How To Quickly Diagnose The Sneaky Weak Ignition Coil

A quick video to rule out or confirm a weak ignition coil, the symptoms of which present themselves as a fuel delivery issue.
I filmed the spark of a weak coil and a good strong coil which in person you can visually see the difference, but the differences are very subtle and hard to see in the video. So when checking to see if you have spark with a weak coil, you'll see that you do indeed have spark, but under load the spark isn't strong enough to keep up with increased fuel/air mixture and the engine bogs down or quits above idle under load. I'll show how the engine has a hard time starting and running with the weak coil, but immediately starts and runs strong and smooth with the good coil.
I describe the symptoms and behavior of the weak coil, so if you're experiencing these symptoms swap out the coil which is quick and easy to just jumper one in. You'll quickly rule out or confirm a weak coil. If it's not the coil, it's time to check fuel pressure, and fuel filters, or run circuits in the carburetor.

[mosessich]

Thank you for the video! I am just starting to work on my own vehicles since I am only 17. I always appreciate when people share decades of experience!

[kennethhettig]

Great way to test a coil, thanks for posting!

[GoatPilot]

Small pro tjp for anyone here looking for help: For any older electronic distributor ignition, long wires w/ single coil, etc, do this at night or in your garage with the lights off. After you get it running, also check under the hood in the dark for any spark/ignition leaks arcing around the engine from bad/damaged wires, loose connections, bad/damaged/loose boots, damaged/burned through coil, etc.

[eddieconerly]

This is it from New Orleans please more content your delivery is awesome your info is great tell us more about your truck or you keep it running good so I can learn from you thanks

[garrettpolzin]

I’ve been trying to find a “fuel issue” for 3 weeks. I cannot wait to test my coil I have a pretty good feeling this is issue. You described my exact issue

[barryallenporter]

Good video. I always forget the simple things and overcomplicate issues.

[michealphy]

My HONDA CIVIC 1985 . took me 1 month been through 2 garages unable to diagnose the problem . Thanks alot for this information

[nelsonluke-sexp]

Thanks for that I'm leaning for coil symptoms.

[ryantabussi]

extremely helpful and good explanation thank you very much

[melvis]

Thanks for the great job very good explanations and the great humor Thanks again for sharing with us all 🇩🇰👍

[ReedMJones]

Excellent Symptoms Description! Thank You.

[hammerheadable]

Thank you so much!!! I think now I don't have to push it into the parking lot by the mall, helping my son.😂😂😂

[gregander]

I don't know about that spark color issue, however there may be a difference between the two coils in terms of voltage.

[eddieconerly]

Man this is Eddie in New Orleans this is the second time you didn’t help me I have a 83 4150 you help me with the gas tank and now you help me with the coil cause my truck is doing the same thing that you describe thanks

[cbscherger]

It'd be interesting to see the difference in primary & secondary resistance between the 2 coils.

[TheJaredsalinsky]

This is very helpful. My ‘78 carbureted Ferrari is having that same ‘chugging’ and ‘hesitation’ when starting. And it takes a few times to get it started. Sounds exactly like your Ford! Can you ‘fix’ coils? Or clean them? Or do you just have to replace them?
Thanks!

[waynecox]

Thank you brother i am trying to fix my 60 classic ford i am stumped its doing exactly what you described so im thinking faulty coil

[Noliftracingbro]

Gotta 95 mustang gt it's doing the same thing I already have a new pump and assembly haven't put it in yet... And a new coil gonna try the coil in the morning

[dylanjames]

Off to the parts store, my dads 1981 xd ford falcon with a 351 Cleveland electronic ignition coil just died😅 it gives blue spark off the plug has fuel but will not even cough the car ran perfectly when last parked up. So new coil before i get any further with the ignition system.

[billyganoesr]

I thought a blue spark is a hotter spark than an orange spark