656 ignition problem cured

A couple days ago I posted a few questions about the arrangement of the ignition system on a 656. It acted like it wasn't getting strong enough spark to start while cranking and I questioned the resistor arrangement. This thing has electronic ignition.

I talked to the shop foreman at a CIH dealer and he told me the resistor should NOT be connected when an electronic ignition is installed. I've never had any experience with add-on electronic ignition so I was groping in the dark for an answer. Ten minutes with two wrenches,a screw driver and cold fingers and I had the resistor disconnected and bypassed. Hit the starter and after three revolutions it started right up. Hooray! The owner said he didn't use this tractor last winter because it was such a pain to start. He might not use it this winter either, but at least now it's ready if needed. Jim

Thanks for the update. Always good to hear what the "fix" is.

The electronic doodad under the distributor cap only triggers the spark. Spark strength comes from the coil.

I know "they" recommend some super-awesome flame-belching ultra-coil with the electronic ignition conversions. AFAIK they are true 12V coils.

Running straight 12V through the OEM coil will cook it within a few hours.

AFAIK, the 656 is supposed to have a 12V bypass running from the solenoid straight to the coil, so that the coil receives 12V during startup. The starter tends to draw the battery down, which causes a weak spark through the resistor.

Hopefully the owner also popped for the "special" coil when he installed the electronic ignition. Otherwise you will be replacing the coil here in the near future.

Thank you for the information. I can use all I can get LOL. I was wondering about that coil. It appears to be a regular 12V. Yesterday I told the owner I didn't know if this would cook the coil or not, but if it did we'd replace it with one that won't cook. This morning I started it up and used it a little and it wasn't as cold blooded after it was running. Before I went around the resistor I'd have to run it with the choke out a little at first, which is normal, but if the governer snapped the throttle open it'd die on the spot for the first fifteen minutes or so. This morning It ran with the choke partly out as normal, but after a minute or so it wouldn't die when the governor snapped the throttle open. I didn't run it more than a few minutes so I never did warm it up. Like I said in my origional post, there is no evidence of a bypass wire in the harness, though I sure would think there should be one. Jim

(quoted from post at 19:54:49 12/22/11) A couple days ago I posted a few questions about the arrangement of the ignition system on a 656. It acted like it wasn't getting strong enough spark to start while cranking and I questioned the resistor arrangement. This thing has electronic ignition.

I talked to the shop foreman at a CIH dealer and he told me the resistor should NOT be connected when an electronic ignition is installed. I've never had any experience with add-on electronic ignition so I was groping in the dark for an answer. Ten minutes with two wrenches,a screw driver and cold fingers and I had the resistor disconnected and bypassed. Hit the starter and after three revolutions it started right up. Hooray! The owner said he didn't use this tractor last winter because it was such a pain to start. He might not use it this winter either, but at least now it's ready if needed. Jim

Click to expand...

Here is the link to the Pertronix manual.
http://www.pertronix.com/support/manuals/pdf/ignitor12vneg.pdf

From what I can gather, the external ballast resistor is to be used, or not used. I assume it depends on whether the coil being used is a 6 volt coil, which WOULD require the resistor, a 12 volt coil that is internally resisted which would NOT require the resistor, or a simple 12 volt coil which DOES require the external resistor. If a ballast resistor IS used, the wire feeding the electronic unit SHOULD NOT go through the resistor, but the wire feeding the ignition coil DOES go through the resistor.

This coil simply reads 12V so I don't know if it's plain or resister. Since there is supposed to be a resistor on this tractor I assume it's a plain coil and will destruct if I continue to use it this way. We're going to be using it tomorrow for just idling work. After that I'll have a chance to get it back in the shop to check the wireing a little closer to see if I can find a bypass wire that I assume is supposed to be there. Jim

A 12 v coil will have 3 ohms to 3.5 ohms of measured resistance between the Small terminals (when not connected) a 6v coil will have more like 1.5 to 2 ohms. The variability is in the wires used (length and diameter) inside. I know of no resistors inside coils. They would produce heat and that is not desired. The resistors used on 12v coils with external resistor required are built to radiate heat. Ceramic blocks, or long wires embedded in wiring harnesses provide that heat sink. The 6v coils and the 12v coils for use with an external resistor are basically the same coil. Both will have the lower resistance.
The bypass system, from the solenoid or relay, or starter switch, is designed to let the coil operate at cranking voltages between 9 and 11 volts for starting only. this gives hot spark, and keeps the resistor out of the circuit while cranking. (if the resistor was in the circuit, it would lower the voltage to around 4 volts (not reliable) as you have found out.) Jim
More info

(quoted from post at 18:11:59 12/23/11) This coil simply reads 12V so I don't know if it's plain or resister. Since there is supposed to be a resistor on this tractor I assume it's a plain coil and will destruct if I continue to use it this way. We're going to be using it tomorrow for just idling work. After that I'll have a chance to get it back in the shop to check the wireing a little closer to see if I can find a bypass wire that I assume is supposed to be there. Jim

Click to expand...

A 12 volt coil that does not need an external resistor will be clearly marked as such.

I tested a brand new 6 volt universal coil with my ohmmeter, and also tested a brand new 12 volt coil that does not need the external resistor. Both coils had exactly zero ohms of resistance across the positive and negative terminals, and when tested from the positive, OR the negative terminal to the tower, the ohmmeter read exactly 9 ohms of resistance on BOTH coils. Granted, I was using a cheapy ohmmeter which most likely is NOT 100% accurate, but it IS consistent.

I do not have a 12 volt coil that REQUIRES an external resistor, so I could not do that test.