SHOP PRODUCTS
Houzz Logo Print
clifh21730

No Spark Mystery in an old engine.

clifh21730
12 years ago

The engine is on a very old (manufactured in the early 1960s) Sears garden tractor. The engine is 17 hp, cast iron horizontal shaft model: 325431-0139-01-711010

The problem is as follows:

About 8 years ago, the tractor was developing one problem after another, so when it lost its ignition spark, I parked it and bought a new one.

A few days ago, I pulled it from the barn and set out to fix the spark problem then to restore the tractor to near-new status. I replaced the coil, points, plug and condenser and it started right up with a good hot spark. Much to my surprise. I started and stopped it several times over a two day period. Then, all of a sudden, it refused to start. No spark. I reset the coil/flywheel gap (.013), points (.020) and plug (.030). No help. I checked the terminal between the coil and points (mounted on the housing) for shorts. None. I even bypassed it to be sure. I disconnected the shutdown wire just in case there was a problem in the ignition switch. No help.

I did note that there was a very - emphasize very - little spark when the plug wire is held next to the head. It is so weak that it can only be seen in darkened conditions. Thinking that it is possible that the condenser might -just might - be defective, I replaced it with a new one. No help. Finally, I gave up on frustration and hauled to a small engine repair shop owned by a friend who has been around a long time and is very familiar with point/condenser ignition systems.

He started out feeling very confidant that, since the only components were points, condenser, coil and plug, the problem would be easy to solve. Not so. We then replaced the coil-to-points wire, thinking that, since the insulation was old and stiff, it just might be the problem. No help. He then dug out his old test instruments and tested the coil and condenser. Tested very good. We replaced the points again (even tho they were new). Still no help.

Someone suggested that I should sand the rust from the Magnet. Did that. Sanded the entire flywheel. No help.

Things seem to point to the coil, even tho it is brand new. However, the question that would come up is: What could cause a new coil to go bad? I hesitate to order a new coil just yet because of the unnecessary expense if that isn't the problem.

Can anyone shed light on this mystery or offer a new approach?

Comments (13)

Sponsored
Zanesville's Most Skilled & Knowledgeable Home Improvement Specialists