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I have a lawn-boy, model# 10670c, which can not start.
I changed oil, spark plug this spring. It worked well. 3 weeks before, it sill worked well. But now, it could not start. I cleaned carburetor, replaced with new air filter. Still cannot start it.
Recently, I bought a new ignition (34443D, solid state ignition). After installation, it still can not start. What else I can do? Please help.

Mower can not start - 10670c model

Merged two threads.

Fresh gas, air, spark, & compression are needed to start.

Just what he said and add correct timing into the mix.

Time to clean and rebuild the carb using this kit, 631021B, about $5.00. Here is the procedure I use.
[FONT=&quot][FONT=&quot]Needle and seat replacement.[/FONT][/FONT]
[FONT=&quot][FONT=&quot][/FONT]
[/FONT]
[FONT=&quot][FONT=&quot]Remove the carb, and then remove the float bowl. Check the float bowl jet (which is the bowl screw) and make sure the jets both horizontal and vertical are clean and open. Tip the carb upside down and remove the float pin and float with needle attached. Look in the float needle passage and you should see the red float seat at the bottom of the passage. This is where a #5 crotchet hook would come in handy as you need to remove this seat. If you have no hook, but compressed air, you can blow through the fuel inlet and try to pop the seat out. Put your thumb over the passage to prevent the seat from flying who knows where. No air or hook try bending a stiff paper clip to dig the seat out.[/FONT][/FONT]
[FONT=&quot][FONT=&quot][/FONT]
[/FONT]
[FONT=&quot][FONT=&quot]I would either give the carb a good 24 hour soaking or have it ultrasonically cleaned at this time.[/FONT][/FONT]
[FONT=&quot][FONT=&quot][/FONT]
[/FONT]
[FONT=&quot][FONT=&quot]With the seat out clean the passage way with carb cleaner. Now you must find a drill bit slightly smaller than the passage way, to be used to press in the new seat. Apply a very, very small amount of a very light lube to the new seat. 3-1 oil or lighter, to help seat it better. Carefully insert the new seat in the passage way with the rings on the seat down toward the carb body. Slowly and carefully force the seat down with the back end of the drill bit. Once it is seated, check to see that it did not flip and the rings are up. Next check to make sure that the float does not have any liquid in it. If it does, replace. If everything looks correct, attach the new needle to the float and install with the float pin centered. It everything is correct, the float should seat level to the carb body, when looking at it upside down. If everything looks good reattach the float bowl, making sure that both the bowl gasket and the nut gasket seal properly. Reinstall on the engine and test unit. Remember to have patience and take your time. Good luck, but I don't think you'll need it.[/FONT][/FONT]
[FONT=&quot][FONT=&quot][/FONT]
[/FONT]
[FONT=&quot][FONT=&quot]PS: On the side of some Tecumseh carbs you will find a plastic cover. Under this cover will be an idle jet. Remove it and check to see that the jet is open both horizontally and vertically. You should be able to push the old float needle wire through the vertical opening.[/FONT][/FONT]

Rivets said:

Time to clean and rebuild the carb using this kit, 631021B, about $5.00. Here is the procedure I use.
[FONT=&quot][FONT=&quot]Needle and seat replacement.[/FONT][/FONT]
[FONT=&quot][FONT=&quot][/FONT]
[/FONT]
[FONT=&quot][FONT=&quot]Remove the carb, and then remove the float bowl. Check the float bowl jet (which is the bowl screw) and make sure the jets both horizontal and vertical are clean and open. Tip the carb upside down and remove the float pin and float with needle attached. Look in the float needle passage and you should see the red float seat at the bottom of the passage. This is where a #5 crotchet hook would come in handy as you need to remove this seat. If you have no hook, but compressed air, you can blow through the fuel inlet and try to pop the seat out. Put your thumb over the passage to prevent the seat from flying who knows where. No air or hook try bending a stiff paper clip to dig the seat out.[/FONT][/FONT]
[FONT=&quot][FONT=&quot][/FONT]
[/FONT]
[FONT=&quot][FONT=&quot]I would either give the carb a good 24 hour soaking or have it ultrasonically cleaned at this time.[/FONT][/FONT]
[FONT=&quot][FONT=&quot][/FONT]
[/FONT]
[FONT=&quot][FONT=&quot]With the seat out clean the passage way with carb cleaner. Now you must find a drill bit slightly smaller than the passage way, to be used to press in the new seat. Apply a very, very small amount of a very light lube to the new seat. 3-1 oil or lighter, to help seat it better. Carefully insert the new seat in the passage way with the rings on the seat down toward the carb body. Slowly and carefully force the seat down with the back end of the drill bit. Once it is seated, check to see that it did not flip and the rings are up. Next check to make sure that the float does not have any liquid in it. If it does, replace. If everything looks correct, attach the new needle to the float and install with the float pin centered. It everything is correct, the float should seat level to the carb body, when looking at it upside down. If everything looks good reattach the float bowl, making sure that both the bowl gasket and the nut gasket seal properly. Reinstall on the engine and test unit. Remember to have patience and take your time. Good luck, but I don't think you'll need it.[/FONT][/FONT]
[FONT=&quot][FONT=&quot][/FONT]
[/FONT]
[FONT=&quot][FONT=&quot]PS: On the side of some Tecumseh carbs you will find a plastic cover. Under this cover will be an idle jet. Remove it and check to see that the jet is open both horizontally and vertically. You should be able to push the old float needle wire through the vertical opening.[/FONT][/FONT]

Click to expand...

Thanks for reply. I used carb cleaner, bowl all the holes in every parts of Carb. I believe that the Carb is OK. I could not get the spark. why?

Let’s get this straight, you said you replaced the coil, never said no spark. Did you set the coil air gap at.010? Did you install it with the kill wire terminal down? Did you check the kill wire for frays or pinching? All these will cause a no spark condition. I replied as I did assuming that you set the coil properly. You said you cleaned the carb, but did you set the float as I described in the procedure? This will also cause a no start condition.

Thanks for reply.
I replaced with a new coil bought in Amazon.ca. Using a business card to set the gap. connected the kill wire to coil just as before. Pulling many times, no any sparks. Then I suspected that coil I bought is not good.
I measure my old coil, set resistance range in 20K, High to Kill wire read 2.9. Looked like my old coil is OK. Now I am totally confused what make it not generate spark? Please help. Thanks.

Last night, I gave it a try again. Installed my old coil. took out spark plug, asked someone help hold it to the side of engine. Then I pulled, still no any sign of sparks.

Mulan001 said:

Thanks for reply.
I replaced with a new coil bought in Amazon.ca. Using a business card to set the gap. connected the kill wire to coil just as before. Pulling many times, no any sparks. Then I suspected that coil I bought is not good.
I measure my old coil, set resistance range in 20K, High to Kill wire read 2.9. Looked like my old coil is OK. Now I am totally confused what make it not generate spark? Please help. Thanks.

Last night, I gave it a try again. Installed my old coil. took out spark plug, asked someone help hold it to the side of engine. Then I pulled, still no any sign of sparks.

Click to expand...

Disconnect the “kill wire” and check for spark. Clean the flywheel..

Thanks Rivets for that in-depth review. I copied it because I try to cheat sometimes and you covered all the bases.

Ok, let’s go back to the beginning. Checking resistance on today’s coils will not result in an accurate test, due to the primary circuit containing the trigger coil. First, I don’t care which coil you test first, but I would like you to install a coil without the kill wire attached and check for spark. If you have spark the coil is good and you have a bad kill circuit. If no spark and you know the coil is installed correctly, the coil is bad. Repeat using other coil. The test for a bad kill wire is check resistance from terminal which connects to the coil and ground. Do this with the brake bail handle tied back to open the kill switch. Your resistance reading should be infinity. Any other reading indicates that the wire is grounding out with the kill switch open, causing your problem. Do all tests with a new plug. I will not be around much for the next 5 days, so if you have other questions feel free to ask and I’ll try to get back to you ASAP, but I know other techs are following this thread and may jump in. Many times we don’t like to jump on other techs threads, because it can get confusing for the original poster. Hope your next post is saying success.

Hi, first of all, thanks a lot for providing me so many test methods. I just did a test of coil with kill wire off. I asked someone hold spark plug which was inserted in coil boot connection. I pulled a couple of times, no sparks. My coil was installed properly. So this suggested that coil was bad. right? I am going to buy another coil. The one last time I bought was sent back to amazon.

I did a test with coil wire off, and pull and did not see any sparks. When I pull, I took out spark plug and connected it to coil boot. Does this suggest that the coil was bad. if yes, I am going to buy another coil. Thanks a lot for replying me. Really appricated!

Yup, deceased

Not to be a smart A, but you did ground the plug to the block when you did the test? If so agree DOA.

Rivets said:

Not to be a smart A, but you did ground the plug to the block when you did the test? If so agree DOA.

Click to expand...

I tested with a new ignition coil with kill wire off, and I saw sparks. But when I connected kill wire, no spark. So this suggested that the kill wire circle was bad. Right? My kill wire had a module switch with part# 108-0967. How to test if this one is bad or not?
Thanks so much for replying. It's close bit by bit.

Test the kill wire for continuity to the engine
In the run position it should be open circuit
In the off position it should be ground
Can't help you any more than that as Lawn Boys were never imported into Aust AFAIK.
And if they did they would not have sold well compared to the higher spec locally made mowers.

Since this coil has an internal trigger coil there is no way to test without an expensive piece of testing equipment. The test I use is the same as the one I posted earlier. From what you are saying, Bert has put you on the right track in testing the continuity of the kill wire.

Rivets said:

Since this coil has an internal trigger coil there is no way to test without an expensive piece of testing equipment. The test I use is the same as the one I posted earlier. From what you are saying, Bert has put you on the right track in testing the continuity of the kill wire.

Click to expand...

The module switch 108-0967 is a capacitance. I used a multi-meter measure it, it has 0 resistance which I believed was bad. Right now, it is hard for me to find this parts in Canada except order on line from USA side. :- (
Thanks for all replies to help me find the reason of this malfunction.

Not to be a smarty-pants, but is it CAN not start or WILL not start? BTW, even when the ignition system is working perfectly, the spark will not jump much of a gap. about .030 to .040 is about it. This is not like the ignition in your car.

Elfiero said:

Not to be a smarty-pants, but is it CAN not start or WILL not start? BTW, even when the ignition system is working perfectly, the spark will not jump much of a gap. about .030 to .040 is about it. This is not like the ignition in your car.

Click to expand...

I took out the module switch 108-0967, pulling and could start the mower. Without that module switch, it ran only for 40 seconds then it shut down. I ordered a part from USA, it would come next month. Hope that part will fix the machine. Thanks a lot to this forum. Really helpful!