The engine runs fine even under load. But it pops while running.

Could moisture in the fuel cause this popping?

I changed the spark plugs with 2 new ones and it still didn't cure the problem.

Thanks

Chad

 

[deerseeker001]

Did you check the gap on the plugs

 

[smstonypoint]

By popping, do you mean as in a backfire?

Steve

 

[chad22]

By popping, do you mean as in a backfire?

Steve

Yeah I believe it's backfiring. It goes pop, pop, pop, pop, pop. I did check and set the gap when I installed the plugs.

It did sit out in some snow and the tarp I had over the engine blew off and there was a pile of snow on the engine,breather cover and fuel tank.

So that's why I'm thinking it might be some water in the fuel as it wasn't popping like that before the engine and fuel tank got covered in snow.

That's why I was wondering if water in fuel could cause the popping of the engine.

I'll run the current fuel out tomorrow which isn't much, drain the tank, clean it and put fresh fuel and see if the condition exists.

Thanks for the help guys I really appreciate it.

Chad

 

[jaotguy]

if its consistently popping , its not the gas .... bad plug, valves or no spark to 1 cylinder.

most likely a sticking valve on one of the cylinders if it "just happened" all of a sudden . Happens a lot on older B&S engines.

 

[sampen]

Water will also cause this problem drain carb to verify. If carb has water in it drain tank I wouldn't take head off til you verify it. You could do a leak down test to verify stuck valve assuming you have a leak down tester.
Sam
Also if you need any parts for this engine I have alot of new parts for the opposing twin!

 

[Gator6x4]

If you can do so safely, remove the air breather cover and watch the throat of the carburetor with the engine running. Look for spitting when the engine pops. If spitting do a compression check and see if a intake or exhaust valve is sticking. You may also put a strong Marvel Mystery Oil mixture in the gas and also add marvel mystery oil to the oil in the crankcase and run the engine. Varnish may be causing a problem.

 

[chad22]

Thanks for the help and suggestions everyone.

I was gonna work on it yesterday but it was too cold outside to work with it. It only got to 20F yesterday so I decided to wait until later this week when it gets into the 50'sF.

It's only 20F again today and we're getting a little bit more snow.

I'll report back when I check the carb this week. I think I'll drain the tank completely and the carb as well.

I'm hoping it's just water in the fuel and it clears up with the draining of the carb and tank.

I'll also have to hunt down my spark tester that should be in our shop somewhere. Then I'll also check for spark on each cylinder while it's running.

Chad

 

[smstonypoint]

Chad,

If it's not the fuel, it could be a faulty coil.

Steve

 

[arlen4720]

A friend of mine had this happen to his briggs after storage, and it tured out to be the carb jet was fouled just a little bit with varnish. He just did a quick carb teardown and clean, and everything is good again.

 

[3930dave]

A dose of Seafoam in the gas won't hurt, and may help with a varnish or minor water issue.

Rgds, D.

 

[Deekes]

After you have exausted the good suggestions of all these members, try this. Critters, mice to be exact love to build their nests in the cooling fins of the engine. Take the shroud completely off and inspect for any tenants that may have taken claim. The engine will overheat enough to cause this symptom. Be vigilant, the little buggers can really pack it in there. I've experienced this more than once and a heavy blast of compressed air sometimes could not free it. They are determined little builders. Good luck.

 

[3930dave]

After you have exausted the good suggestions of all these members, try this. Critters, mice to be exact love to build their nests in the cooling fins of the engine. Take the shroud completely off and inspect for any tenants that may have taken claim. The engine will overheat enough to cause this symptom. Be vigilant, the little buggers can really pack it in there. I've experienced this more than once and a heavy blast of compressed air sometimes could not free it. They are determined little builders. Good luck.

Good point. Buddy of mine pulled about 10lbs of "mouse hotel" out of an RV generator one day.

Rgds, D.

 

[Mattc8832]

A new plug with the gap set about .030 would probably fix the issue.

 

[The Fred]

if its consistently popping , its not the gas .... bad plug, valves or no spark to 1 cylinder.

most likely a sticking valve on one of the cylinders if it "just happened" all of a sudden . Happens a lot on older B&S engines.

Baseline the engine first. Chances are a valve not seating or compression release sticking?? Broken valve spring?? Compression and leakdown test is in order before wasting UN-needed time.

Regards, Fred

 

[downsizingnow48]

I grew up in suburban southern California. Everyone had lawnmowers and they all had Briggs engines and they all popped. I used to routinely take the engine apart, clean the valve stems and guides, and lap the valves, which worked for a season or so before the popping started again.

 

[chad22]

I forgot to update this thread.

It finally stopped popping after draining the fuel tank and cleaning it out. There was indeed water in the fuel.

Now it runs great without the popping.

Thanks for the help guys.

Chad

 

[Baby Grand]

I forgot to update this thread.

It finally stopped popping after draining the fuel tank and cleaning it out. There was indeed water in the fuel.

Now it runs great without the popping.

Thanks for the help guys.

Chad

Thanks for posting the cause, Chad. YOu just made this a much more useful thread for anyone having the same problem.
You'd be surprised how many threads end without any explanation of what was actually causing the problem.

 

[3930dave]

Thanks for the update Chad.

Esp. if you have to use Ethanol contaminated fuel, using something like Stabil, Startron, etc.... is a good idea with seasonal or low use equipment.

Rgds, D.