How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask J.R. Your Own Question
J.R., Small Engine Technician
Category: Small Engine
Satisfied Customers: 7445
Experience:  Owner of outdoor power equipment business, repairing all makes and models.
Type Your Small Engine Question Here...
J.R. is online now
A new question is answered every 9 seconds

How to measure resistance on an ignition coil, such as from

Customer Question

How to measure resistance on an ignition coil, such as from plug wire to coil ? Will this test the coil ?
Submitted: 8 years ago.
Category: Small Engine
Expert:  J.R. replied 8 years ago.
What make and model of engine are we dealing with?
Customer: replied 8 years ago.
Shindaiwa LT-20 Trimmer with a S20EL engine and a 70030-71600 ignition coil...I think. I cant get the plug to fire. I mounted the coil to another trimmer to see if the magnets would excite the coil to fire but nothing, I am wondering if the insulation has weakened inside the coil causing a short inside, although it measures high resistance 8K ohms I read 2 other small weed-trimmer coils at 5K ohms (different mfg) . Either Shindaiwa coils are a higher resistance or the insulation inside the unit has weakened? Maybe I just need to install a new coil.
Expert:  J.R. replied 8 years ago.
The only way to test the coil without an expensive ignition tester ($1000.00) is to unplug the small wire from the coil and then check for spark. If you do not have a good spark with the small wire unhooked, then the coil is likely bad.