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Changed blades and won't start!


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05-22-10, 06:31 PM   #1  
Changed blades and won't start!

I changed the blades on my 6 year old Murray 17.5 HP 42" lawn tractor today. I was pushing the deck back under the machine and gas started suddenly dribbling onto the ground from the carburator near where the air intake attaches. It stopped after a few seconds and I cleaned it up, but something's wrong (not from the fuel line). I must have hit a wire or something because it turns over briefly, won't start, the starter is clicking sometimes, and now there's a fried electrical smell and some sparks coming from the area under the ignition switch.

So I now have sharp blades but a mower that won't go!

Where to start with this problem?

 
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05-22-10, 10:24 PM   #2  
Sounds like the mower maybe was tipped? If not, the carb is leaking. You have gas in the cylinder, keeping the piston from moving which likely burned up the starter solenoid from trying to crank the engine. Remove the plug, tie the plug wire back where it can't spark against metal, and turn the engine to expel the gas from the cylinder. There is probably gas in the oil, so drain it and refill, and fix the leaking carb (probably needs cleaning unless you had it tipped). The air filter may be soaked w/gas too.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

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05-23-10, 02:59 AM   #3  
Tractor wasn't tipped. It was more like something opened and released the fuel. Like I say, it was just sitting there while I pushed the deck under. Air filters are not soaked. I rebuilt the carb last year so I'll check the bolts and clean it and change the oil.

Are you saying the starter needs to be replaced? Last try (jumped to my pickup) it wouldn't even turn over.

 
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05-23-10, 11:32 AM   #4  
I guess I need some help here. I'm getting a single click (more like a soft clunk) in the compartment under the ignition/dash when I turn the ignition switch . Engine isn't turning over.

Model is B&S 31C707.

Where is the solenoid?

Thanks!

steve

 
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05-23-10, 10:02 PM   #5  
The solenoid is under the seat, in front of the battery (Where the positive/red wire goes to from the battery). If you briefly jump the wire from the positive (Where the said cable bolts to) to what I believe is a smaller post (Where the starter cable goes to) this may help and if it starts, the starter should be fine and the solenoid is fried. You can also just take a jumper cable from the positive battery post to the starter post where the positive cable attaches. Make sure there is none of that gas leaking out because there should be a few sparks emitted.

And as for the carb... maybe when you hit a wire the fuel shutoff solenoid opened (on the bottom of the carb) and fuel dribbled out for that reason. But you do want to expel that so the cylinder wall is lubricated with oil and not gas.

Hopefully this helps you!

 
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05-23-10, 11:19 PM   #6  
Funny little side note..

I have put the 'curved' blades on my mower upside down by mistake. on the up side it will now (set on the lowest cut) plow my new garden beds... Sweet little mistake...


Last edited by the_tow_guy; 05-24-10 at 05:23 AM. Reason: Removed link.
 
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05-24-10, 07:14 AM   #7  
This will teach me to figure out one problem before cranking away. I'll move on with the starter diagnosis. Thanks for the hints!

BTW, I have a B&S repair manual, an illustrated parts list, and two owner's manuals for the tractor and the engine, but none of these tells me where the solenoid is or even what it looks like!

I don't mind working on the engine but life is a lot easier with the right reference books. Is there a great resource I should know about for working on this and other B&S engines?

 
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05-24-10, 08:03 AM   #8  
The solenoid is part of the mower and will not be included with literature for the engine and doubtfully the owners manual for the mower.
If you are getting a click or clunk, chances are you have a bad ground.
You can run a test lead or one cable of a jumper cable from the negative battery post to one of the starter mounting bolts. If it starts then this should confirm a bad ground and you will need to follow the leads out and clean the grounding points, including where the solenoid mounts to the frame.
If you follow the positive battery lead, the first connection should be to the post on the solenoid.

 
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05-25-10, 05:57 PM   #9  
OK, I tried both methods of bypassing the solenoid (jumping across the solenoid terminals and jumping from the positive battery post directly to the positive terminal on the starter). (BTW, I ***think*** this is the starter - it's cylindrical and black and the red lead from the solenoid is bolted to it. It's another thing I can't find a diagram of attached to the engine),

Anyway, when I do either of these two things the engine cranks once or twice very reluctantly but doesn't start. (The jumper cables get very hot though).

Does this mean the solenoid is gone? Does it say anything about the starter?

 
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05-25-10, 06:52 PM   #10  
You never said you did anything to get the fluid out of the cylinder, so I assume you haven't? You're going to have to get the gas or oil or whatever out of the cylinder or you'll wind up burning up your $110 starter along with that solenoid.


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05-25-10, 07:44 PM   #11  
OK, I was assuming it would have evaporated since Saturday Not? Anyway, the original instructions were to "turn the engine to expel the gas from the cylinder." It's been turned several times since then. Or do I need to do this with the plug removed?

I disregarded the bit about gas in the oil because the tractor had not been tipped.

BTW, the solenoid is in the compartment under the steering wheel, not under the seat . . .

 
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05-29-10, 04:04 AM   #12  
Sounds like your engine is hydro-locked. IE the cylinder is full of fuel. You need to pull the spark plug(s) and crank the engine to expel the gas. Keep the plug wires away so the spark doesn't ignite the gas. Sounds like the starter is still ok but the solenoid may be fried. If she turns over freely, using the starter, with the plugs out the starter is ok. If you have to by-pass the solenoid to get it to crank, replace the soleniod.

 
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05-29-10, 12:18 PM   #13  
Thanks, I did all that, changed the oil, and replaced the solenoid, and she's starting and running great.

What I don't get is:

(a) how the cylinder got full of fuel, and
(b) how fuel got into the oil

All this happened when I changed the blade!

 
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05-29-10, 01:14 PM   #14  
Coincidence. Your carburetor leaked and needs to be cleaned to keep it from happening again. It may be slowly doing it now as we type.


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05-30-10, 06:11 AM   #15  
Thanks for your help. Can you go into just a bit more detail on what you mean by "cleaned"? Spray it with carb cleaner?

 
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05-30-10, 01:06 PM   #16  
Take the bowl off and see if there is trash/rust/water in it. If so, clean the bowl well, remove the float and needle, clean the seat area where the needle goes well with carb spray and a q-tip, and clean the needle as well, and if the needle shows signs of wear at the tip, replace it.


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05-30-10, 01:21 PM   #17  
It turns out you're right - it was leaking as we wrote! It sat for two days and when I tried to start it just now it cranked once then gave the soft clunk. I took the plug out and gas sprayed forward like a pressure washer. After ejecting, it started fine.

 
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05-31-10, 08:09 AM   #18  
OK, carb has been thoroughly cleaned but now I seem to be back with electrical problems.

Now I only get a soft high-pitched squeal under the dash when I turn the key, but the engine doesn't turn. Battery tests OK. I tried jumping across the (new) solenoid and jumping from the pos battery terminal to the pos starter terminal, but I get nothing but sparks.

Three questions:

1) I tried removing the plug to eject any gas remaining in the cylinder but haven't been able to get it to turn over. So bottom line is I have no way to eject any gas, evaluate whether cleaning the carb helped the gas leak, or even see if the carb works now. Is there a way to push-start?

2) Is there a way to tell if the carb is still leaking without cranking the engine?

3) Is the starter gone now?


Last edited by suobs; 05-31-10 at 08:36 AM.
 
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05-31-10, 08:54 AM   #19  
See if you can spin the engine by hand. Either from the top or using the pulley underneath.
It could be the starter is engaged with the flywheel binding it...usually you can get it to drop out spinning by hand.
Leave the spark plug out to make it a bit easier.

 
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05-31-10, 09:22 AM   #20  
Can't get it to budge with the pulley. Not sure how I would do it from above.

What does that tell me?

 
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05-31-10, 09:45 AM   #21  
Have you changed the oil since it has been diluted and overfull of fuel?
If it was ran with the oil in that condition for any amount of time it could have suffered damage.
It is still likely the starter is engaged and binding, you might need to pull the starter to dislodge it, and you can test it while it is off.
If with the starter removed it still will not turn, then you could have other issues...I would begin with the starter though.

You can use jumper cables to test the starter while removed. Ground from battery to mounting ears of starter, then touch positive from battery to terminal on starter and it should kick out and spin.

 
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05-31-10, 10:30 AM   #22  
Yes the oil was changed. It started then I cleaned the carb. Could gas have got back into the oil? Sniffing the dipstick now, there's a slight smell of gas but nothing like before.

I'm still unclear about how gas gets into the oil. Does this happen when running or stopped or both?

 
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05-31-10, 10:53 AM   #23  
More so when stopped than running. When running it usually burns or consumes enough to keep the bowl level down. When not running the bowl overfills and leaks into the intake and eventually into the sump of the engine.

 
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06-01-10, 07:11 PM   #24  
Posted By: suobs Thanks, I did all that, changed the oil, and replaced the solenoid, and she's starting and running great.

What I don't get is:

(a) how the cylinder got full of fuel, and
(b) how fuel got into the oil

All this happened when I changed the blade!
I re-ringed an engine this spring that sat apart all winter. Carb bowl was checked to be clean when I reassembled. I lent it to a friend for a few weeks then brought it home and used a few times. One morning the garage smelled of gas and I checked and I had not closed the fuel shutoff and area around carb was wet with gas. Hadn't got into crankcase yet. I pulled bowl and found brown crap and a water blob. Either my friend or I used crappy gas. Fuel line has a filter too.

 
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06-02-10, 05:00 PM   #25  
OK, so I started to remove the starter. First thing I noticed is it seems to be impossible to access the bolts that hold it on. They're pretty much behind the starter. Any clues on that would be appreciated.

Second thing was the gear on top of the starter only overlapped the big gear on the engine (flywheel?) about 1/8". As I poked around removing the positive batter terminal and trying to figure out the mounting bolts, the starter gear slipped down further and is now disengaged from the engine gear, like the shaft slipped. There's a also a white area under the starter gear with a spring on it that looks squeaky clean (like it wasn't exposed before). Both the starter and engine turn easily now.

So I'm thinking at least the engine isn't seized up or something?. And way the starter gear is just flopping up and down and doesn't seem to be in position to engage the engine gear, I should remove the starter, test it, and maybe get a new one? Altho there seems to be something mechanical wrong with it.

Anyway I would appreciate any insights and also some advice on getting at those mounting bolts.

 
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06-02-10, 05:42 PM   #26  
Your description of the starter gear sounds normal. It was just jammed. It happens from time to time. I suspect it will work fine now, and I wouldn't mess with it unless there is something obviously wrong with it.


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06-06-10, 07:25 AM   #27  
Thanks for all the help. But if it's been sitting a day it will start only after I eject gas (a pretty good gush) from the spark plug hole. So I take it the carb is still leaking fuel. You'll recall the carb has been cleaned.

Two questions:

1) Should I just buy one of those carb rebuild kits, or can someone point me to a specific likely cause of gas leaking into the cylinder when it's not running?

2) Will gas get into the oil every time this happens? How would I know before starting? The oil has a very slight gas smell but there's nothing I can see on the dipstick. In other words since I haven't fixed the carb problem yet, can I mow this afternoon after ejecting the gas, or do I need to change the oil again before starting up? Or should I just not run it at all?

 
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06-06-10, 08:14 AM   #28  
If you are confident you cleaned the carb well, including removing the float and needle and cleaning the seat...and it is still leaking then it still needs to be fixed. Carb overhaul kit should have a new needle, if it is rubber tipped then the seat can be polished a bit as cheese mentioned with a Q-tip and some polishing compound or some sort of mild abrasive cleaner. cheese usually puts the Q-tip in a drill, IIRC.

The engine should not be ran if the oil is overfull or diluted with gas. Pre mature wear and or seizure can result.

 
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06-06-10, 08:28 AM   #29  
The tip of the needle is black, but I'm not sure it's rubber. I wiped it off with a q-tip and carb cleaner but I didn't know about the polishing compound trick at the time.

I don't know what the seat is. Is it the hole the needle goes into pointy end first? And you're saying to insert a q-tip into the hole with like, brass cleaner or something on it and spin with a drill?

The oil does not appear to be diluted although I'm still not clear on how I would know if it is. Should I just figure it is from the smell? Is a mild smell of gas on the dipstick normal?

 
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06-06-10, 09:04 AM   #30  
Posted By: suobs The tip of the needle is black, but I'm not sure it's rubber. I wiped it off with a q-tip and carb cleaner but I didn't know about the polishing compound trick at the time.

I don't know what the seat is. Is it the hole the needle goes into pointy end first? And you're saying to insert a q-tip into the hole with like, brass cleaner or something on it and spin with a drill?
Try and indent the tip on the needle with your fingernail, you can feel it. This rubber tip seals on the seat at the end of the hole it goes into. Look into it and see if the seat is damaged or....??? Then clean it up to be sure.
If your fuel system is gravity feed, or the fuel pump is seperate from the carb, there is an easy bench test you can do to make sure the needle and seat are not leaking.

Posted By: suobs The oil does not appear to be diluted although I'm still not clear on how I would know if it is. Should I just figure it is from the smell? Is a mild smell of gas on the dipstick normal?
It's pretty much your call. If it has a distinct smell of gas, I would change it. If the level hasn't changed much or at all I might go ahead and do the carb, bench test it, put it back and make sure it is going to run...then before putting it back in normal service, change the oil one last time.

 
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