16.5 Briggs Flooding (Strange Issue)

Reply

  #1  
Old 08-31-08, 09:25 AM
Member
Thread Starter
Join Date: Aug 2008
Location: Athens, AL
Posts: 4
16.5 Briggs Flooding (Strange Issue)

This one is baffling me. I have a 16.5 Briggs I/C on an MTD riding mower. It started running rough and I tracked it down to a VERY dirty air filter (shame on me). I took the filter off and it ran okay to finish the small area I needed to do. I ordered a filter and let the mower sit until it came in. Put the filter on and it wouldn't start. I take the filter off and it runs for a bit, but then stalls. Okay, filter back off so I can see what's happening. What I see just amazes me. The engine will run (after some coaxing, explained in a minute) for a bit until it clears itself out, then it will suddenly "cough up" a bunch of liquid (what was later determined to be gas) from the top of the carb down into and around the choke to the point where it literally stalls and stops the engine solid. This forces the engine to stop. The engine will start again after the fuel evaporates, and the cycles repeats. Nothing has changed. I'm at a loss. Any help/thoughts you can provide is appreciated. (I don't work on small engines, so if you can "dummy" this down it would be great.) I'll be thinking about this as I go get my new mower, and the "For Sale" sign for this one. Thanks in advance!
 
Sponsored Links
  #2  
Old 08-31-08, 10:01 AM
Member
Join Date: Jun 2008
Location: GA
Posts: 150
It sounds like there's something affecting the operation of the float in the carburetor, causing the fuel inlet valve to stick open. When the bowl gets full, the gas is forced into the throat, causing the engine to flood and stop.

You'll need to disassemble the carb to see what's going on with the float and valve. A little cleaning will probably fix it right up. Worst case is probably a leaky float, which will have to be replaced.
 
  #3  
Old 08-31-08, 10:03 AM
Member
Join Date: Feb 2006
Location: Indiana
Posts: 423
Remove ALL the fuel, blow off the spark plug after you have dipped it in some fresh gas. Then refill the tank with CLEAN FRESH FUEL, and see what happens. It may require a few chances to stay running as bad fuel may still be in carb.

Before you do any of what I have suggested above, do this. REMOVE THE GAS FILLER CAP SLOWLY, SO AS NOT TO SLOSH THE FUEL IN THE TANK, TAKE A FLASH LIGHT, NOT A MATCH, AND SHINE DOWN INTO THE TANK, AND SEE IF ANY BUBBLES OR POOLS OF WATER ARE IN THE BOTTOM OF THE TANK. I am suggesting WATER in the tank, and or dirty tank.

Worth a try.......


Dale in Indy
 
  #4  
Old 08-31-08, 11:02 AM
Member
Join Date: Jun 2008
Location: GA
Posts: 150
I believe Dale's reply should have gone on the thread about
dave237's Carb/intake Problem.
 
  #5  
Old 08-31-08, 12:51 PM
Member
Thread Starter
Join Date: Aug 2008
Location: Athens, AL
Posts: 4
Originally Posted by rogerflies View Post
It sounds like there's something affecting the operation of the float in the carburetor, causing the fuel inlet valve to stick open. When the bowl gets full, the gas is forced into the throat, causing the engine to flood and stop.

You'll need to disassemble the carb to see what's going on with the float and valve. A little cleaning will probably fix it right up. Worst case is probably a leaky float, which will have to be replaced.
Thanks for the quick response Roger. Not to sound ignorant - would this cause the fuel to dump, and I mean *literally* into the top of the carb? It rush in like Niagara Falls to the point where it stalls the engine out. I can't turn the engine over because the compression chamber is full of fuel. If I cycle the engine a few times it will eventually push the fuel through the exhaust, and then it will start, burn the fuel off, run for about 30~60 seconds and puke into the carb again. Strangest thing I have ever seen. (Then again I haven't seen fuel dump in from that part of the carb either, but it's OBVIOUSLY some sort of chute/slide for something ..)
 
  #6  
Old 08-31-08, 02:27 PM
Member
Join Date: Jun 2008
Location: GA
Posts: 150
I could tell for sure if you posted a picture of the carb, but my guess is that it's a vent for the bowl.

30-60 seconds is about how long it would take to empty the carburetor bowl if there's no fuel coming in through the inlet valve.

Normally, the float drops down a little, that lets in some gas, the float moves, and the valve closes. This happens over and over very quickly with little variation in the level of gas in the bowl. Something in the float/valve mechanism is causing the valve to stay closed until the bowl empties, then open until it overflows.

I think it'll be an easy fix if you take the top off the carb to see what's going on. It's a simple mechanism. The valve parts look like this:

the float looks like this:
 
  #7  
Old 08-31-08, 04:25 PM
Member
Join Date: Jun 2008
Location: GA
Posts: 150
I'm going to make a guess as to what you're going to find when you take the top off the carb.

I think the little wire clip has come off the groove on the valve plunger. That'll let the float move down without pulling the valve open to let more gas in. Then the valve plunger will drop down. More gas comes in, but the plunger binds as it goes up, causing the bowl to overflow. When the plunger finally does go up, it sticks in the seat because it goes up so suddenly instead of slowly. And the cycle repeats.

Putting the clip around the groove in the plunger will fix it.

It's either that or trash in the bowl.
 
  #8  
Old 08-31-08, 06:35 PM
Member
Thread Starter
Join Date: Aug 2008
Location: Athens, AL
Posts: 4
Originally Posted by rogerflies View Post
I could tell for sure if you posted a picture of the carb, but my guess is that it's a vent for the bowl.
Sorry - all I have to post too is a cheap Flickr account, so here goes. Fingers crossed you'll get them! If not, I'll think of something else.

Niagara Falls flows from here:

http://www.flickr.com/gp/[email protected]/uG62Z6

Here's a side view of the dirty thing:

http://www.flickr.com/gp/[email protected]/fpfx86

This shows the linkage:

http://www.flickr.com/gp/[email protected]/7f1Fcp

I'm sure that a "Nikki" brand means it's either super gee whiz or super junk (I'm guessing the latter):

http://www.flickr.com/gp/[email protected]/829ith

More linkage - all looking a-okay!

http://www.flickr.com/gp/[email protected]/65r8hi
 
  #9  
Old 08-31-08, 07:45 PM
30yearTech's Avatar
Member
Join Date: Oct 2006
Location: Central Texas
Posts: 1,176
Check the oil level in your engine. It may be contaminated with fuel and is overfull. This will allow the engine to run a short time and the breather will fill with fuel and oil and feed directly into the top of the carburetor via the breather tube.

The Nikki carburetor should have a plastic float and will not have the spring clip as pictured in the other post.

If the oil level is correct, then the problem may lie in the carburetor, but I would find it unusual that your carburetor would only flood when the engine is running. If you do have your oil contaminated with fuel, then the problem lies in the carburetor and will have to be corrected, you will also need to drain all your oil and refill to proper level with clean motor oil.

Best of Luck... Let us know what you find...
 
  #10  
Old 09-01-08, 04:07 PM
Member
Thread Starter
Join Date: Aug 2008
Location: Athens, AL
Posts: 4
Thumbs up

All,

I checked the oil level in the engine and it looked okay, but it was definately thinned out from the gas (to the point where it was really more gas than oil). I drained it completely, as well as the filter, and refilled it with fresh oil to capacity (48oz). After frying both a battery and a $300 commercial battery charger, I bought a new battery and held my breath as I cranked it over. It sputtered and coughed, but cranked and eventually started. I let it run (with air filter on) and it cleared itself out and acted "normal". I was able to mow all my yard (a half acre) without any problems! (It's still going up for sale though Anyone interested? Lots of new parts. Looks good, runs great now. Heh heh. I'll deliver within reason ..)

Many thanks to everyone! I am very impressed with the help I got here. Kudos!!
 
  #11  
Old 09-02-08, 12:13 AM
cheese's Avatar
Forum Topic Moderator
Join Date: Jul 2001
Location: USA
Posts: 16,814
Glad you got it going, but if you didn't fix the carb problem, it will do the same thing all over again.
 
  #12  
Old 09-03-08, 04:21 PM
Member
Join Date: Aug 2008
Location: San Francisco Bay Area
Posts: 12
flooding

Absolutely right - no fix? Will still flood and dump fuel when sitting. Could cost you an engine, maybe catch on fire.

Once fixed, consider installing a manual shut-off valve at the caruretor inlet. Especiall if the tractor sits for extended periods.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes