Briggs engine surges then dies

mean_green06June 15, 2006

I have a 3 year old lawn machines mower...self-prop,6.25hp Briggs & Stratton quantum engine, series 120000. I bought it brand new and it ran fine for the first season then midway last season it would start and run fine anwhere from 2-5 minutes then out of the blue the engine will surge for about 5-10 seconds then just die. It will restart after cooling off a few minutes but I haven't been able to locate the problem and its driving me nuts! I have drained the gas after each season and replace the oil, plug and air filter at the start of each new season...using fresh gaasoline also. This problem has only gotten even worse and now the mower doesnt run very long at all before it begins to surge and die. Two days ago i removed the carb, took off the float bowl and cleaned passages as best i could and it is still surging. I even installed an in-line fuel filter and the problem hasnt changed. I have worked on cars for over 10 years so i feel confident about my work but maybe i'm missing something that you guys can help me out with?? The only thing left to be replaced is the muffler but would that cause this condition? The muffler did not appear clogged when i removed it so i have no clue what to do next. Please help..

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How did you clean the carburetor passages? The use of fuel or perhaps Kerosene is not effective in cleaning carburetor passages. Spray carburetor cleaner (from an auto store) is the most powerful solvent for cleaning carburetors. On the Quantum engine, the bowl nut contains the main metering jet and while it may look clean, sometimes fuel varnish blocks some fuel flow.

Another possible cause of the problem may be water in the fuel or perhaps in your spare fuel can. Check the cross-over intake tube for signs of an air leak. There should be an o ring on the tube where the carburetor mounts.

    Bookmark   June 15, 2006 at 1:14AM
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Yes I used carb cleaneer to clean out the passages then blew them out using compressed air. Ive NEVER used fuel to clean any parts so that wouldnt be an issue here. Im not exactly a "master mechanic" but using fuel to clean any part especially a carb just doesnt seem like common sense to me. Anyway perhaps soaking the metering jet in parts cleaner would help dislodge whatever may be blocking the openings..if thats the case? And yes i did notice the o-ring where the carb mounts and replaced it. I also forgot to mention in the original post that i replaced the fuel cap after i reinstalled carb. Ive been told by a few others that this is sometimes the cause of the symptoms ive been having...but unfortanetly it had no effect. I think i will try cleaning the muffler next but i would thnk if it were plugged the engine would run very rough, which it isnt but at this point I will sure give it a try. Any other suggetions are welcome...

    Bookmark   June 15, 2006 at 3:32AM
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Sounds like water in your gas to me.

    Bookmark   June 16, 2006 at 10:50AM
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try immediately loosening the gas cap the next time.

    Bookmark   June 16, 2006 at 11:19AM
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Well im almost certain theres no water in the fuel as I've tried 3 fresh batches of fuel on an empty cleaned out fuel tank, and everytime it still does the same thing. How do you guys feel about those fuel stabilizers/additives(stabil)?? Baymee, what should i be expecting to happen if i did that? I tried it on the last mow and fuel was squirting from the tank and it still surged and died so i'm not sure what i am lookin for there. Any idea how much a new carb for that engine would be? At this point i'd thnk id rather replace it instead of going thru the same crap week after week or having to wait for a repair shop to look at it.

    Bookmark   June 20, 2006 at 1:51AM
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jwor620(z8 Tx)

When this mower dies have you checked for the usual things like spark? Does this mower have a primer bulb? If so, can you push the primer bulb and the mower recover for a moment or so? No spark could be a heat related issue with the Coil. The gas cap issue I have experienced on an older Briggs 5 horse. If the vent for the cap is plugged, it will keep fuel from flowing properly and it could take up to 10 minutes of running for the issue to edify itself.

    Bookmark   June 20, 2006 at 5:28AM
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Post the engine's exact model numbers, so we know what you
series 120000 tells us little but the displacement, if it
is an ohv, my reply would be a simple one.


    Bookmark   June 20, 2006 at 7:09AM
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Hello out there. I'm posting a followup to my original post because YES I'm still having trouble with this mower. It has been nearly a year since my last post and little has changed. After my last post i borrowed a nieghbors mower until i decided what to do..just for a couple weeks. I decided to try cleaning the tank/carb once more before just buying a new carb altogether. This time I used compressed air (i didnt have any the other times) Well the mower ran fine for at least a month and it seemed like problem was hesitation, surge, etc. It all came back again around 5 weeks later and I'd end up cutting the front no problems. Then in the back it would die about halfway through..restart after 5 minutes, so I just dealt with it At this point only to cut a few more times anyways. So I drain the gas for the winter and first cut this year (new plug, oil, gas, filter) it started on the second pull. I knew the problem was still there but gave it a go anyway. It cut the front yard fine in about 6 minutes or so no problems. To the back and its the same scenario as before and still no start when hot. Well after scouring various webites i read good things about some stuff called "PB Lawnmower tune up" and decided to give it a try before just chuckin the old carb and getting a new. Supposedly its supposed to emulsify any dirt, sludge, etc and free clogged passages. I sprayed it in spark plug hole, started engine let run for 5 minutes, repeat... Afterwards changed oil. Well no change, started fine, ran for almost 5 minutes..then died. I am officially stumped right only other explanation would be the coil but on a mower barely 3 years old I can't see how thats possible. I would think I'd have more starting problems than anything? There isnt any evident problems with the wires that I've noticed and I would like to narrow it down to one or the other (carb or coil) but not both..just seems ridiculous for a otherwise excellent performing engine. The Engine's model number is 12Q802.

    Bookmark   May 9, 2007 at 5:02PM
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I hate to tell you, but spraying cleaner in the sparkplug hole will do nothing for the carb. In order for some solvent to clean the passages in the carb, it will have to be mixed with the gas. Spraying down the air intake will do little for it either. If it runs fine cold and then dies after it heats up, then runs fine again when it cools off, and it does this repeatedly, I'd say it has to be the coil.

    Bookmark   May 9, 2007 at 5:22PM
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Check for spark IMMEDIATELY after engine dies!

    Bookmark   May 9, 2007 at 6:09PM
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Does anyone know if there's a way to test the coils on this engine? I have a multimeter so it would be nice if i could test it before buying a new one.
Briggs Quantum
Model: 12Q802
Type: 0202B1
Code: 02062758

    Bookmark   May 10, 2007 at 11:22PM
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Well, since cleaning the carb seemed to work for 5 weeks, I'd try that again.

MANY coils/modules are fine when they are cold, but die when they are HOT!

If you still have the old spark plug, open the gap to about .075" or so.
When the mower dies, swittch the plug wire to that plug, ground it to the engine block and give it a pull. If you have spark, the coils good.
You might even try it before you mow, just to make sure you can get a spark then.

    Bookmark   May 10, 2007 at 11:48PM
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I have the same problem with the starting then dying after a few seconds....BUT, if I continue to pour gas into the carb, it runs great until the gas runs out...???? HELP!

    Bookmark   August 12, 2011 at 3:35PM
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I've been a mechanic for over 35 years and my father was a master mechanic. I've worked on everything from lawn mowers to heavy equipment, gas and diesel. The internal combustion engine basically needs three components to run, fuel, air, gets much deeper from the mechanics perspective but this is sufficient knowledge for the do-it-yourselfer!
One fella on here says his engine will run if he keeps dumping gasoline in the carburator which should have told him right from the get go that its either plugged or leaking fuel lines or the carburator diaphram has a hole in it. Not much else can cause that problem other than being out of fuel or starving for fuel.
The spit and sputter/stalling issue depends upon the engine but in general, I would be looking at fuel feeding the carburator to make sure it is clean, not contaminated, and in sufficient supply. Outside of that, I would be looking for an electrical issue. If you have cam, valve, or other issues, the thing will either not run at all or very erratic all the time, so that eliminates those issues in my opinion.
Depending on the engine whether or not any electronics are involved like the Inteks, you have an electrical safety shut off on the bottom of the carb that shuts the fuel off when the key is off to prevent fuel from leaking and causing fires. You also have a bunch of safety switches such as the seat, brake/clutch pedal etc. Anyone of those items can cause the run/stall with the most emphasis on the carb shut off. There's a plunger in there that can varnish and stick and will for surely cause that erratic running behavior. Many of these switches are comparitable to "idiot guages" on your vehicle for people who don't understand how to interpret full guage readings. The idiot gauge uses a light, red light means even though most interpret it to continue driving till it pukes!
I always maintainence my equipment on a regular schedule changing filters, fluids, etc which prevents many of these issues.If a hose or line looks frayed or damaged, heat cracked, etc............change it before it becomes a major event! GOOD PM is mans best friend!!!

    Bookmark   November 4, 2011 at 7:46AM
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Scotts Riding Mower w/25HP Briggs Intek. Hard start and surging then just dies out. I have had issues with this for a long while. It normally went away when warmed up. Now I could not keep it running. It would run if I kept spraying in starting fluid. But then just stop abruptly. Did carb cleaner; same. I was reading up on governor issues, so I went out and spayed aerosol "dry" lubricant all over the gov. & linkages twice. It started and ran perfectly now. Seems like that was the issue. The gov. was not responding properly to keep it running. I have not used for a job yet, so I will see if that really cured it...

    Bookmark   March 27, 2012 at 12:43PM
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