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Lawnmower engine question

I can't find a lawnmower mechanic newsgroup so I'll ask it here. My neighbor, who is a woman, has a large Murray riding lawnmower that was purchased new in 2004. It has a Briggs & Stratton 14.5 hp engine with an electric starter. It sat throughout the year 2005 without being used. I recently tried to start it but it wouldn't crank all the way, acting as if it had some resistance (this is with a brand new battery that I had just installed the same day) while at the same time some gasoline began pouring out of the air intake and onto the ground. I unscrewed the spark plug and removed it from it's hole to relieve the resistance from the engine. After removing the spark plug, I tried to crank it again and it cranked very well, except that gasoline began flying out the spark plug hole at an alarming rate. I then put the spark plug back into the hole (but I intentionally left the wire off) to see if the engine could now crank against the compression, where it previously could not. The engine cranked just fine at this point so I figured that it had been binded up from sitting so long without being started. However, I noticed that when I cranked the engine with the spark plug in place that a lot of gasoline was shooting out the exhaust pipe. Because of the gasoline all over the place, I did not plug the wire back onto the spark plug for fear that the gas would ignite and catch the area on fire. It's been a couple days now and the gas has evaporated, but I an concerned that if I plug the wire back on to the spark plug and crank it, that flaming gas will shoot out of the exhaust pipe and catch something on fire. My question is; is it normal for all of that gas to have shot out of the engine under the aforementioned circumstances? Is it likely that something is wrong, or should I go ahead and put the spark plug wire on and try to start it? Thanks in advance for your guidance concerning this lawnmower problem.

Reply to
j
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Without going too carefully through your post, I am going to suggest that you are getting too much liquid gasoline in the cylinder and are getting hydrostatic lock....uncompressable liquid lock.

You will probably have to resolve the problems in the carburetor and try again. Clean out the fuel tank, rebuild the carburetor, be sure you are getting ignition, and it may well start.

Reply to
<HLS

My guess would be that the fuel pump is pumping gas straight through the carb without metering the flow correctly.

The year of non-use may have gummed up the needle and seat or the float is saturated with gas.

It's time to remove, disassemble and inspect the carb.

Reply to
anumber1

It had resistance, because the cylinder was full of liquid fuel rather than vapour. The liquid does not compress well. If you try and start an engine like this, it is VERY possible that you'll blow a ring trying to compress liquid.

I unscrewed the spark plug and

Right, because something is wrong with the carb, which is dumping liquid fuel into the cylinder rather than vapour.

I then put the spark plug back into the hole (but I intentionally left

This is because once again, there is liquid gasoline in the cylinder, where it should not be.

You need to fix the carb so that it's doing its job. I'm not familiar with the carb on that engine but I'd suggest a stuck needle. It's possible just taking the cover off, squirting carb cleaner everywhere, and making sure the needle isn't stuck and is moving freely will fix it nicely.

If it sat for a year with old gas in it, without any fuel stabilizer in it, the carb is probably very gunked up.

--scott

Reply to
Scott Dorsey

The problem is due to the gas that was in the carb dried out and turned to varnish. Often the float bowl on a Briggs like this has one big nut on the bottom. If you are lucky (note the "if")) you can remove the nut drop the float bowl down and clean it out. You should also be able to free up the float and get it working again (the float and needle valve is what shuts off the flow of gas). If your lucky this will be all that is wrong and you will be able to remove the float bowl, clean it up and reassemble without doing and further damage (like to the float or gaskets). But you really should have done that before trying to start it. You also should have sprayed some penetrating fluid in the spark plug hole before attempting to start it. If you are not lucky there will be more than this wrong. That could mean further surgery on the carb or it could be the engine is already fried due to attempting to start it after sitting so long without taking the necessary precautions. The hard cranking at first might have been due to rust in the cylinder.

-jim

j wrote:

Reply to
jim

Remove the carburetor, clean all the dried fuel additive residues from a year's worth of evaporated fuel out of the float bowl, unstick the float valve, and re-install.

And the next time its gonna sit un-used- TURN OFF THE FUEL to the carb or drain the tank to avoid ruining the carburetor again.

Reply to
Steve

Skipping the details to save space...

Stuck float valve in the carb. There ought to be a screw/bolt on the bottom of the carb bowl that will unscrew and let you remove the float bowl and the float, and clean any gunge out of/off of both, and free up the needle valve the float controls.

My bet is that the float valve is stuck in "wide open", so the engine is drawing practically straight raw gas - It then follows that the engine is going to run for crap - *IF* it manages to fire up at all.

With carbueration so screwed that it's filling the cylinder with raw gas, and spitting raw gas out the exhaust, having it run as is would be filed under "not gonna happen" in my ledger. Do a carb rebuild on it, and I bet it fires right up nicely.

Reply to
Don Bruder

I know it ain't funny to the OP, but y'know, I gotsta chuckle at 3 replies (as I type this - who knows how many more in the pipe) that, once I got to reading them after posting my response, all say the same thing, just in various phrasings: Stuck float valve - rebuild the carb.

It sould easily make one wonder how many here have been in this situation in the past... :)

:)

Reply to
Don Bruder

My very very strong suggestion is that you or your neighbor take the mower to a repair shop where the problem can be properly dignosed and corrected. Chances are it is a relatively simple fix. At the same time have the shop do a full tune-up and it will be ready to go.

Reply to
John S.

Uhhhh.... no comment :-p

Me too.

Reply to
Steve

Some of us have to clean up other peoples messes, Don;>)

Reply to
<HLS

First off.... replace the plugs, and air filter. Make sure you get all the crap out of the air filter area, then see if it will start....I've seen lawn mowers with clogged air filters that wouldn't let the mower start.... hell I had that happen to my chain saw even.... Chances are that your plugs are fouled out and if that is the case, they need replacing.

Let us know how you make out.....

Fwed

Reply to
fweddybear

Turns out this really is a good forum to post lawn mower questions. I guess most of us have had one at one time or another. I wonder why there isn't a "rec.mowers.lawns"

Kevin

Reply to
Kevin

A plugged air filter isn't his problem, a leaking needle valve is. You're right in that a plugged filter can cause it to run rich, foul the plugs and die. That isn't the problem, he's got the thing flooded so bad it won't even turn over. He needs to fix the carb, clear all that extra fuel out of the engine and probably change the oil. The plugs may need replacing but can probably just be blown dry

Reply to
Bob

Ah ha.. simple fix - sue them!! Your not the 1st to have issues with this POS cheap ass lawn mower - I'm sorry but can't help it!! My neighbor has the 2003 model and nothing but problems i.e. has cost him more in simple BS repairs than my friggin camera!

Carburator float bowel issue - only problem is they are a PITA to work on!

Reply to
Daryl Bryant

His questions lead me to belive that he has little experience in repairing motors small or large. If it has sat unused for at least a year a through going over is called for by someone with the appropriate technical skills.

Reply to
John S.

Yes, I know the carb needed work... I suppose I assumed the person asking the question realized he needed to take care of the carb too.......as someone else mentioned what to do with the carb... I guess I should have said in additon to cleaning the carb and fixing the valve.... my bad..

Fwed

Reply to
fweddybear

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