Lawn and Garden forum - Need Briggs troubleshooting info

Author

Need Briggs troubleshooting info

Roger Blake

2006-05-13, 5:21 pm

I was mowing the lawn today with our MTD garden tractor when it suddenly
and without warning started sputtering and died. The engine is a 14.5 HP
Briggs & Stratton OHV job with electric start.

I checked for obvious stuff like clogged fuel and air filters, and cleaned
the spark plug (it had some carbon deposits). Still no good, the engine
barely catches even with the throttle wide open, backfires through the
carb, and dies. On a car I'd say it sounded like it was trying to run
with severely retarded ignition timing, or too lean a mixture, but I'm
not quite sure what to test on this thing. (This is a 1996-vintage mower,
so I'm pretty sure it has transistorized ignition, not points.) Maybe
some dirt got past the fuel filter into the carb? Any "gotchas" to
be aware of in taking the carb apart?

Any pointers on what to check, or to troubleshooting/tech info online
would be greatly appreciated!

--
Roger Blake
(Subtract 10 for email.)

GrtArtiste

2006-05-13, 7:21 pm

An engine model/serial number might help with this. You could also try
the Small Engine Technical Forum at http://www.perr.com/forum/ Some
very knowledgeable people there.

GrtArtiste

Roger Blake

2006-05-14, 1:21 am

In article <1147555359.223531.178150@i40g2000cwc.googlegroups.com>, GrtArtiste wrote:
> An engine model/serial number might help with this. You could also try
> the Small Engine Technical Forum at http://www.perr.com/forum/ Some
> very knowledgeable people there.

Thanks for the lead on the tech forum, I'll check it out. The engine
has a metal plate with the following info:

MODEL: 287707
TYPE: 0224 01
CODE: 9603044A

--
Roger Blake
(Subtract 10 for email.)

jim.blakely

2006-05-14, 1:21 am

"Roger Blake" <rogblake10@iname10.com> wrote in message
news:slrne6cfb2.5fs.rogblake10@moog.netaxs.com...
> I was mowing the lawn today with our MTD garden tractor when it suddenly
> and without warning started sputtering and died. The engine is a 14.5 HP
> Briggs & Stratton OHV job with electric start.
>
> I checked for obvious stuff like clogged fuel and air filters, and cleaned
> the spark plug (it had some carbon deposits). Still no good, the engine
> barely catches even with the throttle wide open, backfires through the
> carb, and dies. On a car I'd say it sounded like it was trying to run
> with severely retarded ignition timing, or too lean a mixture, but I'm
> not quite sure what to test on this thing. (This is a 1996-vintage mower,
> so I'm pretty sure it has transistorized ignition, not points.) Maybe
> some dirt got past the fuel filter into the carb? Any "gotchas" to
> be aware of in taking the carb apart?
>
> Any pointers on what to check, or to troubleshooting/tech info online
> would be greatly appreciated!

Roger,
If by chance you hit something, the key could have sheared (completely or
partially) and then the timing will be off. You can pull the starter cover
and look at the flywheel to check.

Stubby

2006-05-14, 1:21 pm

jim.blakely wrote:
> "Roger Blake" <rogblake10@iname10.com> wrote in message
> news:slrne6cfb2.5fs.rogblake10@moog.netaxs.com...
>
> Roger,
> If by chance you hit something, the key could have sheared (completely or
> partially) and then the timing will be off. You can pull the starter cover
> and look at the flywheel to check.
>
>
A compression test will tell if it is a burned valve.

Roger Blake

2006-05-14, 4:21 pm

In article <-uWdnfP4mJXzyfrZRVn-uA@comcast.com>, Stubby wrote:
> A compression test will tell if it is a burned valve.

Compression is 100 psi, which would be low for an automotive engine
but I'm going to guess is pretty much OK in this application.

I pulled the carb off, it is a side-draft Walbro that has a dome-shaped
sheet metal fuel bowl with what looks like a solenoid (fuel cutoff?) on
the bottom. How do I get the fuel bowl off to get inside? I don't see
anything obvious and don't want to force/break anything.

--
Roger Blake
(Subtract 10 for email.)

glyford@gmail.com

2006-05-15, 6:21 pm

Roger Blake wrote:
> In article <-uWdnfP4mJXzyfrZRVn-uA@comcast.com>, Stubby wrote:
>
> Compression is 100 psi, which would be low for an automotive engine
> but I'm going to guess is pretty much OK in this application.
>
> I pulled the carb off, it is a side-draft Walbro that has a dome-shaped
> sheet metal fuel bowl with what looks like a solenoid (fuel cutoff?) on
> the bottom. How do I get the fuel bowl off to get inside? I don't see
> anything obvious and don't want to force/break anything.

Unscrew the solenoid.

mowpaul321

2006-05-17, 12:21 am

If the engine fires then stops or flutters it's not electrical, solenoid
etc.
Although a spark plug can fail best to try a new one

If it was that or a flat battery it wouldn't turn over on the key
start

If it was the coil you wouldn't get anything out of it at all they
either work or they don't.
Unlikely to be the key because you have to give it a good wack and the
only connection is through the belts?

Compression failure is not very common on something of that age. Unless
you use it commercially.

Fuel is the most common problem. As long as the fuel is comming out of
the inlet there's no need to worry about the float. Remove the main jet
out of the centre if there is a slot in it & clean out with an airline.
If not it's fixed so you just spray up the middle as best you can. (use
a piece of wire to clean as last resort) Take out and spray any mixture
jets if it has them. Hold float & needle secure in carb while spraying
to avoid loosing any seat from the inlet.

Also check the springs & throttle linkage make sure of no damage.

If no luck it might be best to get a new carb, they can wear up
especially on newer types or a carb kit if you have a mixture screw &
replaceable jet(s)

Dealers need the nos stamped on the top or about the side of the engine
cowling for spares. Nearest dealer can be found at
http://tinyurl.com/mhuo9

e.g. 217900 0125 E1 96258674

jim.blakely Wrote:
> "Roger Blake" rogblake10@iname10.com wrote in message
> news:slrne6cfb2.5fs.rogblake10@moog.netaxs.com...
> I was mowing the lawn today with our MTD garden tractor when it
> suddenly
> and without warning started sputtering and died. The engine is a 14.5
> HP
> Briggs & Stratton OHV job with electric start.
>
> I checked for obvious stuff like clogged fuel and air filters, and
> cleaned
> the spark plug (it had some carbon deposits). Still no good, the
> engine
> barely catches even with the throttle wide open, backfires through
> the
> carb, and dies. On a car I'd say it sounded like it was trying to
> run
> with severely retarded ignition timing, or too lean a mixture, but
> I'm
> not quite sure what to test on this thing. (This is a 1996-vintage
> mower,
> so I'm pretty sure it has transistorized ignition, not points.) Maybe
> some dirt got past the fuel filter into the carb? Any "gotchas" to
> be aware of in taking the carb apart?
>
> Any pointers on what to check, or to troubleshooting/tech info online
> would be greatly appreciated!
>
> Roger,
> If by chance you hit something, the key could have sheared (completely
> or
> partially) and then the timing will be off. You can pull the starter
> cover
> and look at the flywheel to check.

--
mowpaul321

Roger Blake

2006-05-17, 12:21 am

In article <mowpaul321.27xiw5@gardenbanter.co.uk>, mowpaul321 wrote:
> If the engine fires then stops or flutters it's not electrical, solenoid
> Although a spark plug can fail best to try a new one

I have not had time to get back to it yet, the engine does run, but
just barely and spits back through the carb.

I've purchased the B&S book "Small Engine Care & Repair" which has
a fair amount of detail on the carb and ignition system. I need to
scout up a thin wrench to get the solenoid off the bottom of the
carb so I can at least clean the jets etc. in there. (I've already
put in a new spark plug.)

--
Roger Blake
(Subtract 10 for email.)

Roger Blake

2006-05-17, 5:21 pm

Today I pulled the carb apart to clean it, though it was pretty much
spotless inside. Didn't make much of any difference in the way the engine
runs, it's still weak and backfires through the carb on every crankshaft
revolution. I also pulled the big bolt that holds the flywheel in place
and the key looks OK, no sign that it has sheared, everything lines up.
(Anyone know the torque spec for that bolt?)

So to summarize:

* Engine barely runs, backfires out carb on each crank revolution
(puff of air accompanied by loud 'pop')
* New spark plug
* New gas & air filters
* Carb cleaned
* Compression is approx. 100 PSI
* No sign of shearing on flywheel key.
* Solenoid on carb works OK (clicks with ignition, also tested off carb)

Symptoms seem to be that of late ignition timing, but I don't see any obvious
adjustment for that. Any ideas on the next logical troubleshooting step?

--
Roger Blake
(Subtract 10 for email.)

Roger Blake

2006-05-17, 7:21 pm

On a suggestion in the perr.com forum, I removed that valve cover
and found that the stud for the topmost valve had vibrated out
and was partway unscrewed from the cylinder head! This of course royally
screwed up the valve timing. I've tightened it down (fortunately it does
not seem to be stripped) and will see how the engine runs after checking
valve clearance...

--
Roger Blake
(Subtract 10 for email.)

GrtArtiste

2006-05-17, 8:21 pm

Good to hear that you are making progress. Keep asking those forum
folks questions, and you'll keep getting answers. It makes for
interesting reading, even if you don't need help with a problem.Another
place I go to with lawnmower/snowblower info is www.opeonthenet.com

GrtArtiste

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