Ferris IS3000Z new coil - no spark - How do I find a dead short

Just making sure....

Okay are you leaving both kill wires attach to coils? I know you said you disconnected the kill wire but could have done somewhere else. If so the coil that firing can be the one that is bad.

Otherwise there is no way a short in the harness would be killing the coil as it would be isolated from the harness.
 
I pulled this wiring diagram below off a Google search. I do not know if it is yours or not but it was in the owner's manual so it would be easy for you to confirm it. The wiring shows the grounding kill wires coming from each coil in a Y to a single wire that goes back thru a connector to the B terminal on the switch.In the off position the B wire is connected to A, which is ground - thus killing the coils. If your engine runs with the kill wires to both coils removed, but one cylinder does not have spark, one might suspect a bad plug, or a bad coil. Also coils need a ground and occasionally the ground can be bad - corrosion. If swapping the coils and plugs does not change the behavior as to which cylinder runs, then I don't know what to say. You might have found a new law in physics or have spark and not know it - making the problem one of missing compression or fuel to air ratio. James Condon had one recently that was down on one cylinder, and it was a broken connecting rod on one side.

wiring.jpg
 
Last edited:
sgkent said:
does the harness have diodes in it? Are there any electronics involved? I only ask because some other mowers that have coil issues actually have a bad diode. I have no idea what your model has or does not have. Only throwing the question out there.
Click to expand...
Diodes are internal to the coils.
 
StarTech said:
Just making sure....

Okay are you leaving both kill wires attach to coils? I know you said you disconnected the kill wire but could have done somewhere else. If so the coil that firing can be the one that is bad.

Otherwise there is no way a short in the harness would be killing the coil as it would be isolated from the harness.
Click to expand...
I took off both kill wires and it still only fires on the right side.
 
Rivets said:
If you would read the instructions in the manual you would see that it says to remove the coil. Second, the secondary readings say the ohms are K, which means thousands.
Click to expand...
On my new coil
A to B on Primary is 5.60 (Manual says it should be 16-24)
A to C on Secondary is 21.22

When I took it off, I noticed I was sent the wrong part. The box said 1 (left side) and the part description said 1 and pictured was a 1, but I received a 2 (right side). I read that these are not interchangeable. What do you think?
 
StarTech said:
Diodes are internal to the coils.
Click to expand...
Just went through something like this on a 731. The original coils on older engines have internal diodes. The aftermarket coils don't have diodes. Not 100% sure but the internet says the new OEM coils don't have diodes. I had a bad coil and couldn't get a new non diode coil to work with the existing good coil. Wound up installing 2 new aftermarket coils that were identical and installing a diode on one coil. The same coil works on both sides.
 
Have the mounting screws been replaced with gold anodized screws? They should be black oxide finished.

If the replacement coil came with new mounting screws, they are suspect. I have had that happen to me recently.
 
You must log in or register to reply here.
Back
Top