[leggot]

Hi,

I have a Craftsman 917378531. Its 7hp and a normal push mower. From what I can tell there is no spark when I pulled the spark plug out. I replaced the coil and also tested it with a multimeter and its approx 4-5k ohms. I checked the flywheel gap and its as close as possible without touching the flywheel. I checked the ground (between coil ground and flywheel) and it is about 1.5 ohms, basically very low. I cleaned off any surface rust from the coil and flywheel and I stuck the sparkplug in my edger and I can see the spark. I also set the stopper to not touch the flywheel and verified there are magnets in the flywheel.

So, I think the coil, sparkplug and ground are all good, but there is no visual spark. Is there anything else I should test, I believe I should be able to see the spark.

Thanks!

 

[tabora]

That model has an Operator Presence Control Bar that must be held against the handle to enable the spark. Disconnect it at the coil and see if that solves the problem. Here's the manual if you don't have it:

Craftsman 917378531 User Manual Gas, Walk Behind Lawnmower - Manuals And Guides L0210122

User Manual: Craftsman 917378531 917378531 CRAFTSMAN Gas, Walk Behind Lawnmower - Manuals and Guides View the owners manual for your CRAFTSMAN Gas, Walk Behind Lawnmower #917378531. Home:Lawn & Garden Parts:Craftsman Parts:Craftsman Gas, Walk Behind Lawnmower Manual

usermanual.wiki

 

[leggot]

I tied the bar down with a rag, so I think that should work

 

[tabora]

I tied the bar down with a rag, so I think that should work

Not if the Control Bar is defective. Do what I said above...

 

[leggot]

The ground wire is unplugged, still don’t see a spark

 

[leggot]

this wire goes to a the mechanism attached to the bar to enable to lower

 

[tabora]

The ground wire is unplugged, still don’t see a spark

Assuming you've removed the wire(s) from the coil's ground tab as suggested, the only things involved in creating spark are:
1. The magnet in the flywheel that energizes the coil.
2. The flywheel key that determines when the spark is fired.
3, The gap between the coil and the flywheel magnet (0.004-0.006").
4. The coil / spark lead.
5. The spark plug.

 

[leggot]

Hi,

Please see the attached images. One showing that the ground wire is disconnected from the coil and other showing that the stopping mechanism is not engaged. This is a simple machine and shouldn’t be that hard to fix, however it’s unclear to me what the issue is.

It occurs to me the magnets and coil are not engaged correctly to create a big enough of a voltage difference, hence no spark. But I can’t confirm this, my multimeter goes out of range.

 

[tabora]

I replaced the coil...
...Please see the attached images.

That would appear to be the original coil. What happens with the new coil? Is the flywheel key fully intact (not even partially sheared)?

 

[leggot]

I did not purchase a brand new coil, the one I purchased was used but the seller claims that it works. I have tried a couple coils with similar results.

Is testing the ohms on the coil an accurate way to determine if it works?

 

[tabora]

I did not purchase a brand new coil

A brand new coil is $14ish delivered. Why mess around with a used coil?

https://www.ebay.com/sch/i.html?_from=R40&_nkw=%28802574%2C590454%29+coil&_sacat=0&LH_TitleDesc=0&rt=nc&LH_ItemCondition=3

 

[leggot]

Agree, I think this is the same thing, about a buck cheaper: Ignition Coil For Briggs & Stratton 125K02 125K05 125K07 125K09 126M07 126T02 US | eBay

 

[Brad]

OK, this is a dumb question I know and please don't take offense, but when testing the spark plug are you touching the base of it to the engine? What I will do is get my jumper cables and put the clamp on the engine block and the other end on the spark plug.

 

[leggot]

Yes, tested the spark plug on another machine to verify spark. The same when testing on this machine.