John Deere starting problem

[langod]

Having a problem starting my JD riding mower.
2 cyl, 18hp engine, cranks and cranks and cranks, but won't start. Battery is bad, so I have to start it on a charger/booster -- but it's been that way all summer and has always started.

Changed plugs and air filter.
Pulled plugs and held them against chassis while cranking, could see spark.
Smell gas from carb.
Occasionally pops/puffs from carb.

What am I missing?

 

[mikewood]

Silly question but does it have a seat kill switch? Some tractors won't start or run if you are not sitting on the seat. You Might tear down and clean the carb. Did you get the wiring on the plugs crossed? Try a new battery. Some electronic start machines don't like "external power".

 

[eastomjac]

which engine does it have?will it turn over?

 

[Dusty1]

Could be many things. Try starting it with the air cleaner off and try the choke in a few positions. Dont crank too long at one time ie 20 seconds a couple of times then wait 5 min. If that doesn't work, give a small sprits of starting fluid to the carb while cranking. Most of the time this works for me. Good luck.

 

[langod]

Kill switch is OK (else it wouldn't crank.)
Plug wires -- hmmm. Maybe I'll try replacing them, plugs are sparking, but the wires are the originals and the tractor is about 8-9 years old.

Forget the exact engine. It's a "twin" Briggs and Stratton with 20hp. (not 18) (edit - here: http://www.tractordata.com/lawn-tractors/000/0/0/9-john-deere-125-engine.html)
Engine cranks, but doesn't catch. After extended cranking, I can smell gas from the carb with the air cleaner off.

Been trying that -- haven't tried starter fluid.

Is there such a thing as "not enough spark"? I mean, I can see the plugs spark, but maybe it's not powerful enough -- do I need to look into wires, distributor, points (I assume it has them as opposed to electronic)

 

[PugslyCat]

Is it a matter of needing more choke in the cool weather?

Consider cleaning the plugs with a wire brush or replacing them at that age. It sounds like if you pull the plug out of the cylinder but leave it wired you see a spark as you crank it. That has me thinking it's a fuel issue and not a spark issue, but if you have the plug out you might as well clean it and gape it.

Have you tried a new fuel filter? Those are pretty cheap and easy to replace.

While you have the fuel filter off can you crank it and see if gas comes out? My L120 has some gunk in the tank and sometimes plugs up. Also if you have water in the gas that might be a chance to get some of it pumped out.

Is there any chance of fuel contamination? I wound up with a tank full of diesel fuel once. Drained the tank and refilled with gasoline and it did OK with no damage.

 

[eastomjac]

dont try starter fluid its way too dry.it will damage your engine.try carb cleaner instead.problem sounds to me like a carb diaphram.after you try to crank it see if your plugs are wet or dry.too wet flooded,too dry not getting fuel.if the plugs are sparking it not a fire prob.which carb do you have?it should have a diaphram pump on it somewhere.the rubber in these pumps goes bad more often than you think.odds are good this is it.

 

[Dools]

In 2012 I got a new lawn tractor.

Before that, I was trying to keep my 1978 JD 300 with a newer 315 deck going.

I joined mytractorforum.com

I got answers. They, Like BB, for shaving, Know Their Stuff.

I wish you well.

 

[langod]

Thanks for all the suggestions. I intended to work on it last night, but other things got in the way and wasn't able to f- with it. I think Eastom Jac is on the right track with the carb. The other day when this all started, I pulled the old plugs to check them and they were dry. Other than replacing oil and filters, I haven't done any maintenance to this machine since I bought it in '06 or so. Obviously needs a battery, probably plug wires and points.
I may just call up the local dealer and have them come get it and do a full maintenance on it. 'Course it would be good to get it to run at least once first so i can cut the lawn -- it's about 6" tall.....

 

[Winchester38]

Checked compression?

Smell the oil. If it smells gassy, it may have flooded badly when you tried to start it originally, the gas may have washed the cylinder walls (decreased/poor compression), and now it won't start due to low compression. If the oil is gassy smelling, change it, and pour a teaspoon full into each plug hole (should bring the compression back up if that's your issue).

Had this exact problem with a motorcycle a few seasons back. Was changing plugs, filters, coils, oil, wires, ECU's, gas, etc before I realized I hadn't checked compression.

Air + Spark + Fuel + Compression = Fire

 

[langod]

Checked compression?

Smell the oil. If it smells gassy, it may have flooded badly when you tried to start it originally, the gas may have washed the cylinder walls (decreased/poor compression), and now it won't start due to low compression. If the oil is gassy smelling, change it, and pour a teaspoon full into each plug hole (should bring the compression back up if that's your issue).

Had this exact problem with a motorcycle a few seasons back. Was changing plugs, filters, coils, oil, wires, ECU's, gas, etc before I realized I hadn't checked compression.

Air + Spark + Fuel + Compression = Fire

That was it! Thanks very much!
Oil was gassy smelling, so I put some oil in the cylinders and it started right up!
Excellent!
Got to change the oil now -- I'm sure the oil is completely ruined.

 

[August West]

That was it! Thanks very much!
Oil was gassy smelling, so I put some oil in the cylinders and it started right up!
Excellent!
Got to change the oil now -- I'm sure the oil is completely ruined.

Another B&B miracle!

 

[Winchester38]

That was it! Thanks very much!
Oil was gassy smelling, so I put some oil in the cylinders and it started right up!
Excellent!
Got to change the oil now -- I'm sure the oil is completely ruined.

Glad to hear it! Make sure you get the old oil out ASAP!